hot water heater safety valve factory

If you’ve been having issues with your water heater recently, you might find that you’re paying high energy bills, not getting access to hot water when you want it, or your water pressure is low.

Fortunately, by understanding how relief valves work, you can solve whatever problem you’re having with the one on your water heater. In this article, we’ll review everything you should know about this valve.

A water heater pressure relief valve, also referred to as a T&P valve, pressure relief valve, or water heater temperature valve is a safety feature that you can find on any water heater. The reason it’s there is to keep you safe in case the water pressure is too high.

Without this safety feature, your water heater could end up breaking. You could potentially end up with burns if the high water pressure is dangerously high.

This valve also ensures that there aren’t any leaks in your water heater, which would lead to low water pressure when you want to use it to wash the dishes or take a shower.

The water heater pressure relief valve is in place so that it can relieve excess pressure and temperature in a water heater if either of these is too high. Because this everyday appliance is a closed system, thermal expansion occurs in water heaters.

Here’s how it works. Whether your water heater is heated by electric elements or a gas burner, both the metal tank and the water inside expand when the hot water temperature is somewhere between 120 and 140 degrees.

It’s totally normal for the water and water heater to expand to a certain extend. After all, this is what naturally happens when the temperature rises.

However, when the temperature is 210 degrees—or the pressure is 150 pounds per inch (psi)—this is far too much pressure and heat in the water heater. If it’s the case, you should change your hot water heater temperature.

If your water heater pressure relief valve is working, this is when it will open. This releases steam and hot water from the discharge tube, making your water heater operate safely again.

On the micro-level, the functioning of this valve works like this. The relief valve itself has been set up by a professional or pre-designed to open when the temperature or pressure reaches a dangerous level.

When functioning properly, it will open as it’s designed to when the levels of heat or pressure are high. The liquid comes out through this auxiliary route, relieving the heat and pressure within the water tank.

This specific state that the water heater is in is called the “blowdown.” Usually, the “blowdown” is defined by professionals (and is used in the design or set up of the valve) as a specific pressure percentage.

The “blowdown” is usually somewhere between 2 and 20%. Once the pressure has reached the “blowdown” amount, the pressure relief valve will close again so that you can use the water heater as intended.

If you’ve been noticing any issues with your water heater pressure relief valve, then you need to know where it is on your water heater. Usually, you can find it on the top or side of this appliance. It’s a valve that’s connected to a plastic or metal discharge tube that points up.

The water heater pressure is already installed when you receive your water heater (or buy a home that has one already). It’s actually welded onto the tank; you’ll see a threaded inlet where it is.

This is for safety reasons. Everything has been done according to standards that have been mandated by plumbing codes. So if you’re having any issues with the valve, you’ll have to call a professional to have it fixed.

This said, if you’re only having issues with the discharge tube, this is easy to replace. You won’t have to drain or power down your water heater, and you can deal with it yourself.

This said, considering that there might be other issues causing discharge tube problems—issues connected to high water pressure or temperature—it’s safest to have a professional deal with this too.

If you suspect there’s a problem with your water heater pressure relief valve, you can do a test. This is actually good idea if you don’t have any problems at all, as this type of maintenance will protect your water heater—and yourself.

To get started, identify where the relief valve shut off is. Usually, you can find it upon the cold water feed, which is on top of the water tank, on the right side where the inlet is.

Finally, release the level so that it quickly snaps into the original position. If it doesn’t snap quickly into this original position, then your water heater valve isn’t working and needs to be replaced.

When your water heater pressure relief valve isn’t functioning properly, it’s usually for one of to two reasons. It either sticks so that it doesn’t properly open or close, or it has a leak, which means that it’s continually dripping, lowering your water pressure.

If your valve is sticky, then it becomes stuck in a closed (downward) or open (extended position). If it’s closed, then the valve won’t be able to relieve the heat or pressure that builds up in the closed water heater system. There could be a rupture as a result.

Sometimes, you can easily fix this problem by opening and closing the valve lever a few times. However, if it continues to stick, then you’ll need to replace it.

Your water heater is leaking? Make sure that it doesn’t come from the valve before replacing it. If your pressure relief valve is leaking, then this maybe because it isn’t seated properly in the tank’s threaded opening. This is quite a common issue if you’ve recently replaced your old valve with a new one. To fix this issue with this cause, you have to take several steps.

If the lever snaps into its original position and it’s still leaking, you need to turn off the gas valve by turning it to the off position. Then, shut the water off so you can replace the valve safely.

If a water pressure issue is what is causing the water heater pressure relief valve to not work, then it might be dangerous for you to change the valve yourself. Generally speaking, it’s a good idea to hire a professional to protect yourself.

Now that we’ve reviewed everything you should know about a water heater pressure relief valve you might have realized that you need to replace your water heater valve. However, to be as safe as possible, you want to hire a professional.

Temperature and pressure relief valves are used in residential and commercial water heater and hot water storage tank applications to provide automatic temperature and pressure protection to hot water supply tanks and hot water heaters. We have a full-line of products in multiple sizes, pressure ratings, and inlet/outlet types.

Year after year, your water heater serves an important role in your home. Your morning routine just wouldn’t be the same—or nearly as comfortable—without hot water. Yet, water heaters and their components do not last forever. Preventative maintenance is the key to ensuring that your water heater continues to safely provide your home with hot water. In this article, we’ll review a critical safety component of your water heater, the water heater pressure-relief valve.

If your water heater has stopped working, fill out the form to schedule a free VIP plumbing inspection here in the Chicago area. Our plumbers are available 24/7 to help you and your home!

The name is actually quite literal. It’s a valve that relieves excess pressure in the water heater tank. By doing so, it can prevent excess pressure buildup that has the potential to cause a tank burst and flood your home. It’s an unheralded but essential safety mechanism for your water heater.

As your water heater heats up the water in the tank, the water expands and steam is generated. The greater the heat, the more expansion that occurs. This expansion puts pressure on the exterior walls of the tank, but this is to be expected. Some degree of excess pressure escapes through the water pipes connected to the water heater. In the event that it cannot, the pressure-relief valve triggers. By releasing some of the hot water and air, the valve lowers the pressure back down to safe levels.

