Fix a Dripping Water Heater Relief Valve — Exercise It First, Replace It Only If That Fails

The Problem

A dripping temperature and pressure (T&P) relief valve on a water heater doesn't always mean replacement — but on an older tank, sediment can build up inside the valve until it seizes completely, and at that point nothing short of a full swap fixes it.

The Technique

Step one: try to exercise the valve.

1. Put a bucket under the valve's discharge and pull the test lever.
2. If water flows and the valve reseats cleanly with no drip, the problem may already be solved.
3. If nothing flows at all when you pull the lever, sediment has seized the valve internally — that's your sign to move to step two.

Step two: replace the valve.

1. Shut off the water heater's cold supply, and drain at least 10 gallons from the tank through the drain valve — enough to drop the water level below the T&P valve's port. Loosening a fitting on the hot side lets air into the tank so it drains.
2. With the water below the port, remove the old valve. On an older tank, sediment buildup can make this stubborn — a larger wrench may be needed to break it loose.
3. Clean any sediment out of the port threads before installing the new valve.
4. Match the new valve's shank length to the old one, wrap the threads with Teflon tape, and thread it in. The outlet must point straight down — snug it down but don't overtighten past that position, or you risk damaging the port.
5. Exercise the new valve once installed: pull the lever, confirm water flows and the valve reseats with no leak.
6. Restore water pressure, then run hot water at each fixture to flush air out of the lines. Check the whole system for leaks, not just the valve itself.