I have a tap dripping hot water and need to turn off the supply of hot water. The house has a gas water heater in the basement. There is a valve on the water supply leading into the tank and another valve on the hot pipe coming out of the tank. To work on my dripping hot tap, is it better to turn off the water going into the tank, the water coming out, or both?


  • 2
    Usually there's a shutoff under the sink where the tap is located. Have you checked?
    – HoneyDo
    Aug 13, 2021 at 19:21
  • 1
    If no shutoff under the sink, then output valve on tank, since tank has usually a bit of pressure above inlet pressure.
    – crip659
    Aug 13, 2021 at 19:28
  • It's a tub tap, so no, no shutoff. I appreciate the tips to use the output valve.
    – Robert
    Aug 14, 2021 at 1:48
  • 1
    Also flip the gas control valve to "pilot" if shutting off the water. And consider adding a shutoff for the tub tap (might be accessible via an access panel in another room, or in the basement or the ceiling of the floor below, depending on pipe layout and where the tub is located in the house.)
    – Ecnerwal
    Aug 14, 2021 at 17:42
  • I hope that, while you had the water off to fix/replace the tub tap, you added a conveniently located shut off just for the tub! Makes life much easier the next time you (or someone) has to do some work there.
    – FreeMan
    Sep 13, 2021 at 16:45

1 Answer 1


AFIK the code only requires a shutoff valve on the inlet side of a tank water heater so most don't have one on the outlet. When we had tanks I would always shut the inlet side. But if you have one on the outlet you could use either one. I would not shut off both at the same time.

  • Just curious: what's the reasoning behind not shutting both?
    – Robert
    Aug 14, 2021 at 1:59
  • 1
    I am perhaps behind the times thinking that trapping the water in the heater with inlet and outlet valves shut could cause the pressure to rise if the heater would come on. Or if the temp of the water went lower the volume of the trapped water would decrease and the pressure would drop. Aug 14, 2021 at 3:05
  • That makes sense. Thank you.
    – Robert
    Aug 14, 2021 at 3:10

Your Answer

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

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