If the pressure-relief valve is unable to open, the pressure can continue to build inside of the tank past that 100 PSI ceiling. The heavy metal tank can withstand a lot of pressure buildup, but it eventually has its limits. The results are explosive, as the tank gives way, sending hot water flooding outward.

If your water heater has an emergency shutoff valve installed, the burst will be detected and the water supply will automatically shutoff. If not, you’re potentially looking at a flooded home with significant and costly water damage.

So, what causes the pressure-relief valve to fail? In many cases, the valve gets stuck or frozen in place due to the buildup of rust and corrosion inside the tank. Or, the valve is stuck due to a prior instance in which it released hot water.

A broken valve is something that should be fixed right away, but—unless you’re examining your water heater closely on a regular basis—may not be something most homeowners notice. That’s why regular testing and maintenance is important.

We recommend that homeowners here in Chicago test their pressure-relief valve when they flush out their water heater twice every year. Bundling your water heater maintenance tasks together makes sense, since each of these tasks takes about 10 minutes to complete.

Start by positioning a large bucket underneath the valve. You are going to release some hot water during this process, so you want to make sure you’re wearing safe clothes to reduce a scalding risk. Remove the drain pipe attached to the pressure valve.

Then, gently lift the valve switch so that hot water begins to come out of the valve and into the bucket. For the purposes of this test, don’t push the switch all the way up.

So long as water and air are coming out of the water heater during this test, your water heater pressure-relief valve is working as intended. On the other hand, if you’ve flipped the switch up and you’re not seeing any release, that could indicate a problem with the valve.

Did you know that most people use between 80 and 100 gallons of water every day? From using the restroom and showering to cooking and cleaning, your water usage is a crucial part of your daily home routine. Here are just a few daily tasks most homeowners do without thinking, and the corresponding amount of water it takes to complete them: Flushing a toilet: 1-3 gallons per flush

This doesn’t take into account washing your hands, taking a bath, or watering your lawn. Your water use may also skyrocket during the summer, when you’re drinking more water or cooling off in the sprinklers.

Taking all this into account, it’s crucial that your water systems are working at their full capacity. Your water heater delivers hot water to your home, and your water pressure needs to be sufficient for your appliances to work and for your showers to be comfortable.

For all your daily tasks to run smoothly, water pressure is especially important. Imagine not having enough water pressure to flush a toilet or take a shower. There are other consequences to having water pressure that is too high.

To get your water pressure checked and adjusted by a professional, call the team at King Heating, Cooling, & Plumbing in Chicago, Illinois. We’re the experts on all home systems and can make sure your home is running at 100% capacity.

It’s been a long day at work, and you want to come home, take a hot shower, and relax with the family. You turn on the shower to see a small stream of water—or droplets—coming from the shower head. Even when you turn the shower handle to full capacity, only a small amount of water drips out. What’s the problem?

Your water pressure is likely too low. This can be an annoying setback for many homeowners, who depend on high water pressure to shower, clean, cook, and more. How can you properly shower or wash your hands when only a few drops are coming out of the faucet?

On the opposite side of the water pressure spectrum, high water pressure can pose a danger to you and your family inside the home. When water pressure is too high, pipes can become damaged and systems can overwork themselves to bring that water to you. It’s just like the tale of Goldilocks and the Three Bears: you don’t want your water pressure too low or too high—you want it just right.

Low water pressure is usually just a nuisance to homeowners and doesn’t pose a serious problem. High water pressure, on the other hand, can damage fixtures, seals, joints, and more. Water pressure that’s too high can also waste a lot of water in the home, leaving you with a higher utility bill at the end of the month.

As it comes from the municipal water supply to your home, residential water generally ranges from 40 to 80 PSI (pounds per square inch). Anything above or below this range could be considered too low or too high. Some experts will say that any level above 60 PSI is too high of water pressure for your home. It’s best to speak with a professional plumber to get your water pressure checked and to learn more about what level is right for your home. Your PSI range can be affected by elevation, house size, water needs, age of your home, and other factors.

If you haven’t checked your water pressure level in a while, it may be time to call King for a free VIP plumbing inspection. Even if you feel your water pressure and water heater are working great, there could be hidden efficiency problems lurking underneath the surface, such as a water heater that is running too hot and wasting energy. Only a true plumbing professional can get to the bottom of the issue and help you save money, month-over-month.

This goes without saying, but if you’re not comfortable flushing your water heater or checking the valve, don’t just ignore this crucial maintenance need. Give our team a call and have us out to your home to perform this service for you. Remember, this preventative maintenance can help prevent a tank burst and major water damage.

It can be all too easy to forget about your water heater when everything appears to be working correctly. However, a stuck or faulty pressure relief valve could allow the pressure inside your tank to reach dangerous levels — with potentially explosive results. Therefore, testing your water heater pressure relief valve should be at the top of your home maintenance checklist.

You don"t need to be a professional plumber to check your water heater"s safety mechanisms. With the right knowledge, even novice DIY-ers can test their water heater pressure relief valves.

A water heater pressure relief valve is exactly what it says on the tin: a safety mechanism that prevents excessive pressure from building up in your water heater"s tank. Without it, there would be a risk of the tank bursting and flooding your house. A bursting water tank can also cause serious injury and damage to your home"s structure, so keeping the pressure relief valve in good working order is essential.

Pressure inside your water tank occurs when the water expands and produces steam as it heats. The hotter the water, the greater the potential for high pressure. Although some pressure is normal and can escape through the pipes supplying your fixtures, the pressure relief valve activates when the pressure exceeds safe levels. It releases some hot water and steam until the pressure level normalizes.

A water heater pressure relief valve is a short, flat lever attached to a pipe running through the water heater. Its location varies depending on what water heater model you have, but you can usually find it above the tank or high up on one of the sides.

Sometimes, a water heater"s pressure relief valve can get stuck due to a build-up of deposits. Corrosion can also damage the valve and stop it from working correctly. A stuck or broken valve could allow the pressure inside your tank to exceed the safe limit, so it"s crucial to test it regularly.

