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We had a new furnace installed about a month ago. 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 said it was likely water hammer because the new Honeywell valves flow twice as much water as the valves that were on the previous furnace. They only suggestions they had were adding padding around the pipes where they leave the furnace room and closing the ball valves on each zone a bit to limit the water flow. Neither suggestion helped.

Would it make sense to try and fasten the heating pipes coming out of the furnace to the walls in the furnace room in an attempt to limit pipe movement and hopefully reduce the sound? Does anyone have any other suggestions?

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.

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3 Answers 3

up vote 4 down vote accepted

It turns out the problem was that the zone valves were installed backwards. They closed in the opposite direction of the flow of water. Since the zone valves were fighting the flow of water, it was causing a great deal of vibration and banging.

I had the heating company come back and reverse the zone valves so they operate in the correct direction. The banging is completely gone.

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... wow. That type of negligence is almost unbelievable. –  Michael Dec 20 '10 at 23:00

As a first step I would secure the pipes properly, remembering to use strapping of the correct material (mixing metals can cause corrosion). This would probably be your cheapest option, and the least time consuming.

You may also find this link helpful.

I noticed the V8043 zone valves have 2 springs and that when the short spring was disconnected, the valve still closed but at a much slower rate. Hence I disconnected the short spring on each of the 4 valves and have been running the system that way for a about a month and have had no problems with a water hammer or with de-energized zone valves being stuck in the open position.

You could also try Air Chambers as described here (Air chambers can lose air over time, and have to be "recharged" from time to time).

The permanent air chamber is simply a vertical section of copper pipe with a cap on the end that is attached with a T-fitting to the supply line near a shutoff valve or appliance. They are installed on both hot and cold water lines. The chamber is filled with air which absorbs the force of the moving water by compressing within the chamber, acting like a shock absorber.

Or if applicable to heating pipes Hammer Arrestors.

Arrestors are sealed units that contain a spring and a waterproof air bladder to absorb the force of the moving water.

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I gated down the ball valves a bit more and that helped a bit. However, that reduces the water flow through the system. I'm going to try securing some of the pipes, but I don't know how much I'll be able to do since I can't access inside the walls without tearing stuff apart. The furnace company was there today to do another service and the guy said he really thinks loose pipes are the problem. –  NYSystemsAnalyst Nov 16 '10 at 16:39

Take a look at @Mike Powell's answer for this question. A water hammer arrestor may be the solution to your problem.

EDIT: @Tester101 brought up a good point about a water hammer arrestor being used for heating pipes. I looked up some max temperature specs here, and it's listed as 250°F for this particular type.

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Can these be used on heating pipes? –  Tester101 Nov 9 '10 at 17:41
    
@Tester101: I looked up max temperature ratings, and they're up above 212°F. So unless there's steam running through the pipes, it should be good to go. Is temperature the only concern? Or did you have something else in mind? –  Doresoom Nov 9 '10 at 17:49

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