How to Fix or Eliminate Noisy Water Pipe Hammering

The phenomenon known as "water-hammering" is a pressure "shock-wave" that occurs in water supply systems whenever there is a sudden change in the flow of water. Faucets, toilets, and solenoid-activated valves found in washing machines and dishwashers are examples of fixtures and appliances that can cause water hammering.

The most common way of protecting pipes and journals from water hammering is to install pipe risers inside the wall at or near each faucet or valve. Risers could be as high as 24 inches or more depending on the pipe diameter. Since most homes have a supply line size of ¾" and a fixture size of ½", the length of these risers could be somewhat less.

The idea is that the risers will trap air within them when the plumbing system is first activated. The column of air in the riser compresses as it absorbs residual shock waves from the sudden change in the water supply flow thereby "softening the blow" to the various pipes and valves.

From time to time, these risers can become filled with water and lose their ability to absorb the shock of the water pressure. When this happens, water hammering may be heard. At this point, the water pipes throughout the system should be drained from the lowest point. This involves shutting off the water main, turning off the electric to the water heater (if an electric water heater is used), and opening all water taps throughout the house including outdoor spigots. If the water heater is to be drained, use caution and follow all manufacturer recommended procedures.

Having accomplished this, shut off all the open faucets and spigots. Restore the main water supply and turn on the faucets at the highest end. This process will restore water into the system, trapping fresh air in the risers.

Other ways of eliminating water hammering are to install low-flow kitchen and bath fixtures along with water saving showerheads and garden hose sprayers. Newer construction and remodeling projects offer opportunities to eliminate water hammering by installing water hammer arrestors rather than in-the-wall risers. Check with your local jobber or professional plumber for your specific water system requirements.

The proper securing of pipes, the installation of low-flow fixtures, the recovery of fresh air in existing risers, and the use of water hammer arrestors are all things you can do to eliminate water hammering in your home.

Remember, always work safely.