You can test your water heater pressure relief valve by opening it slightly with a bucket underneath to catch dripping water. Don"t force the valve open if you feel resistance. You"ll know that your valve is working properly if you can see or hear water and gas escaping. If you can"t see water escaping, or you can"t turn the valve easily, it"s time to call a plumber to repair or replace the valve. You should also call a plumber if you see signs that the valve is leaking, such as water pooling on the floor under the tank.

Sometimes, a water heater pressure relief valve will start leaking after you test it, even if the test shows that it"s working correctly. You can often solve this problem by gently opening and closing the valve a few times to remove any deposits stopping it from shutting. Call a plumber to check and repair the leak if this doesn"t work.

You should test your water heater pressure relief valve once or twice each year. The more often you check the valve, the higher the chances of detecting a problem early and preventing a costly leak or burst tank.

One of the most effective ways to prevent problems with your water heater"s pressure relief valve is to ensure that the drain line is installed correctly. It should angle downwards and match the valve"s exhaust port size to allow water to drain properly and prevent corrosion. It"s also essential to use a drain line made from heat-resistant material, like copper. You should call a plumber to replace the drain line if you"re concerned that your installation is incorrect.

Insulating the drain line can stop it from freezing in cold weather. A frozen drain line will stop the pressure release valve from functioning correctly, even if it"s otherwise in good condition.

When you open a water heater pressure relief valve, the water that drips out will be very hot. Therefore, it"s essential to wear protective gloves and eyewear and avoid opening the valve all the way. You may also wish to consider wearing protective clothing to protect your skin against burns.

You will need to replace your water heater pressure relief valve if it"s stuck or damaged. A plumber can tell you whether it"s best to repair the valve or replace it altogether. Furthermore, it"s wise to replace the valve every five years or so, especially if it hasn"t been tested recently.

Water heater temperature and pressure relief valves, or T&P valves, are a safety feature found on all tank water heaters. The valve should always be in good working order to ensure the water heater is safe in the event of extreme pressure buildup. It’s designed to open temporarily and discharge short spurts of water when the temperature exceeds about 210 degrees F, and it releases pressure if the tank gets above 150 psi. It’s important to locate your hot water heater pressure relief valve so you can test it at least once a year and address leaks as they occur.

The T&P valve is usually located high on the side or on top of the tank. It’s connected to a pipe that runs down the length of the water heater and stops a few inches above the floor. The valve itself consists of a flat, inch-and-a-half-long lever that lifts and lowers when water is released to reduce the temperature and pressure within the tank.

It’s recommended that homeowners test the hot water heater pressure relief valve at least once a year to make sure it’s functioning properly. Now that you know where the T&P valve is located, you can test it with ease.

The most important test is to ensure the T&P valve operates correctly. If it doesn’t, pressure could build up inside the tank and become a safety hazard.

Before you test the T&P valve, make sure a pipe is connected to it that guides discharged water to a floor drain or basin below. Then, lift up on the lever and listen for water discharging from the tank and exiting the pipe near the floor. This indicates a successful test and tells you the valve is working correctly.

If water doesn’t discharge from the valve, or the lever is stuck in the closed position (don’t apply excessive force to open it), this could mean naturally occurring mineral deposits are blocking the waterway, rendering the valve inoperable. Turn off the water heater and call a plumber immediately to replace the valve.

If you hear the sound of trickling water coming from the hot water heater, the T&P valve may be leaking. This could mean the valve is defective and needs to be replaced. It could also indicate that the water pressure regulator valve or thermostat is faulty. Or it might mean the valve is doing its job by releasing excess pressure inside the tank.

All of the potential reasons for a leaky T&P valve demand attention, but first you must test whether your valve is leaking. Check for water pooling around the tank. Then, touch the drain line with your hand to see if it feels warm. If so, this is where hot water is leaking out of the tank. Hire a plumber to determine the cause of the leak and replace the hot water heater pressure relief valve if necessary.

Many manufacturers require an inspection and replacement of the T&P valve every two to four years, depending on local water conditions. Any signs of corrosion or scaling indicate the need for an immediate replacement.

If you notice problems with your water heater, or you can’t remember the last time you had the pressure relief valve inspected or replaced, contact Mr. Rooter Plumbing to schedule water heater repair today.

On the side or top of your water heater tank is a valve connected to a metal or plastic discharge tube pointing downward. The valve is called a T&P valve, or TPR valve, for "temperature and pressure relief."

If all goes well, a TPR valve never gets used intentionally except during testing. But in the event of an emergency or malfunction, this valve is of critical importance. It can potentially prevent your water heater from exploding. Understanding how a T&P valve works will help you keep your water heater in tip-top shape and prevent possible damage to your home.

A T&P valve is a valve with an attached tube located on the outside of a water heater. The valve provides relief to the water heater if the pressure exceeds normal operating limits, usually 150 psi.

Mandated by all plumbing codes, the T&P valve relieves excess temperature and pressure in a water heater if either reaches a critical point. A water heater is a closed system, and thermal expansion is an inescapable fact of both normal and abnormal water heater functioning.

In a standard water heater, the water is heated by a gas burner or electric elements. As the water reaches temperatures between 120 and 140 degrees Fahrenheit, both the water and the water heater"s metal tank expand.

Some expansion is normal, but too much expansion is unsafe. When the temperature reaches 210 degrees or the pressure reaches 150 psi (pounds per square inch), a properly functioning T&P valve opens and expels hot water and steam through the discharge tube.

When you purchase a water heater, the T&P valve generally comes pre-installed. A threaded inlet is welded onto the side of the tank. This inlet cannot be removed or replaced. The T&P valve is screwed clockwise onto that inlet.

Because the T&P valve is rarely used, mineral build-up can cause it to stiffen over time. This is a significant safety hazard because, in the event of a temperature or pressure spike, the T&P valve may not open as it should and the water heater might explode.

Water heater manufacturers recommend regular checking of the T&P valve. Wear closed-toe shoes to avoid scalding. Except for a bucket, no tools are required.

Before you begin, make sure you know where the shut-off valve of your tank is. It"s usually located on the cold water feed, on the right side inlet on top of the tank.

