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T&P Relief Valve: How to Replace and Test

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The T&P Relief Valve, short for Temperature & Pressure Relief Valve, is a critical safety device on your water heater. This valve may sit quietly unnoticed on your water heater, but it has a very important purpose: To keep your heater from exploding!

If your T&P relief valve is properly functioning, and your tank has an excess of pressure, the valve will open to relieve the pressure. You may think you have a leaking water heater from the puddle of water on the floor, but it's a sign your valve is working properly. But if your T&P valve is defective, then you need to take action as soon as possible.

What is a T&P Relief Valve?

The T&P relief valve is often located on the side of your tank, but it can also be on the top. There's a long pipe (called a drain or discharge pipe) that's attached to the valve and runs down the side of the heater and ends a few inches above the floor.

T&P valves are required to have a drain pipe, however, on occasion the pipe may not have been installed. If your heater does not have a drain pipe attached, you should hire a plumber or add one yourself.

When the hot water within your tank reaches a temperature of 210°F, or the internal tank pressure exceeds 150 psi (pound per square inch) the T&P valve is designed to open and relieve the pressure within the tank. Once the pressure returns to a safe level, the valve automatically closes.

Checking your T&P valve is one of several preventative maintenance tasks you should perform on a regular basis.

When the T&P Relief Valve Opens

When the T&P valve activates, extremely hot water will be discharged. It's critical from a safety standpoint that the water is delivered to the floor. Without a drain pipe, the discharged water will spray out from the T&P valve and could cause serious injury.

If you notice water around your T&P valve or at the base of the drain pipe there are two possible reasons:

  1. A faulty T&P valve
  2. The T&P valve is properly working and the internal pressure within the tank is too high. 

Either reason requires immediate attention. If the valve is faulty, it needs to be replaced as soon as possible. If the T&P valve is properly working and releasing pressure, then it's critical to determine what caused the valve to trigger.

NEVER cap off the T&P Valve, and NEVER ignore the problem. Your water heater could explode! Read about water heater safety HERE.


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How to Test the T&P Relief Valve

The T&P relief valve should be tested at least once a year to ensure that it's working properly. It's not uncommon for valves to wear out and need to be replaced. 

Always check your owners manual for specific instructions for your water heater. Many manufacturers recommend removing and visually inspecting the valve for signs of corrosion.

Testing a T&P valve:

  • Place a bucket under the T&P drain pipe.
  • Lift the tab on the valve to allow water to flow. The water released will be hot.
  • Close the tab on the valve once the water becomes clear. Usually this takes a few seconds.
  • If the T&P relief valve continues to release water, quickly lift the tab up and down several times to help re-seat the valve.
  • If after attempting to re-seat the valve, the T&P still leaks, the valve needs to be replaced.

Watch the Video

How to Replace a T&P Relief Valve

If you determine that your T&P valve is faulty, then you'll need to replace it as soon as possible. This valve is an important safety device that prevents your water heater from reaching a dangerous internal temperature.

Follow these steps:

  • Turn OFF the power and incoming water to the heater.
  • Drain the water from the tank so that the water level is below the T&P valve. Check this by opening the valve. If water is released, you need to drain more water.
  • OPEN a hot water faucet to allow air to enter the tank. This will assist with draining.
  • Turn the valve counter-clockwise with a wrench.
  • Remove the defective valve.
  • Wrap the threads of the new T&P relief valve with Teflon tape.
  • Insert the new valve into the water heater and turn clockwise until it is firmly locked in place.
  • OPEN the cold water supply to the heater and fill the tank. Do not turn on the power until the tank is full of water.
  • Replace the drain pipe to the T&P valve.
Rheem Temperature and Pressure Relief Valve SP8346, Small

T&P Relief Valve

If your T&P relief valve is defective, it should be replaced as soon as possible.

This video will show you how to replace a T&P valve on an electric water heater.

Watch the Video

T&P Relief Valve Triggering

If the T&P relief valve is not defective, but you're still finding water near the drain pipe, then the valve is functioning properly and performing its intended job.

The T&P valve is opening to relieve pressure from within the tank.

Although you can rest assured that the valve is functioning as it should, there is something wrong with your water heater that's causing the temperature to exceed a safe limit and/or build to an unsafe internal tank pressure.

There are 4 common causes are:

  1. Thermal expansion (when water is heated it expands).
  2. High system pressure.
  3. High temperature relief.
  4. Temperature gauge set too high.

If the problem is the temperature setting is set too high, then the fix is easy. You simply need to turn down the temperature and keep a close eye on your water heater for the next few days to ensure that the T&P valve is no longer discharging water.

However, if this is not your problem, then we highly recommend hiring a professional plumber to investigate the situation and make the repairs. The problem could be serious and it's not worth putting your home and family in danger.


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