Rheem T&P Relief Valve — Test, Replace, Troubleshoot

The T&P (temperature and pressure relief) valve is the most important safety device on any Rheem tank water heater. It opens automatically if the tank exceeds 210°F or 150 psi, preventing the tank from rupturing or — worst case — exploding catastrophically. The valve is cheap (~$25) but absolutely critical, and most homeowners never test it.

How to test the T&P valve — annually

1. Locate the T&P valve — top or side of the tank, with a metal flip-lever and a copper or PVC discharge tube routing to a floor drain or outside
2. Place a bucket under the discharge tube outlet
3. Flip the lever fully open for 1–2 seconds — water should rush out the discharge tube
4. Release the lever — water flow should stop completely within a few seconds
5. If water continues to drip after release, the valve seat is fouled — try again. If still dripping after 3 attempts, replace the valve.

This test should be done annually. If you've never done it, do it now.

Why T&P valves fail

T&P valves are mostly mechanical — a spring loaded against a brass seat. Failure modes:

• Mineral buildup on the seat — won't fully reseat after flipping, dribbles continuously
• Spring fatigue after 5–10 years
• Corrosion of the brass seat in aggressive water
• Stuck closed — most dangerous failure; valve won't open even when needed

Replace the T&P every 5 years as preventive maintenance. The valve is $25 and the alternative outcome (tank rupture) is catastrophic.

Continuously dripping T&P — what it means

If you find your T&P discharge tube wet during normal operation (not just after testing):

1. Check incoming water pressure with a gauge at any outside hose bib. If above 80 psi, install a pressure-reducing valve at the main supply. Excess pressure forces the T&P open intermittently.
2. Check the thermal expansion tank — closed-system plumbing (with a backflow preventer at the main) needs a thermal expansion tank. Without one, water heated in the tank has nowhere to go and pressure spikes, opening the T&P. Install the expansion tank (~$50) above the cold-inlet line.
3. If neither pressure nor expansion is the issue, the T&P seat is fouled — replace the valve.

T&P valve replacement

Rheem T&P valves are universally compatible — Watts 100XL or M&M T&P, 3/4" MIP, 150 psi 210°F rating. $20–$30 at any plumbing supplier.

Replacement procedure

1. Shut off power/gas and cold-water inlet
2. Open a hot-water faucet to relieve pressure
3. Drain ~2 gallons from the tank to drop water level below the T&P location
4. Unscrew the discharge tube from the existing T&P
5. Unscrew the T&P valve from the tank port (counter-clockwise) with a pipe wrench
6. Wrap the new T&P threads in Teflon tape
7. Hand-thread the new T&P, then snug with a wrench (hand-tight + 1 turn)
8. Reattach the discharge tube — must route downward, terminate within 6" of the floor or to a floor drain (most local codes)
9. Restore inlet water, refill, restore power/gas
10. Test the new valve to confirm it operates

Bottom line

The T&P valve is $25 and prevents catastrophic tank rupture. Test annually, replace every 5 years. If it drips continuously, the underlying issue is water pressure or thermal expansion — don't cap or plug the T&P, that creates the exact safety hazard it's designed to prevent. For full Rheem parts directory see our Rheem parts hub.