Tip & How-To about Heating & Cooling

How to replace a Water Heater Pressure Relief (TP) Valve

A conventional storage water heater has a small valve screwed into its tank that is designed to relieve built-up steam pressure if the water heater overheats--othewise, the pressure could cause the water heater to explode.

This valve has several names, including temperature and pressure relief valve, pressure relief valve, T&P valve, or--in its shortest form--TP valve. As TP valves get old, they can begin to drip or leak and may need to be replaced.
Though it is recommended that you periodically test this device by lifting its little lever to make sure it is working, doing this with an old valve can cause it to leak. With this in mind, be ready to shut off the water supply to the water heater and replace the TP valve if this happens when you test.
Here is how to replace a TP valve:
1. Shut off the cold water and gas or electricity coming to the water heater.
2. Drain the water from the tank until the water level is below the valve. To do this, run hot water at any faucet, shower, or bathtub.
3. Raise the lever on the valve to release any excess pressure. Loosen the valve by turning it counter-clockwise with a wrench, and then remove it slowly. If water begins to pour out, screw it back in and drain more water from the tank. Note: The water may be hot unless you've allowed time for it to cool!
4. Put pipe-thread tape on the threads of the TP valve and then screw it in, turning clockwise. Tighten it with a wrench.
5. Turn the cold water supply and gas or electricity back on and, for a gas water heater, relight the pilot light if necessary.

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how do i install a pressure tank to my water heater?

Do you mean expansion tank? To relieve pressure?
Expansion tank goes on cold water line before cold enters tank.
See image:

Expansion tanks are installed when TP valve is constantly drizzling hot water due to very hot temperature settings. Or when water pressure is high, etc
It's also smart to install expansion tank so plumbing lasts longer, and older tank is less likely to rupture and cause damage. Inspect tank for leaks each 6 months.
Some regions require expansion tank by local code.
Water heater can be damaged when pressure exceeds 80psi. : Test pressure using pressure gauge at water heater drain valve.

Other resources:

Sep 27, 2011 | General Electric Water Heaters

2 Answers

Water is pouring steaming hot water from a copper pipe on the outside of my GSW Series 6 40 gallon water heater onto my basement floor. What is wrong?

Sounds like the TP valve is releasing water.

To protect your property right now, turn off water heater:
Gas: turn gas valve to pilot so pilot light stays lit but burner will not turn on.
Electric: flip circuit breaker off

Next turn off water valve located on cold water line above water heater.
Last, open tub faucet to relieve pressure on tank.
Once pressure is off after a few moments, close tub valve.

The question is why is the TP valve releasing water.

1) Stuck TP valve: raise lever on TP valve and let back down slowly

2) bad TP valve: replace TP using same temp-pressure rating available from hardware store. Wrap teflon tape around threads and screw new TP valve clockwise until very tight. Make sure water is cool before removing valve from water heater. If you take out valve when water heater is hot, it will spew scalding water all over you. This is serious. Let the water cool down for several hours.

3) Runaway heating caused by bad thermostat
Gas: buy replacement valve at Lowes or plumbing store and replace according to instructions.
Electric: several causes. Test parts to determine which needs replacement.

More support:

a) Fixya offers phone support where you speak with a fixya expert on telephone for a fee.
You can use this service if you hit a trouble spot when repairing your tank.

b) You can also call a plumber who will know exactly what to do.

c) You can post questions at a professional plumbing forum:

Dec 20, 2010 | Water Heaters

1 Answer

we have a brand new rheem 40 gal elec water heater, after installation we have water leaking from the base of the relief valve, pooling up in the plastic fitting and making it way over the side all over the floor.

Water heater should be set in a drip pan.
Otherwise, put 1 gallon bucket under TP release pipe to catch water.

When you say relief valve, I assum you are talking about brass valve located on top of tank or near top of tank. This is TP valve and a pipe connects to this valve and runs down to within 6" of bottom of tank. TP valve has a small lever on it.
If you are talking about tank drain valve located at bottom of tank, then add a comment.
Following information is for TP valve.

Dripping TP valve can be caused by 3 different thing:

1) Obstruction inside TP valve. Open TP valve for a moment to flush away particles and slowly lower lever back down. See if water stops dripping, if not, then replace TP valve

2) Defective TP valve: replace TP valve. Turn off electricity to water heater. Let heater cool for several hours so you do not get scalded. Close shut off valve located above tank on cold side. Open tub spout to relieve pressure, open tank drain or open TP valve and empty water below TP valve level. If TP is located on top of tank, not much water has to be drained. Tank is under press when hot, so be careful. Put teflon tape on new valve and install with big pipe wrench by turning clockwise until TP valve is very tight.

3) Overheating tank. TP valve is temperature-pressure valve. If tank water is over 150 degrees, the TP valve starts drizzling hot water to relieve tank pressure.
Lower tank pressure two different ways:
a) turn down thermostat
b) install expansion tank on incoming cold water line

Dec 19, 2010 | Rheem Water Heater Pressure Relief Valve

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