We have a problem in which we hear this hammering/knocking sound below our floor every time we turn on our hot water faucet or shower - more so in the early morning hours. George (your Field Manager) came today, did an analysis of the problem and told us that instead of replacing the HW copper piping straps he recommends installation of a HW heater circulating pump and add several pipe clamps to the HW piping. George performed the work very professionally but the problem was still there when he tested the HW system. George politely told us that he thinks the problem will go away if we let the circulating pump ran for a few days. He told us to call your office if the water hammer problem does not go away after one week. Ed Espina 2087 Raven Road Pleasanton, CA