Release the lever and let it snap back to its original position. If the lever does not snap back into place, the valve is faulty and must be replaced.

In most cases, there are two problems you might have to address with the T&P valve: a valve that leaks by constantly dripping or a valve that sticks and doesn"t open and close properly.

When a T&P valve is leaking, it may be due to the valve not being properly seated in the threaded opening of the tank. This is especially likely if the leaking occurs immediately after an old valve is replaced. This can be remedied by shutting off the water heater and letting it cool down completely, then removing and rethreading the valve into the tank"s opening.

If the valve is leaking due to dirt or sediment trapped in the relief port, pull the metal spring lever back again and discharge water into the bucket. Once the lever snaps back again, if the water fails to stop completely, shut turn the gas valve to the off position and shut the water off to replace the valve.

A water heater that periodically discharges hot water and steam from the T&P valve may be set to a water temperature that is too high. Make sure that the water temperature setting is in the normal recommended range—about 120 degrees Fahrenheit—or no more than about 150 degrees Fahrenheit.

When stuck downward, the valve cannot provide relief if the system reaches maximum pressure. As a result, the water heater tank might rupture. When stuck in a fully extended position, the T&P valve will continually leak water down through the discharge tube, potentially flooding the home.

The stickiness of the valve can sometimes be remedied by simply opening and closing the lever several times. Jiggle the T&P valve by gently pulling the lever towards you. Much like jiggling a toilet handle, this action may be enough to unstick the valve. If this does not fix the problem, replace the valve.

However, some caution is necessary whenever working with a water heater, because the T&P valve can become damaged if the water heater has exceeded maximum pressure or temperature levels. If you suspect a pressure-related problem with your water heater tank, hire a licensed plumber to have the water heater inspected.

Here at we discuss temperature and pressure relief valves used on residential water heaters. We explain the function, inspection, and maintenance of temperature & pressure relief valves on water heaters used to produce hot water for washing and bathing.

We describe how to diagnose and cure just about every problem with T&P valves on water heaters and we describe how to inspect the hot water supply system for unsafe or improper Temperature & Pressure Relief Valve installation.

Here we provide ANSI and water heater standards and advice: water heater relief valve requirements. Water heaters: how to inspect, test, adjust, repair, and choose among types of hot water heaters.

We offer suggestions for Testing the Water Heater Temperature Pressure Relief Valve (TP Valve or "Safety Valve" or T&P valve or TPR valve) on a Water Heater.

We also describe Water Heater Safety Inspections - how to check the TP Relief Valve, and we warn about BLEVEs: Boiling Liquid Expanding Vapor Explosions at Water Heaters (or heating boilers).

To reduce the risk of abnormally high and dangerous pressures in the hot water system and to reduce chances of a dangerous explosion, water heater manufacturers, building codes, and independent standards require that a temperature and pressure relief valve be installed on the water heater - a T&P Relief Valve.

The T&P Valve installed on your water heater must be marked with a "set pressure" (the pressure at which the valve will open to relieve pressure) must be equal to or less than the maximum working pressure of the water heater.

This is an unsafe condition as the operation of the temperature or pressure relief valve may be interfered with by the insulation and also because the valve cannot be inspected for evidence of leaks or failure.

The water heater temperature/pressure relief valve is installed into an opening directly on the water heater at a location marked for that purpose, usually at or near the top of the heater (where water temperatures will be greatest).

For conventional residential and commercial water heaters of size 15L (4 US Gal) and larger, a pressure relief alone cannot prevent a water heater tank explosion.

Pressure relief valves are only intended for protection of tanks that are not heated - such as a well water pressure tank or a cold water storage tank. Where a pressure-only relief valve is to be used it should be installed as close as possible to the equipment it"s protecting.

The operating pressure and temperature ratingof a temperature/pressure relief valve must be matched to the input BTUh, temperature and pressure capacity of the calorifier, geyser, water heater and its physical volume.

On some very small point of use electric water heaters (1.5 - 3 KW heating capacity, and up to 15L / 5 USG water capacity) the relief valve may operate only on pressure and may be set to open at 6 bar (87 psi).

Question: I went and looked at a house today. On the water heater, there was a tag, it was red and white. It stated "notice of unsafe condition". However on the check boxes there was nothing checked IE stuff like CO or ignition risk. However, on the bottom it said "no water, copper through floor".

Christian, Without some photos or other details, I don"t know, but I speculate that if the discharge tube on the relief valve is piped down through the floor to a non-visible location, that"s improper & unsafe and may be what the tagged meant.

All pressure/temperature relief valves include a tag or label that indicates the valve discharge capacity in BTUs - heat energy discharge rate. The installation or technical data or data tags for all modern water heaters include the water heater"s BTU input rate capacity (and some indicate the specifications for the TP valve too.)

The Temperature/Pressure relief valve for a water heater must have a BTUh discharge rate (BTUs per unit time, such as BTUs per hour) that isequal to or greater thanthe BTU input rate of the heating appliance the valve is supposed to be protecting.[10]

at BLEVE EXPLOSIONS, it is the release of heat (or "temperature" or "energy") that prevents a water tank from exploding when it is being overheated, not the release of pressure.

The Temperature/Pressure relief valve mouth must point down, and a 3/4" I.D. (or greater) discharge tube must be attached to the T&P Valve"s opening and routed down close to but not touching the floor level, typically near a floor drain and stopping 6" above the floor.

Our photo above illustrates a T&P valve installed on the water heater top and connected to a discharge tube that passes outside the building through the wall.

This Tucson Arizona home installation disposes of any water heater T&P discharge outside to about 6" from the ground surface - not to a hidden location. And because there is no freeze risk in this climate the local installation was approved.

T&P valve discharge tubes are permitted to discharge below the floor of a structure but should not be piped to a hidden location where you won"t notice that the valve is dripping or leaking.

What is the minimum clearance distance that is required from the bottom of the countertop to allow the temperature relief valve adequate clearance? Is there a code spec for this?

