A water heater temperature and pressure (T&P) relief valve also known as the TPR valve is designed to open up and discharge water from the tank if the pressure and temperature are too high (210 degrees Fahrenheit and 150 psi).
It is the water heater’s failsafe. TPR valves prevent water heaters from exploding. This is why you should never cap the TPR valve’s discharge pipe.
If your water heater temperature and relief valve is leaking, it is a sign that it is faulty, the water pressure is too high, the water heater temperature is set too high or you have a closed loop system and do not have a thermal expansion tank.
The solution for a leaking water heater T&P valve is replacing it if it is faulty, installing a thermal expansion tank if you have a closed system or adjusting your water heater temperature or/and water pressure.
If you are sure that the problem you have with your leaking TPR valve is an old and faulty valve, replacing it with a new one is the only option. Luckily, replacing a water heater temperature and pressure relief valve is easy and you don’t need to hire a plumber.
To replace a water heater T&P relief valve, turn off the water heater and its cold water supply as well. Drain water from the tank to just below the valve then remove it. Apply Teflon tape on the new valve, thread it in and tighten it. Turn on the heater and the cold water.
Ideally, a water heater temperature and pressure relief valve should be replaced every 3 to five years. You do not have to wait for it to start leaking for you to replace it.
The longevity of the valve is hugely dependent on the quality of your water. If you live in area with hard water, mineral deposits will build up around the valve preventing it from sealing.
As a matter of fact, minerals like calcium can completely block off the valve meaning that it will not open up even after water pressure in the tank goes past the limit. This as you can imagine is very risky.
It is therefore recommended that you test your TPR valve from time to time just to be sure that it is working. You do that by simply lifting the lever and checking if water will drip from the bottom of the discharge pipe.
To replace a water heater T&P valve you only need the following:
- New valve
- Teflon tape
- Wire brush/toothbrush
- Adjustable wrench
How to Replace a Water Heater Temperature and Pressure Relief Valve
Follow the following steps to replace your water heater’s T&P relief valve:
1. Turn off Cold Water Shut off Valve
As you replace the valve, you cannot have water flowing into the tank otherwise you are going to flood your basement. That is why you should first turn off the supply of cold water to the tank.
There are 2 types of shut off valves. If you have a gate valve (looks like a wheel), turn it all the clockwise but if you have a ball valve, pull the handle so that it is at 90 degrees (perpendicular) to the water supply pipe.
Note: In the unlikely event that you do not have this valve, you will need to turn off water at the main house water shut off valve. To know where to locate the main shut off valve check out this post.
2. Turn off the Water Heater.
Water inside the water heater is always at a high temperature and therefore unsafe to work with. This is why you should turn off the gas supply or the heater’s circuit breaker so that the water can first cool off.
If you have an electric water heater, look for the breaker labelled “Water Heater” or “WH” and flip it to the off position.
Also, since you will be draining the tank, you cannot have the element on in an empty tank. It will burn resulting in expensive replacements and other inconveniences.
Note: You do not need to wait for the water to cool off but it is usually recommended. If time is not on your side, turn on one hot water faucet then turn on the water heater’s cold water supply valve for about 5 minutes then turn it back off.
3. Drain the Tank
Since the TPR valve is usually located near the top of the water heater, you do not need to drain the entire tank. Just drain out water until the water level is just below the valve.
Note: Some water heaters have the TPR valve on the side of the tank near the top while others have it at the top.
There are several ways to drain the water heater:
- You can turn on the nearest hot water faucet until you have drained out about 2 gallons of water.
- Connect a garden hose at the water heater drain valve and drain out the same amount of water.
- Drain out the water through the TPR valve itself. You will need a bucket for this.
Draining water out of the tank also helps to release the pressure inside the tank making it safe to work on.
4. Remove the Old Valve
Water heater temperature and relief valves have a vertical discharge pipe connected to them. Do you know why you must always have the discharge pipe on and never capped?
