What Is a Water Hammer? The Annoying House Sound You Can Eliminate

What is a water hammer? If something goes wrong at night, it could be water flowing through your valves and pipes. However, if you hear loud knocking from your plumbing or valves, it is a problem called water hammer. If your home is more than a decade old, you can probably confirm that you are hearing this sudden and often annoying cacophony. (Light sleepers, you know only too well what we are talking about!) But what is the cause of a water hammer anyway? Our crack plumbing expert will explain everything, including how to stop this crazy water noise from occurring in the first place.

What is water hammer and what causes water hammer problems in pipes?

It is a common misconception that water flows smoothly through pipes, valves, toilets, and the pump. In fact, water swirls and tumbles in your water system as it moves out of a tank, through pipes, and eventually out of valves and taps.

Most of the time, all of this water movement creates a steady sound that we barely notice. But sometimes, if you suddenly turn off the valve or the water, or if the pressure suddenly increases, the water comes to a sharp standstill, causing the familiar water hammer sound. The noise or water hammer is the result of in-line pipes moving and bumping around in their hangers.

Pounding can be caused by soaked air chambers, clogged chambers, or excessive pressure in your plumbing system. It can also be the result of a clogged valve or pipe which can create a staccato popping sound.

You can find this mostly in older homes that says have pipes with 90 degree angles Tom Bigley, United Association plumbing director. “The sound you hear is the pipe moving due to shock waves.”

Newer homes with flexible piping winding through walls rarely suffer from water hammers, Bigley says.

Yes, the pounding is annoying. Worse, a prolonged water hammer sound like this can sometimes cause pipe fittings and valves to fail and pipes to burst. Properly installed pipelines contain air pockets or chambers that compress when a shock wave hits them, dampening the sound of water. But pressurized water absorbs air and eventually erodes the air cushions. Then the problem begins with the water hammer.

How to fix the water hammer yourself

Once you’re feeling at least a little confident (you can locate pipes and valves, and know the difference between an open and a closed valve), here are some quick steps to get rid of water hammer before hiring a professional water hammer trap.

  • If you can hear where the water hammer is coming from e.g. For example, in your bathroom, turn off the water behind the noisy, soaked chamber, turn on the faucet and let the water drain out. When the water speed stops dripping, air will refill the pipes and restore the air cushion.
  • When the water hammer is deep in the pipes, you can turn off the water valve to the house and drain the main water supply lines by turning on all of the faucets in the house, including hose bibs, and letting air flow into the house again pipes. Then close all the taps. Always check the valves – otherwise your pipes will flood the house!
  • Turn the water valve back on. Don’t be alarmed if the pipes spit air the first time you turn on the taps. It is normal after a valve closes.

When to call a plumber about a water hammer problem

If the simple water hammer fixes don’t work, your water lines or valves may be clogged with mineral and general buildup. In this case, you need to throw in the towel (figuratively) and call a plumber.

When the chamber is sealed, the plumber removes the cap and snakes the debris out of the water supply and piping systems. If your system does not have air chambers installed, the installer will attempt to reduce the peak pressure by installing a pressure reducing valve in the supply line (low pressure is usually measured in inches of water). If this is not possible because the water pressure is too low for a good shower and the dishwasher to run or a load of laundry, air chambers must be installed to stop the water hammer. In any case, you should be free of hammer – and sleep well again in no time.

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