Julie a look at installation details for TP valves on water heaters didn"t come up with an over-head clearance, though some common sense would indicate you"d need enough space for the test lever to be operated AND enough space to remove and replace the valve when needed.

Since a top-mounted TP valve has a temperature sensing stem that protrudes downwards into the water heater the removal space will be more than you think

On a small water heater (cylinder) the extension of the sensor is about 3" while on larger water heater cylinders that added length could be as much as 9" below the inlet.

Adding that 9" of sensor to the TP valve body and lever height (anywhere from 5 5/8" to 9 1/4") means the minimum (for the smallest valve size) valve total length is about 9" and the larger valve could be much larger.

Now we can slightly tip a valve to get it out of the heater, buy - I"d like to see 12" or more to give both working space and space to remove the valve.

Relief valve missing its discharge tube or drip line, also called an extension tube: this is an unsafe condition - someone may be scalded should the relief valve open.

do not install a temperature & pressure relief valve through any intermediary plumbing fittings. Doing so can cause the T&P valve to fail to operate safely when it should. For example, an air pocked in a coupling can prevent proper sensing of water temperature.

We inspected a hot water tank installation at which the installer actually cut off the temperature sensing probe from the T&P valve so that he could install it through an elbow. This was a stupid and dangerous modification. - Ed.

The discharge tube attached to the water heater pressure/temperature relief valve should be the same diameter as the opening of the valve itself. In our photo someone has fastened a 1/2" pipe discharge tube onto a 3/4" diameter relief valve.

Watch out: As our photo shows (above left), mineral salts left behind as hot water evaporates from the mouth of a pressure or temperature relief valve can completely clog the spring that is intended to allow the relief valve to open under excess (unsafe) pressure.

Water temperature: the water heater temperatures are excessive. In this case the TP valve is doing its job - find and fix the cause of too-high water temperatures in the system.

Incoming water pressure: the building water supply pressure is too high (over about 70 psi) or periodically water pressure fluctuates and is too high at times

at THERMAL EXPANSION TPR VALVE LEAKS A closed water system with thermal expansion and no means of relief can cause leaks at the pressure/temperature relief valve, such as

A deteriorated gasket inside the relief valve or corrosion on the valve seat can cause leaking at the valve; we find this mess occurring when someone lifts the "test lever" on a older P/T valve that has not been tested or operated for some time.

The increase in plumbing system pressure to a level that opens the TP valve is called "thermal expansion pressure". Watts suggests installing a bypass model water pressure regulator that lets the excessive pressure head back to the street main or building water supply system - a solution that only works if the supply pressure is lower than the T&P relief valve spill pressure - which it usually is.

Water hammer: water hammer or "banging pipes" can also be a source of relief valve drips and leaks. Water hammer causes a momentary very high pressure in the water piping system, sufficient to open a TPR valve for a brief time.

Watch out: a dripping or frequently spilling T&P valve is dangerous because those very leaks can eventually cause the valve to clog and then to fail to open when it should.

In 2020 five people, including a child, were killed after a hot water pipe exploded during the night, flooding a basement room with boiling water. The accident occurred on 20 January 2020 in the Mini Hotel Caramel, located in the basement of a residential building in Perm, Russia. - "Around the World", The Times of India, Times Global section, l p. 1, 21 January 2020. The Times added that at least three other people were hospitalized in the accident.

However there is at least one exception: it may be "normal" to see dripping from the relief valve of certain small 2-5 gallon point of use electric water heaters.

Some small point-of-use water heaters, such as some of Ariston"s Andris Lux point of use electric storage water heaters, include this statement in the water heater"s IO Manual:

Watch out: As our we cited above, mineral salts left behind as hot water evaporates from the mouth of a pressure or temperature relief valve can completely clog the spring that is intended to allow the relief valve to open under excess (unsafe) pressure. Ariston recommends that the water heater shown here be protected from hard water (water high in mineral content).

ariston.com retrieved 2020/04/12, original source: Ariston, Op. Cit., https://www.ariston.com/uk/Electric_Water_Heaters/media/files/830_Andris%20Lux%20UK%20Manual%202017.pdf

Technical note: why must the TP Valve point "down"? Take a look at the photo above. If a relief valve is dripping the deposit of minerals inside the valve will accumulate still more rapidly if the valve points to the side or upwards.

At RELIEF VALVES - TP VALVES we explain that in the photograph above where you see the plaster wall and the foam insulation sprayed around the lever, these form blockages of the test lever on the TPR valve.

Watch out: If the lift/test lever on a temperature/pressure relief valve is blocked from movement that prevents the valve from being tested - a step recommended at least annually by relief valve manufacturers.

Watch out: Depending on the relief valve model and design, a blocked relief valve test lever may prevent the valve from opening in response to pressure or temperature:

The pressure-relief component of a TP valve or of a separate additional pressure-relief valve should be at least 20 to 30 psi above the maximum working pressure in the system. Otherwise you will find occasional "nuisance dripping" at the relief valve due to normal water pressure variations or due to water hammer.

The standard opening pressure for TP valves on residential water heaters is usually 150 psi, and most water heater tanks also have a standard operating pressure of 150 psi.

If the building water supply pressure is above 125 psi, Watts recommends that a pressure-reducing valve be installed to reduce pressure to 40-45 psi so that a standard TP valve set can be used.[10]

Note: we recommend that for most conditions residential water pressure inside the building should not exceed 70 psi. We observe an increase of leaks and drips at faucets and toilets at higher building pressures as the pressure may exceed the design pressure of some plumbing fixtures.

Watch out: as we discuss above, dripping TP relief valves are unsafe. The hazard is that minerals in the water supply accumulate inside the valve during the passage of hot water through the valve assembly.

That accumulation of scale will eventually block operation of the relief valve, causing the relief valve to fail to operate properly if unsafe pressure or temperature occurs in the water heater in the future. The risk, ultimately, is a water heater tank or heating boiler explosion.

The water heater relief valve must be capable of discharging energy (as BTUs) at a rate greater than the input rate of the water heater"s energy source

You can easily verify the TPR valve on your 40 gallon water heater by looking at the information on the relief valve data tag and comparing that with the INPUT BTUH rating of your water heater.