The discharge pipe channels the water being discharged by the valve safely downwards instead of it gushing out straight into your face (if you are there). Discharge pipes also prevent flooding of the basement (or wherever you have the water heater).
That is the main reason why you always have a pan or bucket at the bottom of the discharge pipe. In some houses, the discharge pipe discharges outside the house.
Before removing the valve, start by unscrewing the discharge pipe by turning it counterclockwise. You will need a wrench here.
After removing the discharge pipe, grab the valve with the wrench and turn it counterclockwise to loosen it. Once loose, simply remove it with your hand slowly just in case you didn’t drain out enough water.
Sometimes the valve is just so corroded that it will simply not come off. What you can do in that case is to spray it with WD-40 or a penetrating fluid and after 15 minutes try to break the connection again.
5. Buy the Right Valve
All TPR valves are not the same. That is why you will notice that your old valve has a tag. That tag contains the specifications needed for your water heater.
Use those specifications to buy another valve. You can purchase a new valve online or you can take your old valve with you to a home improvement store and buy and exact replacement.
6. Install the New Valve
The first thing you will need to do is clean the threads in the water heater valve opening. Use a small wire brush to remove pipe corrosions and old Teflon tape from the threads.
An old toothbrush also works very well here. Clean the threads until they are spotless. That will allow the new valve to seal properly with no potential damage to the threads and hence ensuring there are no leaks.
The next step is to wrap Teflon tape on the valve’s threads. Teflon tape is purely to prevent leaks since it is a thread sealant.
Apply about 4 wraps of Teflon tape nice overwrapped in a clockwise direction from back to the front of the threads. It is important to know how to apply Teflon tape lest you end up with leaks. Check out this post on how to properly apply Teflon tape.
Thread in the new valve slowly to prevent cross-threading until the valve is hand-tight. Use the wrench to tighten the valve. It is important to make sure that the valve is tight but in a vertical direction so that you can connect the discharge pipe.
Connect the discharge pipe to the valve and gently tighten it. Don’t forget to apply Teflon tape here as well.
7. Finish Up
Turn on the water heater’s cold water shut off valve and also turn on the nearest hot water faucet. The reason for turning on the hot water faucet is to bleed off the air in the water heater and thus prevent air lock inside the pipes.
At first, water will be spluttering out of the faucet as the air is released but when the air has been completely bled off a constant stream of water will be observed. At that point turn off the faucet.
Turn on the water heater as well. The process here will depend on whether you have a natural gas or an electric water heater.
Do You Need a Water Heater Expansion Tank?
A water heater expansion tank, also known as a thermal expansion tank is a small tank (about 2 gallons) that is installed between the water heater tank and the cold water shut off valve to prevent your TPR valve from constantly leaking.
If your house has a closed-loop water supply system, you definitely need a water heater expansion tank. A closed-loop simply means that water in your house can only flow in one direction.
That is made possible by the installation of a check valve. A check valve is installed to prevent contaminated water in your house from flowing back to the city’s water supply and contaminating it as well.
If you have a pressure reducing valve in your home then it also acts as a check valve. A hot water recirculation system also must have a check valve to prevent the cold and hot water from mixing.
Without a check valve, if the water in your water heater expands (due to high pressure and temperature), it will simply flow back to the water supply pipe hence making the system safe.
However, if you have a check valve there is no way water can flow back to the supply pipe. The excess water will be forced out through the TPR valve. That could be why your valve is always leaking.
A thermal expansion tank has a bladder filled with cold water and an air chamber with same pressure as that of the incoming water. If the temperature and pressure of the water heater increases, the excess water is forced to the thermal expansion tank.
The excess water compresses the air chamber at the top making the water heater safe again.
If you have a water heater expansion tank but still your water heater relief valve is always leaking, the expansion tank could be waterlogged. This happens when the bladder bursts meaning there is no more air chamber to compress.
A waterlogged thermal expansion tank will need to be replaced. That should be done by a licensed plumber though.
And basically that is how to replace a water heater temperature and pressure relief valve. I hope this guide was helpful.