First, make sure the valves leadong to the shower are fully opened. You may have a valve in the basement to shut off the water to the risers for the second floor (assuming this shower is on the second floor), valves directly behind the shower, and, if it is a Moen shower faucet there may be internal valves inside the faucet. To check for the internal valves, remove the large round coverplate under the handle, and look in the hole for two "screws" that can be turned with a straight blade (not phillips) screwdriver and make sure they are fully open. If that doesn't fix the problem you can buy or make hammer arrestors and solder them on to the hot water pipe. Basically they are simply a 6 inch piece of larger diameter copper pipe with a cap on it. If your existing supply pipe is 1/2" you would use 3/4" pipe for the arrestor. This creates a trapped column of air that will act as a cushion as the water goes on and off. Google "water hammer arrestor" for more information.
Sent from my LG-D415 using Tapatalk
Sent from my LG-D415 using Tapatalk
