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Banging pipes that wake the dead - please help!

5150 Member Posts: 2
I had a Weil-Mclain Gold CGa Furnace with Erie zone valves installed. The heating in our house is hot water baseboards. Ever since the new furnace was installed, when the heat comes on or turns off, there is a loud bang in the pipes. It's not 100% consistent, but it happens quite often.

We had the furnace company come back to look at the problem. They only suggested adding padding around the pipes but most of the pipes are behind sheetrock.

It sounds way too loud to be air in the pipes and it didn't happen with the old furnace, so something about the new furnace or piping in the furnace room must different enough to be causing this problem.

Have any other suggestions?


  • Ironman
    Ironman Member Posts: 6,971
    Neat Looking Install

    A couple or three things to check:

    1. The zone vales appear to be properly positioned, but confirm that the arrow on the body is pointing upward.

    2. Confirm that the pump is shutting off before the zone valve closes completely.

    3. Pipes expand when heated. Confirm that where there are any changes of direction ( 90deg ells), the piping is not locked against a joist or framing member of the house.

    There preferred placement of the pump is on the supply pumping away from the expansion tank with zone valves on the return. Yours is the reverse of this. Should not be a problem as there are thousands done this way, but under the right combination of circumstances may cause an issue.

    Did your old system have zone valves or two pumps? I'm thinking there's a possibility the valves are closing rapidly while there is still flow in the lines causing the water hammer.

    You may also want to consider installing a delta P pump like the Grundfos "Alpha". It's electronically controlled, variable speed that gives the correct amount of flow at all circumstances(click on the Grundfos ad). You only need about 1/2 the gpm if only one zone is heating. Your boiler and your pocket book will both appreciate it and it may solve the banging if nothing else seems to work (not guaranteed, though).
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
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