I just had my master bathroom and main bathroom completely remodeled. This included all new plumbing from the cold and hot water source downstairs because we also had all the walls open. I now hear a periodic knocking sound when the toilet or main shower is running. Also when you should the water off you hear a taping sound. It is driving me nuts. I do not believe he put in air chambers in the line. The contractor kept teeing off from valve to valve. With out pulling apart my walls is there anyway to fix it? I am sure my contractor will tell me they no longer use air chambers---Can I use mini arresters on the valves? Thanks for your help, Marc

Maybe when the water is on the force of the water makes the pipes knock against the wall
I don't know that was just a guess

Marc, you definitely have an airlock problem in your line. Had your contractor installed a set of 12" air chambers on both ends of your home, this would not have been an issue.

I'm not sure on your arrestor idea. Maybe Tom or one of the other guys can add more on that. If not, it would involve sheetrock removal unfortunately. Hopefully someone else can point you to an easier fix for your air hammer.

Hi Marc,
"The contractor kept teeing off from valve to valve. With out pulling apart my walls is there anyway to fix it? I am sure my contractor will tell me they no longer use air chambers."
Your contractor would be mistaken. It is not good plumbing practice to install a water system without air chambers. Your builder's blowing smoke! Call him back and DEMAND that he do the job right at his expense. More on air chambers below.

"Water hammer" happens when you abruptly shut off the water. You have at least 40 pounds of pressure pushing the water flow. The weight of the water hitting a 90 degree bend causes the sound that you hear. We put in shock absorbers,(air chambers) to cushion the hammer much like the shocks on your car.
Back in the 60's we were required by code to to put shock absorbers,(air chambers) on all bath lavatorys and kitchen sinks. Over time water and condensate built up in them and they must be recharged. First turn off the house at the main house shut off valve. Then open hot and cold faucets at the farthest bathroom to prevent air lock.(This is important.) You will find under each fixture little brass or chrome valves. These are called angle stops. With a small pail held under the angle stop to catch the run off look under the handle of the stop and you will see a nut with the stem running through it. This is called the bonnet packing nut. Put your wrench on it and back it off counterclockwise. Now open the stop and remove the stem and washer assembly, The stop will begain to drain. When it has quit draining reassemble the stop and move on to the next one. Do this on each one of your angle stops. There will be six of them in a two bath home. When you are done, close off the faucets you have opened, turn on the water to the house, and give yourself a pat on the back.
You have just recharged your air chambers and saved yourself a hefty service call bill.

Hope this helps you out TOM