Repair when Refilling

How to fix water hammer or resonance causing loud noise

Read below for information on how to fix:

1. WATER HAMMER: A loud bang in your pipes after a fill valve shuts off. Water hammer can be caused by worn or damaged faucet washers as well as heavy build up of minerals and rust inside shut off valves (located on the walls of your home).

2. RESONANCE: The rapid banging or “Jack Hammering” sound in a pipe during the fill process, during the flush.

Follow these steps to try and resolve water hammer:

  1. Shut off water supply to the house at the main.
  2. Open all the cold water faucets, start with the highest faucet (2nd or 3rd floor) and work to your lowest faucet (first or basement floor).
  3. Flush all the toilets in the home.
  4. Let water drain from open faucets. Wait approximately 20 to 30 minutes.
  5. Turn on water supply to the house at the main.
  6. Wait 5 to 10 minutes to let faucets regain a strong stream and flow water.
  7. Close all the cold-water faucets starting with the lowest faucet (first or basement floor) and to the highest faucet (2nd or 3rd floor).
  8. Toilets will automatically refill.
  9. Once all faucets are closed and toilets filled, flush toilets to check for water hammer.

If this does not resolve your issue, try these tips:

  1. Reduce flow from shut off valves (wall or floor valves).
  2. If you are not using a regulated fill valve (a toilet valve that regulates flow into the toilet tank), try replacing the toilet fill valve with a Fluidmaster PerforMAX® Fill Valve.
  3. If reduction of shut off valve does not resolve issue, Fluidmaster recommends calling a plumbing professional to help resolve the issue.

If you need to replace any of the toilet parts, why not get Fluidmaster’s Everything Kit includes everything you need to fix your toilet in one purchase?

If you have a 2″ flush valve, we recommend the 2″ Everything Kit

If you have a 3″ flush valve, we recommend the 3″ Everything Kit


Follow these steps to try and resolve resonant noise (resonance) or watch this video:

    1. Turn off water supply and flush the tank.
    2. Reach inside the tank with your right hand under the float cup and lift it up. With your right hand hold onto the gray shaft keeping the float cup all the way up. Do not allow the float cup to drop or valve shaft to turn.
    3. Place your left hand on the top of the valve cap and while placing your left hand thumb on the side of the arm coming out of the top. Turn the cap and lever counter clockwise 1/8th of a turn to unlock. You should be able to lift off the cap and lever from the valve body.
    4. Once the cap assembly has been removed inspect for debris on the seal (rubber disc with pin coming through) and also the valve portion still in the tank.
    5. Hold a cup upside down over the exposed opening of the valve and turn on the water supply full force for 10-15 seconds, allowing the pressure to free any debris inside the valve inlet.
    6. Reassemble the top of the valve by placing the cap arm next to the refill tube. To lock, press the cap down while turning it and the arm clockwise.


The bottom hand is lifting up on the float cup which raises the black arm under the top cap. The top hand is gripping the cap while the thumb is pressing on the raised lever arm.

If cleaning out the water system does not resolve issue Fluidmaster recommends calling a plumbing professional to help resolve the issue.