hydronic heat - getting a big bang

Old 12-08-04, 09:50 AM
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hydronic heat - getting a big bang

In the house I purchased a couple years ago I have an old hydronic heating system with 3 zones.

Last winter and this winter I've started to hear a big "BANG" from the boiler. The noise carries through the pipes and can actually 'startle' you because it's so loud.

It didn't do it much when I first turned the boiler on this winter, but now it's doing it more and more.

Also, from a timing standpoint...it seems to make the noise after the boiler or pump or heat "shut's off". I know it's not happening when the thermostat is turning on...it's more after it's turning off.

I'm ready to call the local plumber, but I'd like a verification of what he may tell me.

Does anyone know what could be causing this big bang?
Old 12-08-04, 10:41 AM
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pictures of my system...

Also, when bleeding my system...should I use the bleedling lines attached to the baseboard radiators...or should I use the faucets attached to the boiler as you see in the pictures?

How do you know when to stop bleeding the lines?

Pictures of my system...
Old 12-08-04, 09:13 PM
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If you don't hear air (sounds like water) in the pipes, don't bother bleeding them unless they don't get hot. Check the arrows of flow on the zone valves to be sure they are installed the correct way.


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