Watch out: the typical water heater relief valve capacity rating and sizing charts assume that the heater is supplied with water at no less than 30 psi.

Because very low supply pressure means low pressure in the water heater tank which means that the valve may not open even at unsafe water temperatures or pressures for the equipment installed in your home.

Water heater relief valves must be listed or approved for their use according to the standards accepted by the country where you live. In North America those are SME, ANSI and CSA (AGA) standards.

Watts WATER HEATER TEMPERATURE & PRESSURE RELIEF VALVE SELECTION CHART [PDF] (1996) Watts Regulator, Water Product Division, Safety & Control Valves, retrieved 2020/11/15 original source: http://media.wattswater.com/F-SF.pdf

For gas, electric or oil storage water heaters under 200,000 BTU/hr. ratingand for compliance with any applicable water heater labeling requirements: Use3⁄4" T&P Valves tested under ANSI Z21.22 with ratings as certified and listed by CSA.

For gas or oil-fired storage water heaters between 200,000 and 730,000 BTU/hr.rating; and for compliance with any appli-cable water heater labeling requirements: Use 1" and over T&P valves tested under ANSI Z21.22 with ratings as certified and listed by CSA.

For ASME installations of gas or oil-firedhot water supply boilers heating domestic water for a storage tankover 730,000 BTU output; and for ASME installations of steam coil storage water heaters: Use 11⁄2" and over, T&P valvestested under ANSIZ21.22 with ratings as certified and listedby CSA.

These are abnormal and potentially dangerous conditions. First, they respond to excessive pressureby opening at the pressure set point of the valve, typically 150psi, to prevent further pressure increase.

Second, they respond to excessive temperature. When the temperature of the water in the water heater reaches 210°F, the T&P relief valve’s internal thermostatic element expands, lifting the valve’s disc off its seat to discharge the overheated water.

We can understand the huge energy release involved in a BLEVE explosion by a quick review of the extra energy required to change the state of water from a liquid to a gas.

At SEER RATINGS & OTHER DEFINITIONS in our discussion of BTUs (British Thermal Units, a measure of energy), we point out that while only 180 BTUs of energy are needed to raise one pound of water at 32 degF to 1 pound of water at 212 degF, a much larger amount of energy, 970 BTUs, are needed to raise 1 pound of water at 212 degF to 1 pound of steam vapor at 212 degF.

This figure is the latent heat of vaporization, the number of BTUs of energy used to raise one pound of water at 212 degF to one pound of steam vapor at the same temperature; in other words, the temperature is unchanged but the state of matter is changed from liquid to vapor. State changes involve large amounts of energy.

But if the safety valve has been damaged, modified, or even omitted (as we saw on our neighbor"s water heater), that condition, combined with overheating can cause a water tank to explode, creating a BLEVE - Boiling Liquid Expanding Vapor Explosion that releases tremendous force and causing extreme damage to a building.

Because repeated heating of the water tank bottom may combine with other conditions (such as corrosion or excessive heating due to mineral deposits on the tank bottom) to produce a weak water heater tank bottom, that is the part more likely to fail in an overheat and overpressure condition.

A failure at the water tank bottom may explain why a BLEVE can produce a water tank explosion that behaves like a rocket, sending the water tank skyrocketing up through a building.

Some plumbers open the water heater pressure/temperature relief valve for this air-in purpose - but there is risk that you"ll later be unable to get the valve to shut fully again - debris can clog the valve seat - sometimes we can stop a relief valve from dripping by tapping on the valve lift rod that protrudes through the valve lift lever

Other plumbers simply remove the relief valve entirely - this is the process recommended by some water heater manufactures such as A.O. Smith. Removing the relief valve makes it easy to inspect this critical safety component itself, and it"s easy to clean or replace the safety valve at that time.

When replacing the relief valve use an approved teflon tape or pipe sealant and work neatly and with care so that there will be no leaks at this location.

One has to consider that the manufacturer would not be likely to include the test-lever feature on relief valves if it had no intended uses whatsoever.

Water heater manufacturers" installation instructions for at least some water heaters advise building owners or maintenance personnel to manually operate the TP valve at least once a year to make sure it is working properly.

Temperature and pressure relief valves should be re inspected at least once every three years by a licensed plumbing contractor or authorized inspection agency to ensure that the product has not been affected by corrosive water condition [sic] and to ensure that the valve and discharge line have not been altered or tampered with illegally.

Certain naturally occurring conditions may corrode the valve or its components over time, rendering the valve inoperative.Such conditions are not detectable unless the valve and its components are physically removed and inspected.

Contact a plumbing contractor for a re inspection to assure continuing safety. Failure to re inspect as directed could result in unsafe temperature or pressure build-up that can result in serious injury or death and/or severe property damage. - Watts Water Corporation, "T&P and ASME Safety Relief Valves", retrieved 8/22/14, original source: http://media.wattswater.com/PG-TP-ASME.pdf

Nevertheless, Ken, I agree with you that while the "easing lever" can be used to open or "operate" a TP valve, that does not promise that the valve will necessarily open at the rated pressure or temperature.

But by making this test you might find by that the valve is "stuck" or clogged and will not operate. Not finding that the valve is stuck is not a 100% promise of proper function but the risk is reduced.

Watch out: Opening or operating the pressure relief valve using the lever is not a complete test and it should not be used by home inspectors nor by anyone who is not prepared to shut down the water heater and replace the TP valve immediately should the valve fail to operate or should it fail to close and stop leaking or dripping after it has been tested using the lever.

52 Questions and their Answers [about] Hot Water [Heaters, Explosions & Water Heater Safety], Watts Regulator Company (1973) retrived anew 2018/10/27, original source: http://media.wattswater.com/f-52qa.pdf

"Residential Gas and Electric Water Heaters: Service Handbook", [PDF], A.O. Smith Water Products Company, 5621 W. 115th St., Alsip IL 60803 USA, Tel: 1-800-433-2545, Website: www.hotwater.com, Email: www.hotwater.com/parts, retrieved 15 March 2015, original source: : http://www.hotwater.com/lit/training/320991-000.pdf

This handbook provides service information for residential gas water heaters that are atmospherically vented and use a thermocouple as their electrical source and to residential electric water heaters having one or two heating elements and common wiring configurations for these water heater models.

