We had a shower faucet that was leaking. It was a single handle Moen. I went to Home Depot and got the correct replacement stem. After replacing the stem if anyone turns on and off the cold water the pipes start knocking. It sounds like it is coming from right above the shower faucet. I Googled the problem and most said to turn off the water to the house which I did. Open all sillcocks and faucets in the house and leave open for about an hour. I did this. Turned on the water and started closing the valves and faucets. Still have the problem. Don't really want to start taking drywall off to find the problem since I didn't have this problem before changing the stem.
I can't get to the pipes that are hammering without removing drywall. Since I have a water heater in my attic can't I cut the cold input and solder in a tee with a copper stand pipe in that and cap it off. Will that do the same thing? If so how long should the stand pipe be? If that won't work who handles an accumulator. HD & Lowes don't show having them.