# Water heater relief valve leaking or dripping: what to do

Updated: 2026-10-24 · https://pros411.com/en/guides/plumbers/water-heater-relief-valve-leaking

## Short answer

Never cap or plug a dripping relief valve: it is the safety valve that keeps the tank from bursting. If it lets out a steady stream or steam, turn the heater off (gas knob to OFF or the breaker) and call a plumber now. A small drip often means the water pressure is too high or the valve is worn. A plumber can test the pressure, add an expansion tank or replace the valve.

> Safety first: Water and steam from the relief valve can scald: keep hands and faces away from the end of the pipe. Never cap, plug or shorten the discharge pipe, and do not lift the valve lever on a hot tank. Smell gas? Get out and call 911 or the gas company from outside.

## What to do when the water heater relief valve drips

![Cartoon water heater with its relief valve pipe dripping into a puddle while a cat watches](https://pros411.com/img/guias/water-heater-relief-valve-leaking.webp)

1. **Water dripping from the side pipe.** The pipe that runs down the side of the tank comes from the relief valve. It opens when the tank gets too hot or the pressure gets too high.
2. **Never cap or plug it.** That valve keeps the tank from bursting. Put a bucket under the pipe instead and keep kids and pets away from it.
3. **Steam or a steady stream? Off and call now.** Turn the gas knob to OFF, or switch off the breaker on an electric heater. Then call a plumber right away. Do not wait for it to stop.
4. **Too much pressure is a common cause.** A plumber can screw a gauge onto the drain valve or an outdoor faucet. Above about 80 psi, the pressure in the house is too high.
5. **An expansion tank or a new valve fixes it.** Heated water expands. A small expansion tank on the cold pipe gives it room. If the valve itself is worn, the plumber replaces it.

## Why it drips

- High water pressure coming from the street.
- Thermal expansion: heated water has nowhere to go when the house has a pressure regulator or a check valve and no expansion tank.
- The water is too hot. Check that the dial on the gas control is not on its hottest setting.
- A worn valve that no longer seals, often after years of use.

## What not to do

- Do not cap, plug or tie off the discharge pipe. That turns off the safety valve.
- Do not lift the test lever on a hot tank. It can spray scalding water and may not seal again.
- Do not swap in a valve with a different rating. A plumber matches it to the heater.

## When to call a plumber

- Water or steam keeps coming out of the relief valve pipe.
- The tank or the pipes on top are very hot, or you hear hissing or banging.
- The drip came back after a new valve was installed.
- Your water pressure tests above 80 psi.
- Any gas smell (call 911 or the gas company first, from outside).

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## Frequently asked questions

### Is it normal for a water heater relief valve to drip?

No. A drip means the tank is too hot, the pressure is too high or the valve is worn. A small drip is not an emergency, but call a plumber soon.

### Is a leaking relief valve dangerous?

A steady stream or steam is: turn off the heater and call a plumber now. The bigger danger is capping the valve, because then nothing protects the tank from bursting.

### Can I replace a water heater relief valve myself?

It is a job for a plumber. The tank has to be cooled and partly drained, and the new valve has to match the rating of the heater.

### What causes too much pressure in a water heater?

Usually high street pressure or thermal expansion: heated water grows and has nowhere to go. An expansion tank or a pressure reducing valve fixes it.

### Should water ever come out of the relief valve pipe?

Only when the valve releases dangerous heat or pressure, or during a test by a pro. Water coming out on its own means something needs to be checked.