"Residential Electric Water Heater Installation Instructions and Use & Care Guide", American Water Heater Co., October 2001, American Water Heater Co., Johnson City, TN, [manufacturer of residential & commercial water heaters, also manufacturer of Polaris/Commercial water heaters], Tel: 800-999-9515, web search 1/12/2012, original source: americanwaterheater.com/support/manuals/res-elect.pdf [copy on file] [Technical review requested 1/25/2011]

More water heater temperature & pressure relief valve (TPR) test recommendations are in the Residential Gas and Electric Water Heater Handbook [PDF] provided by A.O. Smith and linked-to at REFERENCES

A Temperature Limiting Valve that limits the outgoing water temperature to 50 °C in order to prevent scalding. This valve should be checked annually by measuring water temperature at a nearby water taps, making sure that the water delivered closest to the water heater is not hotter than 50 °C .

An Expansion Control Valve is used on water heaters in south and Western Australia where hard water is found, and in some other countries or other jurisdictions.

The purpose of this valve is to release pressure through a separate control so that the safety provided by the Temperature and Pressure Relief valve is not compromised by clogging from minerals should that valve frequently open.

The expansion control valve should be tested every six months, following the same procedure as for temperature and pressure relief valves as we described above.

see RELIEF VALVES - TP VALVES where we include additional relief valve information including for hydronic heating and steam heating boilers used for central heating.

At TUNDISH used in PLUMBING we describe special devices designed to provide an air gap in the relief valve discharge tube and piping: a feature that can permit visual detection of a spilling TP valve if its discharge has been piped to an otherwise not visible location, and a feature that can protect the potable building water supply system against contamination from cross connections.

If the building water pressure gauge reading is ever found at 80 psi or higher, you will want to install a water pressure regulator at the point where water supply enters the building.

If your building already has a water pressure gauge installed, it may be defective or it may be set too high. The articles listed just below discuss how to adjust a water pressure regulator:

An alternative to installing or changing a water pressure regulator when building water pressure is occasionally 80 psi or higher is the installation of an expansion tank to temporarily absorb that pressure increase. Proper use of an expansion tank can help avoid unnecessary opening of the pressure/temperature relief valve on a hot water heating tank or a hot water heating boiler.

A typical pressure/temperature relief valve for a water heater, like this Rheem ProTech TPR valve shown here, costs about $25. for the valve alone - not including paying a plumber for installation.

Note that this TPR valve has an extenstion that senses water temperature by being immersed into the hot water tank or calorifier (or geyser) hot water contents.

By replacing the TPR valve and observing that the new one leaks - i.e. not from the threaded fitting but from the valve"s discharge opening or mouth - you"ve demonstrated that there is an unsafe condition on the water heater itself - an over temperature or over pressure, or possibly a leak due to water hammer or abnormally high water system pressure and the need for a thermal expansion tank on the system.

Water heater temperature and pressure relief valves are not adjustable. You don"t change or set the relief or release pressure. The standard pressure is typically 150 psi.

While I haven"t seen an explicit prohibition against using flexible copper tubing on a relief valve discharge tube, The building codes don"t anticipate every possible dangerous or otherwise are erroneous. Installation that we might come up with.

However in my opinion. A flexile TPR valve discharge tube Is a very bad idea because the flexibility means that the discharge tube could easily be pushed into a position in which, rather than discharging very hot water onto the floor, It could discharge scalding water into the face of someone nearby.

The standard opening pressure for TP valves on residential water heaters is usually 150 psi, and most water heater tanks also have a standard operating pressure of 150 psi. If the building water supply pressure is above 125 psi, Watts recommends that a pressure-reducing valve be installed to reduce pressure to 40-45 psi so that a standard TP valve set can be used.[10]

All this sound strange to me. I acknowledge that an expert appliance or water heater repair person or plumber knows things i don"t but frankly I can"t make any sense out of what you were told.

WhenI first looked at your photo on my smartphone I could not see the smudge that"s visible on a larger screen. And I was more suspicious than now after taking a closer look.

An air leak up inside the heater insulating jacket might indeed carry soot from an improperly-operating gas burner or oil burner to this opening where on escape a smudge might be left.

The possibilities range from a scam - innocent air movement, to an astute technician whom you should buy a steak dinner - if there is an unsafe gas burner or unsafe electrical connection or wiring in your heater.

A tech came out to fix my garbage disposal. Ask to see my hot water heater ( electric). Wiped his finger across the top of temp/pressure valve and said the dirt shows “arching” inside tank, and is a fire hazard. Recommend the entire unit be replaced. Is this accurate, or a scam?

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[3] Pounds of lime deposited vs. temperature and hot water usage: see Purdue Bulletin #74 (also provided by A.O. Smith in the article below). Purdue"s chart shows the number of pounds of lime deposited per year as a function of the water usage in gallons per day, with an assumed 10 grains of water hardness.

[4] "When, Why, and How to Remove Water Scale from Tank Type Glass-Lined Water Heaters (for non glass-lined tanks, consult water heater manufacturer)" PDF provided by A.O. Smith Water Products Company - hotwater.com/lit/training/4800r9.pdf 800-433-2545 - 01/07/2009.

[6] A.O. Smith"s Form No. 4778* All about Deliming Coil-Type/Tube-Type Commercial Water Heaters and Hydronic Boilers *Normally supplied when ordering Part No. 4930 Motorized Deliming Pump Kit

[7] Building Owner Water Heater Safety Notice [PDF] Building Department, City of Colleyville TX, web search 09/24/2010, original source: http://www.colleyville.com/dmdocuments/Building%20

Water heater safety is imperative to the occupants of a building or structure. If improperly installed, water heaters can be detrimental to the structure, as well as being potentially fatal to its occupants. The proper installation of a water heater is so important that according to Texas State Law all water heater installations must be inspected by a state licensed plumbing inspector.

