If the temperature and pressure relief valve on your water heater drips, drains, or leaks in a Washington home, the valve is doing its job by releasing pressure. It is also telling you something about the system. Treat a dripping valve as a signal to find the cause, not as a leak to ignore or plug.
What the valve is for
The relief valve sits on the side or top of the tank. It opens if the water gets too hot or if tank pressure climbs past its rated limit, and it sends water out through a discharge pipe that runs toward a floor drain or outside. Because it is a safety device, it should never be capped, plugged, or removed.
Common causes
Water expands as it heats. In a home where water can flow in but cannot flow back out, that expansion has nowhere to go, so pressure rises. Several things make this more likely:
- A check valve, backflow preventer, or pressure reducing valve on the main line, which closes the system so expanding water cannot push back toward the street.
- Incoming pressure that runs higher than normal.
- A thermostat set higher than your household needs, which heats the water further than necessary.
- Sediment or mineral scale on the valve seat, which keeps the valve from sealing fully after it closes.
- A failing expansion tank, if your home has one, because a waterlogged tank cannot absorb the extra volume.
Checks to make before anything else
- Look at the discharge pipe. Small amounts of water that appear only while the heater is heating or shortly after point to expansion. Steady flow, or water that runs at all times, is different and needs prompt attention.
- Check the thermostat dial. Lower it to a moderate setting and watch over several heating cycles to see whether the dripping stops, keeping in mind that the setting must still meet your household's hot water needs.
- Look for white or gray crust around the valve and the discharge outlet. Public water reports describe tap water in Washington as very hard, and mineral crust can build up quickly on a valve, sometimes holding it partly open.
- Find the expansion tank if your home has one, usually on the cold water line near the heater. Tap it. A solid sound suggests it is full of water, while a hollow sound suggests it still holds air.
- Note whether any device on the main line closes the system, such as a check valve or backflow preventer, and whether it was installed recently.
Testing the valve safely
Many valves have a test lever. Lifting it briefly should release a short burst of water and then reseat the valve. Hot water can scald, so stand to the side, keep your hands clear of the discharge, and confirm the outlet is piped to a safe place before you test. If the valve does not reseat after the test, or if it keeps dripping afterward, the valve itself may need replacement.
What to leave to a licensed plumber
Call a licensed plumber if the valve discharges steadily, if the discharge pipe is blocked or missing, if you cannot identify any expansion control and the pressure seems high, or if the valve shows visible damage. Replacing a relief valve or changing main line pressure requires a qualified professional. Do not cap the discharge pipe or keep running the heater with a faulty valve.
Water quality and the valve
Hard water is one reason a relief valve may stop sealing well. Scale can collect on the seat and spring, so even a valve in good condition can weep. Clearing the discharge area and confirming how any softener in your Washington home is set up on the main line can help you understand what is happening, but the valve's rating and the system pressure are what decide whether it is safe.