: We installed a Lennox complete heat system severy years ago. Because of
: many problems during that time, the Lennox company had the local contractor
: replace the main furnace and water heater unit several times (we have lost
: count). After the last installation, we noted a hammering noise when
: especially the hot water was turned off at a sink. Our heating contractor
: seemed to be of the opinion that it was not related to the furnace
: installation, but that probably the water pressure was too high. So we had
: a local plumber install a pressure reduction valve in the line to the house,
: since the pressure was originally about 100#. They turned it down to about
: 85#, the noise continued, I turned it down to about 55#. The noise
: continues. The same plumber installed a 3/4 inch Sioux water hammer
: arrester in the hot line from the water heater. It seemed to reduce the
: noise, but the sound seems to be telegraphing from another location. Prior
: to the arrestor installation, we installed a Laine hot water circulator at
: our utility room basin (all piping seemed to come from that first). As you
: can guess, we were confused by the fact that we were getting the noise at
: times when we were not turning on and off hot water.....finally coming to
: the realization that the circulating pump was also causing the noise when it
: completed its cycle.

Jerry,
I have had noise problems with the check valve in a recirc line. One solution would be to drill a 1/4" hole in the swing check. Since there is a pressure reducer on the line, it is important that there be an expansion tank for the water heater. The need also increases for mini-resters at locations like the dishwasher, clothes washer and icemaker. Terry