A.O. Smith Water Heater T&P Valve Replacement - Signs & How-To

A.O. Smith Water Heater T&P Valve Replacement — What This Part Does

The Temperature & Pressure Relief (T&P or TPR) valve is a safety device that opens when your water heater exceeds safe temperature or pressure limits. It prevents tank rupture by automatically releasing hot water and steam through a discharge tube when conditions inside the tank become dangerous.

The valve fails when high system pressure forces it to drip continuously, when thermal expansion in a closed plumbing system raises tank pressure beyond its rating, when a malfunctioning thermostat allows overheating, or when the threaded seal at the tank opening deteriorates. A.O. Smith specifically notes that excess pressure (above the 80 psi code maximum) and thermal expansion on closed systems are the most common causes of valve seepage, and recommends installing a thermal expansion tank and correcting system pressure before simply replacing a dripping valve.

Jump to Replacement Steps

Signs It Needs Replacing

• Hot water discharging from the relief valve or drip tube The valve opens intermittently and releases hot water through the discharge line, usually indicating overheating from a bad thermostat or excessive system pressure.
• Continuous dripping or seepage from the valve body Water drips steadily from the valve itself, often caused by high water pressure or thermal expansion forcing the valve to weep.
• Leak at the threaded tank connection Water seeps from where the valve screws into the tank, indicating the thread seal has failed and needs resealing or valve replacement.
• Water pooling near the top or side of the heater Moisture collects around the T&P valve area, which can come from the valve, the threads, or the tank spud itself.
• Valve opens during heating cycles The relief valve discharges only when the burner or elements are heating water, pointing to thermal expansion problems in a closed plumbing system.
• Seepage at the welded tank spud area Water leaks from the welded connection where the valve mounts to the tank, which A.O. Smith states is not repairable and means the entire water heater should be replaced.

How to Replace It

1. Turn off the energy source: flip the circuit breaker off for electric models or turn the gas control to Off and extinguish the pilot for gas units.
2. Shut off the cold water supply valve at the top of the water heater.
3. Open a hot water faucet somewhere in the house to relieve pressure in the system.
4. Attach a garden hose to the drain valve at the bottom of the tank and drain enough water so the level drops below the T&P valve opening on the side or top of the tank.
5. Disconnect and remove the discharge tube or pipe from the old T&P valve.
6. Use a wrench to unthread and remove the old relief valve from the tank opening.
7. Wrap the threads of the new T&P valve with Teflon tape or apply pipe thread sealant as directed, then thread the new valve into the tank opening and tighten with a wrench.
8. Reinstall the discharge tube to the new valve outlet, applying thread sealant where required, and make sure the tubing is at least 3/4 inch inside diameter and slopes downward for proper drainage per A.O. Smith specifications.
9. Close the drain valve, reopen the cold water supply, and let the tank refill completely.
10. Run a hot water faucet for 3 minutes to purge air from the tank and system.
11. Restore power by turning the breaker back on or relighting the pilot and turning gas back on, then check all valve connections and joints for leaks after the system is pressurized and heating.

The Part You Need

Related Error Codes

If this part is failing you may also see one of these codes:

• A O Smith Water Heater E2 error code
• A O Smith Water Heater E4 error code
• A O Smith Water Heater E6 error code

When to Call a Pro

If the leak is coming from the welded tank spud where the valve mounts to the tank, A.O. Smith says this connection cannot be repaired and the entire water heater must be replaced. Call a licensed plumber for tank replacement, for installation of a thermal expansion tank or pressure-reducing valve to correct the root cause of valve discharge, or if you have a gas water heater and are not comfortable working with gas lines and pilot lights. If your system water pressure exceeds 80 psi or you have a closed plumbing system causing thermal expansion, a professional should diagnose and install the necessary expansion tank or pressure controls before you replace the valve, or the new valve will fail the same way. For gas line, burner, or igniter work, or if you ever smell gas, stop and call a licensed technician.