Banging Pipe Question

I had to install a new shower faucet a while back and in doing so I when ahead installed a couple of shutoff valves. Since then we have the worst pipe banging that you could imagine. My question is why would installing these valves cause this and secondly what can I do about it?

Thanks in advance for your help!

What kind of shutoff valves, and where did you locate them?

I used ball valves and they are installed in the center of each line. I have attached a pic for you to review.

Ball valves are not known for causing water hammer, as there are no parts inside of them that can vibrate or move as water flows through them. I wanted to make sure that you hadn't used globe valves, as they can cause hammer if the washer is loose, or they are installed backwards.

By chance, are there also valves on either side of the shower valve, that came with the valve? I have seen these valves cause your problem.

There were no valves on the shower, that is why I went ahead and put them in. Yesterday, I bleed all the lines and there did seem to be a lot of air in the line, especially in the shower. I also went and foamed all of the pipes where I thought they possible could rattle. The banging is not near as bad, but I have done this procedure before and eventually it always comes back. Bottom line is that I am very confident that it is air in the lines causing the problem and that it is isolated to the shower. Is there something I can do that would stop the air from building in the lines?

How about adding a "Hammer Arrestor"?

I am still dealing with banging pipes. I had someone tell me to check the pressure in the water expansion tank, it was 35 psi, they said to take it up to 75 psi, so I did and the pipes are still banging. My next step is to add a couple of water arresters, but not sure where the best place would be to install them. Should I put them in line, near where I installed the shut off valves. (See pic in above post)

Check pressure to house should between 60 to 65 psi also make sure all shutoff valves in house are open all the way. These would be the ones to your faucets toilets and laundry. If you have an expansion tank the pressure to the tank should be set to same pressure as house not lower. It will not do its job

Install the hammer arrestors as close as possible to the fixture that is causing the water hammer.

What brand of valve did you install?

Taking up the water pressure will only make the problem worse not better. The ball valves are not the source of the problem. More likely the shut off valve you installed. Take the pressure back down to 35 psi. The hammer is caused by a shock wave driven from the closing of the shut off valve (but you already know that) and you want to slow the wave down. The arrestor is designed to do that. Alternatively you could put some elbows in those straights runs of pipe and that would also slow down the velocity and act as a damper.

Aces Four

Thanks for the info. I am going to put in a couple of water arrestors, do you think that installing between the shutoff valves (pictured) and the fixture will work okay?