Installing a Water Hammer Arrestor: Dos and Don'ts
A loud knocking noise that occurs just after a faucet is turned off is known as a water hammer, and can be fixed by installing a water hammer arrestor. Installing this device is simple, but here is a list of do’s and don’ts that will ensure that the project goes as smoothly as possible.
Like any other plumbing project, begin by shutting off the water. Next, cut a section in the piping as close as possible to either the water intake valve or faucet. Be sure that the cut section is large enough to accept a tee fitting.
Do not glue or solder the tee into place until all the water has drained from the cut pipe. To ensure that the pipe is completely dry, place a small piece of white bread in the cut portion of the pipe to absorb the excess water droplets. This bread will eventually disintegrate and flush through the system.
Once the tee is installed, glue or solder a nipple to the top part of the tee. After the nipple is secured to the tee, connect a reducing female adapter to it.
Do not use any pipe fittings that are not made of the same material as the pipe. For instance, if there is copper piping below the sink, do not try to connect a PVC tee fitting to it. If the fittings are not made of the same material as the piping, the bond between the two will not be as strong as it should be. This is because the pieces will not be able to be secured properly (ie. PVC cannot be soldered and glue won’t bond well to copper).
Screw the water hammer arrestor into the female reducer and tighten it down with a wrench.
If a rattling in the pipes continues to be heard even after the water hammer arrestor is installed, do not automatically assume that the arrestor is defective or that it was installed wrong. Water hammers, over time, can loosen pipes from their supports. So even if the arrestor is working, the flow of water running through the loose pipes can cause them to bang against the wall and produce a rattling noise. Check to make sure that the pipes are secure before seeking professional assistance.