Hello, I have a problem, I have a hot water boiler system with 2 area zones providing heat for my rancher. On occasion I hear this large bang sound, I was advised to release any trapped air from this relief valve which is at the highest point above my boiler.
I have turned off my boiler for about 2 hrs so any air that is in my system will eventually rise to this high point relief screw, which I expelled some air, you can actually hear this. I close the screw as soon as the water comes out, turn on the boiler once again, works OK till again I heard this loud hammer bang sound hours later which is very annoying. I again expelled the relief screw where only water comes out. Why am I still getting these intermittent bangs? I have even bled this valve with the pump running.
( I have bled all the floor radiators)

Thanks for any advise,

Regards, Arthur

Thanks for any advise,
Dear Arthur :

There simply must be a lot of trapped air in the system. Was the system recently repaired? Or did it do this already for a long time?
Just keep releasing the air, and the problem in the end will stop doing that. Nobody however can tell you how long that can take!
.
The bangs are resulting from water columns hitting on other water columns, when air in between them finds a temporal internal hiding place. Isn't there a water hammer arrestor in the system?
Success!
;)

Hello, I had the water pump replaced about 3 weeks ago, this hammering started few days ago.
What is a water hammer arrestor?
Thanks for your response.

Arthur

What is a water hammer arrestor?

It is a device that has a air cushion built in and usually placed high in the boiler water lines. They are also used for domestic water supplys where water hammer is a problem especially when you turn the water off and stop the flow. Then you get the hammer. This is also the same problem as when the boiler pump turns off then you can also get water hammer.


Water hammer - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Water_hammer)

OK, I will to continue to bleed this relief valve, should I do this when the pump is running or do I need to turn off the thermostat for a couple of hrs. I have only heard air hissing out when I shut the system down for this amount of time. Any suggestions will be appreciated.
I will look into this hammer arrestor.

Regards, Arthur

You can bleed at anytime. Usually the highest bleeder in the system is the most trouble. I hope you have a auto fill valve in the cold water feed to the boiler. If not you will have to manually add water after each bleed.

I never hear air hissing out when the system is running or when the pipes are hot. If air is caught somewhere in the pipes, does the air have a better chance to rise when it's a little cool?