I am using a gas-fired water heater to run a loop of hot water baseboard. The problem is the pump causes the baseboards in the house to "ring", not very loud but loud enough to be annoying. The pump is mounted in-line of the supply line to the radiators. The pump itself seems very quiet. The lines are well supported 3/4 L copper. You can grab the line and muffle the sound a little. I've checked for binding pipes. Is the problem that there is not enough mass,[like if the circulator was attached to a boiler]?Is there a way to isolate the pump somehow? Perhaps use a different pipe on either side of the circulator.