My wife was home today during a follow-up visit from the sump pump replacement we had as a result of my sump pump issue. After solving the problem, the plumber opened a the release valve from the water heater to drain into the pit, in order to test. Once it shut, it began dripping at a medium pace (not a slow drip that has to build up, but nothing even near a trickle). My wife tells me that the plumber attempted briefly attempted to hammer it fully closed. She thought the dripping would stop, but now, 4 hours later, it is still dripping. The heater has never dripped before.

Is the dripping something we should worry about? Will it eventually stop on its own? Will it cause problems?

  • Resolution: Answers seemed to indicate that this was a problem likely to occur with old/rusty water heaters. Mine is neither. In the end, I used a board to press firmly against the pin that acts as a stopper for the release valve (the same thing the plumber had hammered against). By applying even, firm pressure instead of whacking it, the dripping stopped. Dec 18, 2010 at 15:41
  • 1
    make sure that the valve still opens and closes properly, as it's a safety feature of the heater.
    – Niall C.
    Dec 18, 2010 at 16:04

2 Answers 2


Niall is correct. Opening the T&P valve to drain water from the water heater is a common practice, but if it's really old, it can be damaged by sediment and corrosion. Where the plumber went wrong is not using the T&P valve to drain some water, but rather trying to hammer it shut. T&P valves prevent BLEVEs (Boiling Liquid Expanding Vapor Explosion), which are a type of catastrophic explosion -- in this case, in the event of a malfunction in the water heater. Let's just say that if your water heater BLEVEs, you can kiss your entire house goodbye, so since there is clearly a problem with your T&P valve, you need to get yourself a new one.

In order to replace the T&P valve, you can call a plumber or do the following:

1) Turn off the cold water ball valve. 2) TURN OFF THE WATER HEATER'S BREAKER IN YOUR BREAKER BOX (if the top heating element hits air, you can damage it, and it will make a massive shotgun-like sound) 3) Open some hot water outlets, such as the hot water handles on a few sinks. These will allow air into the top of the hot water heater. 4) Run a garden hose from the hot water heater's drain to the street/driveway. 5) Open the water heater's drain, and empty the hot water heater below the T&P valve. 6) If it does not flow on its own, you have sediment build-up (which you most likely do if your T&P is failing.) If it doesn't flow, open the cold water ball valve so that the water pressure can help break through the sediment layer. After 2-3 minutes, close the cold water ball valve again to allow the top of the water heater to fill up with air. 7) Replace the T&P valve. Use teflon tape to help create a seal.

8) Turn off the drain. 9) Remove the garden hose, but keep it held high so no water comes out the end that is in your hand... and take it back outside. 10) Open the cold water ball valve. 11) A mixture of water/air should come out of the still-opened sinks after 1-2 minutes. You can shut them off at this point if you don't mind seeing the air bubbles the next time you use the sink. 12) Turn the water heater's breaker back on.

  • 2
    If you DO call a plumber, call a better one than the first one who caused this problem, and then failed to repair it.
    – user558
    Dec 19, 2010 at 18:33

It shouldn't be dripping at all. If you're interested, try catching the water in a container for a time and do some multiplying out to see how much hot water is being wasted. In my answer to Is flushing a waterheater a good idea?, I gave an estimate of how much it costs to flush and reheat a full tank. From there, you could extrapolate to see how much it will cost you if you don't get it fixed.

I doubt that it would stop on its own: any water heater is going to build up mineral deposits, especially so in a hard water area. I suspect some became lodged inside the valve when the plumber opened it. You might be able to get it to stop by opening it again and letting some more water flush through it, which might dislodge anything that got stuck in there. If that doesn't work, you might have to replace the valve: here are some instructions on how to do that.

  • @ Niall. Since the cold water inlet should have a dip tube, you do not actually waste much hot water if you keep the cold water inlet open (since the hot water will stay near the top and the water going out, after 30 seconds or so, will be cold)... or if you only partially drain the water heater. In reality, draining sediment is actually cheaper than your calculation!
    – Michael
    Dec 19, 2010 at 4:25

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.