What the valve is telling you
Every tank water heater has a temperature and pressure relief valve near the top, with a discharge pipe running down the side or out through a wall. It opens if the tank gets too hot or the pressure inside gets too high, preventing a dangerous failure.
Occasional drips after the heater runs often point to thermal expansion in a closed system, especially where a pressure regulator stops expanding water from moving back to the street. Constant dripping can mean house pressure is too high overall, the valve itself is worn or scaled, or the heater is overheating.
Matching the drip to a cause
- IfDrips mostly after showers or laundryThenThermal expansion; check for a working expansion tank.
- IfDrips constantly and the house gauge reads highThenIncoming pressure or a failing regulator.
- IfDrips with normal pressure and a good expansion tankThenThe valve may be worn or scaled and need replacing.
- IfWater is very hot at taps and the valve releasesThenPossible thermostat or control problem; stop using the heater and call a plumber.
How a plumber usually sorts it out
- Read the pressure.A gauge on a hose bib or at the heater's drain shows house pressure, including how it changes after heating.
- Check the expansion tank.Confirm a tank exists, is not waterlogged and has the right pre-charge.
- Inspect the valve and discharge line.Look for scale, damage and a discharge pipe that terminates where it should.
- Check temperature controls.Make sure the heater is not overheating.
- Fix the cause, then the valve.Replacing only the valve without fixing pressure usually means it will drip again.
While the heater is being looked at
What affects the scope
| Situation | Likely work |
|---|---|
| Worn valve only | Valve replacement |
| Thermal expansion | Expansion tank added or replaced |
| High incoming pressure | Regulator service or replacement, then retest |
| Aging tank with multiple issues | Discussion of repair versus heater replacement |
| Missing or loose strapping | Strapping corrected; permit questions for heater work go to the City of Fullerton |
Common questions
Can I test the relief valve myself?
Manufacturers describe a test in the heater's manual, but an old valve may not reseat afterward and start dripping. If you are unsure, let a plumber do it.
Where should the discharge pipe end?
It should terminate in a safe, approved location. A plumber can tell you whether yours meets current requirements.
Does a tankless heater have a relief valve?
Most do. The same rules apply: do not block it, and have discharge investigated.
General information for Coyote Hills, not a quote or professional advice. In an emergency, call 911.