Vent, Valve & Volt
Pipes banging in the walls

This one needs a licensed pro

Call a plumber: noise with no water running

Water hammer happens when a valve closes. A knock, tick or hiss with every tap off needs a plumber to look at it.

Why this happens

Sioux Chief and Family Handyman both describe water hammer as the shock that follows a sudden stop of flowing water, so a noise that goes on with everything off points to something else. A. O. Smith lists hissing among water heater sounds. EPA says that if a water meter changes at all over two hours when no water is being used, you probably have a leak.

What to do right now

  1. If you smell gas at any time, leave the house and call 911 and your gas utility from outside.
  2. The Pennsylvania PUC says not to turn lights on or off or make calls from inside.
  3. Atmos Energy says not to rely on your sense of smell alone, and to use sight and hearing too. If the hissing comes from near a gas pipe or a gas appliance, treat it as a possible gas leak: leave the house and call 911 and your gas utility from outside.
  4. Make sure every tap and every water-using appliance is off. If the sound is coming from the water heater, do not open its panels and call a licensed plumber. If water is coming from the relief valve pipe, keep people and pets away from the end of that pipe.
  5. Check your water meter, as EPA describes: read it, wait two hours with no water used, and read it again. If it moved at all, you probably have a leak.
  6. If the meter moved, shut off the main water valve by hand and call a licensed plumber. Bob Vila says a ball valve, which has a lever handle, turns clockwise 90 degrees, and a gate valve, which has a round handle, takes a few turns clockwise until it stops. Never force the valve. If it will not turn, call a plumber and your water utility. If it did not move, still call a plumber to find the source of the noise.

When to stop. A wet spot, a stain, dripping, or the sound of running water with every tap off means shut off the main by hand and call a plumber now. Never force a stuck valve. A gas smell means leave and call from outside.

What to tell the plumber

  • What the noise sounds like and where in the house it is loudest.
  • Whether the water meter moved during the two-hour check.
  • When it started and whether anything changed just before, such as plumbing work.

Build the full list: what to tell the plumber.

Start this troubleshooter over

References (every fact above comes from one of these pages)
  1. Sioux Chief: Water hammer control engineer report (manufacturer document, copy hosted by InspectAPedia)
  2. Family Handyman: Water pipes making a banging noise
  3. A. O. Smith: Hot water heater making noises
  4. EPA WaterSense: Fix a Leak Week
  5. Bob Vila: How to turn off water to your house
  6. Pennsylvania PUC: Gas emergencies
  7. Atmos Energy: Recognizing a leak

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