[8] Rheem Electric Water Heater "Owners Guide and Installation Instructions", (Australian models) rheem.com.au/images/pdf/owners_dom-elec_121996C_0707.pdf

[9] Watts, 815 Chestnut Street, North Andover, MA, USA 01845-6098, http://www.watts.com web search 09/18/2010 original source: http://www.watts.com/pages/learnAbout/reducingValves.asp?catId=64

[11] "Four hurt as water heater explodes", Elaine Porterfield, Paul Shukovsky, Lewis Kamb, Seattle Post Intelligencer, 28 July 2001, web search 25 Sept 2010, original source: http://www.seattlepi.com/local/33094_boom28.shtml

In small scale testing, the Mythbusters started with a small six gallon water heater and disabled all of its safety features under the theory of poor installation or neglect. While the water heater eventually ruptured, it did not explode like a rocket. The Mythbusters then upgraded to larger thirty gallon water heater which exploded with significantly greater force, sending the water heater several hundred feet into the air. In order to confirm the stated myth, the Mythbusters obtained a full size fifty two gallon water heater and built a shack around it with a roof that followed standard California building codes. The water heater eventually exploded, shooting through the roof five hundred feet into the air and disintegrating the shack. In light of these results, and the fact that there is documented evidence corroborating the myth, the Mythbusters deemed it confirmed.

Because of built in safety devices most water heaters safely operate day in, day out without any major problems. But don"t let the excellent safety record of water heaters lull you into forgetting about the explosive potential of these marvels of convenience. When a water heater explodes, it releases a tremendous blast force which can easily demolish a building.

Randall Hilton and crew, with help from the Service Roundtable has prepared this video of a water heater explosion as a demonstration of the explosive power of a simple water heater. The hot water tank explodes using the steam pressure that any water heater can generate when the thermostat and temperature pressure relief valve (T&P valve or PT valve) malfunction. We were impressed by how far the tank flew after the water heater exploded. Click on the links below to view the video. Then, visit the Q&A page for warning signs as well as simple steps which can help you prevent your own water heater from exploding.

TECHNICAL REFERENCE GUIDE to manufacturer"s model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop Weldon & Associates

The temperature and pressure relief valve is a safety device that is installed at the factory.  It is designed to open on a residential water heater, for your protection, when there is excessive water temperature or excessive water pressure. There are many things that result in conditions causing a T&P to release water. Thermal Expansion in a closed system is a common cause that is often the last to be considered.

When water heats it expands, just as mercury in a thermometer expands rising up the scale to show you a person’s body temperature. If the expansion of the mercury were to exceed the capacity of the thermometer the thermometer would explode. When water heats in a water heater it also expands. The expanding water will typically push back into the supply line preventing excessive pressure from building inside the water heater.

When a check valve (backflow preventer) or pressure reducing valve is installed without a built-in bypass water is not allowed to push back into the supply line. Pressure instead builds within the water heater. At 150 psi the T&P will begin releasing water to reduce the pressure within the water heater for your protection.  Should this occur we recommend that you install a properly sized expansion tank. An expansion tank helps by absorbing the excess water pressure in a diaphragm tank. The diaphragm allows for water to flow into the expansion tank as it is being heated and expanding and flow back into the water heater at other times. An expansion tank will prevent wasting water released from the T and P during expansion, as well.

Why would a backflow preventer/check valve be installed in the first place? To prevent your home’s water from backing up into the main supply. Removal of the backflow preventer/check valve may not be an option, as it is likely required by codes in your area. Removal of a pressure reducing valve is also not a likely option, as controlling the water pressure into the home may be necessary.

Excessive operation of a thermostat (typically due to points being fused together in a power surge or electrical storm). If the water is overheating in your water heater a thermostat may need to be replaced.

A ground element. If the water is overheating in your water heater an element may be ground within its sheathing, typically due to a power surge of some type, and require replacing.

Pressure surge from the operation of a solenoid valve. If the T&PP only opens when operating the washing machine you may need to install a water hammer arrestor, shock absorber or blind cushion air pipe. An expansion tank may be the answer.

If you’re a homeowner, your family’s and home’s safety become undoubtedly high on your list of concerns. And you want to make sure that dangers at home are brought to a minimum.

Taking a warm shower is one of life’s special little joys, and nothing kills the joy more than an unexpected rush of skin-scalding hot water. On top of enjoyment, safety is also of paramount importance when it comes to water heaters because nobody wants a freak shower accident. Let’s take a look at how Rheem’s storage water heaters are built to make sure that you and your family stay safe during shower time.

Unlike instant water heaters where water is heated instantly, a storage water heater pre-heats cold water and stores it in an insulated tank so that an accumulation of hot water can be readily available to be dispensed at a moment’s notice.

Because water is heated in a storage tank, heating typically takes a longer time. As heating takes place, pressure in the storage tank will gradually rise. If the temperature gets higher beyond expected and the pressure is not released, it may even cause an explosion.

This is where a temperature and pressure relief valve comes in. The purpose of the valve is to allow excessive temperature and pressure inside the storage tank to be released safely. Without the valve, your water heater may run the risk of an explosion if the temperature or pressure got higher than what the tank was designed to handle. To put it simply, storage water heaters can be hazardous or even lethal if they do not come with a temperature and pressure relief valve.

If you’ve ever wondered how a temperature and pressure relief valve looks like, it’s that little lever on the top of a storage water heater. This seemingly insignificant lever is what keeps your water heater from turning into a major safety risk. In case you’re having trouble figuring out how a temperature and pressure relief valve looks like, it looks something like this:

At Rheem, we care about your safety. Other than a built-in system to automatically monitor and control the temperature and pressure, our storage water heaters also come with a relief valve for added safety.

As such, it’s advisable to give your storage water heater some love by lifting the valve every so often to release excessive temperature and pressure—just this one simple preventive measure will keep irreparable damages off and also help your storage water heater withstand the test of time.

The water heater is known for its high heat and high pressure. The water heater temperature-pressure relief valve (TPR Valve), protects us from this high heat and pressure. So what is the TPR valve, why does it leak, and what should you do about it?

The TPR valve, also called, a pressure relief valve is a specialized valve