Bradford White Water Heater T&P Valve Replacement Guide — What This Part Does
The temperature and pressure relief valve (T&P or TPR) is a mechanical safety device that opens to discharge water if tank temperature exceeds 210°F or pressure exceeds 150 psi. When the valve senses unsafe conditions, it lifts to release pressure and prevent tank rupture. Over time the valve can fail to reseat after a test, wear out from repeated cycling, or collect sediment on the seat that prevents a tight seal.
A leaking T&P valve does not automatically mean your tank is bad. Nuisance discharge is often caused by thermal expansion in a closed plumbing system where check valves, backflow preventers, or pressure-reducing valves trap expanding water and push system pressure high enough to crack the T&P open. Replacing the valve and addressing the root cause (usually adding a thermal expansion tank) stops the drip and keeps the heater safe.
Signs It Needs Replacing
- Constant drip from the discharge tube Water drips continuously from the TPR discharge pipe even when the heater is cold or idle.
- Discharge only during heating cycles The valve releases water each time the burner fires and the tank heats up, indicating thermal expansion pressure.
- Valve will not reseat after test After you lift the test lever the valve continues to leak instead of closing tight.
- Visible corrosion or mineral crust on the valve body White or green deposits around the valve threads or outlet show long-term weeping and corrosion.
- Water pooling under the heater A puddle forms beneath the tank with no other obvious leak source, and the discharge tube is wet.
- Hissing or steam from the relief valve You hear a hiss or see steam escaping from the valve during operation, signaling a pressure or temperature event.
How to Replace It
- Turn the gas control knob to pilot (or off if no pilot) and shut off the cold-water supply valve at the top of the heater.
- Connect a garden hose to the drain valve at the base of the tank and run it to a floor drain or outside.
- Open the drain valve and a hot faucet upstairs to introduce air, then drain the tank down below the level of the T&P valve on the side of the tank.
- Unscrew the discharge pipe from the outlet of the old T&P valve and set it aside, then use a pipe wrench to turn the valve body counterclockwise out of the tank opening.
- Inspect the new valve to confirm it matches the old valve’s temperature rating (typically 210°F), pressure rating (150 psi), and BTU capacity stamped on the body (part 415-32920-01 is a common 3/4 x 4 inch valve, and part 415-40594-02 is rated for 105,000 BTU/hr on certain models).
- Wrap the male threads of the new valve with three to four turns of approved Teflon tape (not pipe dope on potable water fittings unless specified), then thread the valve into the tank opening hand-tight.
- Tighten the valve with a wrench until snug, making sure the discharge outlet points straight down and the test lever is accessible.
- Reconnect the discharge pipe to the valve outlet so it terminates within 6 inches of the floor or routes to an approved drain, with no threads or cap on the end.
- Close the drain valve, remove the hose, then slowly open the cold-water supply and let a hot faucet run until water flows steadily with no air sputter.
- Check all connections for leaks, then turn the gas control back to the desired temperature setting and relight the pilot if required.
- If the valve was leaking due to thermal expansion, install a properly sized domestic thermal expansion tank on the cold-water line to prevent future nuisance discharge.
The Part You Need
| Part | Notes |
|---|---|
| Bradford White T&P relief valve | Amazon | Match the temperature, pressure, and BTU rating stamped on your existing valve. Common OEM numbers are 415-32920-01 (3/4 x 4 inch) and 415-40594-02 (3/4 inch male, 105,000 BTU/hr). Check the model and serial plate on the front of your heater for exact specifications. |
| Teflon tape or approved thread sealant | Amazon | Use only tape or sealant rated for potable water connections on the valve threads. |
| Thermal expansion tank (if needed) | Amazon | Required when your plumbing has check valves, backflow devices, or pressure-reducing valves that create a closed system and cause the T&P to drip from thermal expansion. |
When to Call a Pro
If you are uncomfortable draining the tank, working with gas controls, or diagnosing whether a closed plumbing system is causing the problem, call a licensed plumber or water heater technician. A pro can pressure-test your system, size and install a thermal expansion tank if required, and confirm that the new valve is installed to local code. If the valve continues to discharge after replacement and expansion-tank installation, the tank itself may have sediment buildup or internal scale that requires professional flushing or replacement. For gas line, burner, or igniter work, or if you ever smell gas, stop and call a licensed technician.