I have base board heating in my house, two zones. Once my thermostat triggers the valves to open I can hear creaking in certain places in my house. I understand that the pipes are expanding as a result of the hot water flowing through. My problem is once the thermostat reaches it's shut off temperature there are a couple of bangs though out the house. I'm assuming there is a build up of pressure and once the heat turns off the pressure is relieved, as a result the pipes are hitting the joists. Is this my problem and if so what can I do to resolve?

Probably your guess is close. If you can pinpoint exactly where the banging occurs, and if it is accessible, you can cushion the pipe where it might be contacting the structure.

A valve shutting too fast will cause water hammer. If you can slow down the valve it will go away (if thats the problem). Also a stand pipe that traps air will cushin the whole system.

Richard, the banging is in two or three places between floors. I would have to break open the ceiling to gett to these trouble spots. I'm hoping that I can do something where the furnace is.

ibken,
Thanks for feedback. How do I slow down the valve from opening. What is a stand pipe? Does it work the same as expanable tank? I have a expandable tank on the same line as my two shut off valves. How do I know if this is working?

http://www.plumbingsupply.com/waterhammerarresters.html
Yes, an expansion tank and stand pipe are pretty much the same thing. If the expansion tank is before the shutoff valve it may not prevent hammering. I have shattered a 3in. pvc drain line by shutting it too fast. The end of the pipe was open to the atmosphere, so even if you allow the liquid to expand "downstream" it can still hammer. Just try one of the water hammer arresters just past the shut off valve. Just buy one at your local plumbing supply store. Hope this helps.

This message has been edited. Last edited by: ibken,