What is a TPR Valve?
The Temperature Pressure Relief valve (TPR valve) is a safety feature that all water heater tanks should have. The TPR valve has two purposes; to protect the water heater from overheating and over-pressurizing. It accomplishes this by:
- Releasing the water if it gets above 210 F.
- Relieving the pressure inside the tank if the pressure increases above 150 psi.
Releasing water that is higher than 210 F, prevents the homeowner, family, and guests from getting scalded at the sink faucet and shower heads. This is most important when children and elderly live on the property.
Relieving the pressure prevents the tank from rupturing and creating a water leak, which can be very costly depending on the location of the water heater. With a ruptured tank, the owner will need to replace the water heater and potentially make repairs to walls and floors.
Components of a TPR Valve
There are two main components to the TPR valve. The valve itself and the discharge pipe for the valve.
- It is very important that there is a discharge pipe. The purpose of the pipe is to guide the steam either to a safe area outside the house or towards the floor. Without the pipe, the valve can open and release the hot steam towards a person passing by causing burns, or towards a wall causing water damage.
- The discharge pipe should never be routed upwards. When the valve opens the water inside the tank gets released as steam, and if the drain pipe is routed upwards, the steam can condense back into liquid water and drip back down towards the valve, causing rust. The rust can prevent the valve from opening the next time it’s needed.
- Neither the TPR valve nor the drain pipe should be plugged or sealed. Closing this path will create the same problems as if there was no TPR valve at all.
The Mythbusters did an excellent job at showing what happens when the TPR valve is not present or capped in this video.
As the homeowner, there is some minor maintenance you should do to the TPR valve. It is important to note that this maintenance should only be done if the discharge pipe is present. The valve should be open every six months to ensure that is working properly.
If the valve does not release steam or water when opened, it should be replaced by a licensed/qualified plumber. If the valve/pipe drips after the valve have been closed, the valve should also be replaced by a licensed/qualified plumber.