For the past couple of months, the pipes to our shower begin to produce a jackhammering sound and the water begins to pulsate. Turning the hot water down resolves the issue, as does flipping the diverter on the faucet off. The problem seems pretty intermittent and only does so when the water is diverted to the shower. The only change that has occured since the problem began was the replacement of a thermocouple on the hot water heater. Any help of suggestions would be greatly appreciated.