Hammer in CH System on Start-up

[revinkevin]

This problem seems to crop up and yet I have not found the answer to my problem so far. Our CH system emits a loud bang from the pipes on start-up and at no other time. It is micro-bore and quite old - like 30 years. I note that we have NOT had to bleed the radiators for a long time. There is no air our highest radiator. The water in the tank is much hotter than it used to be. The pump is relatively new as is the 3-way valve. We have set the HW to come on just before the CH but I am not sure that it does. I would really appreciate some definite advice.

 

[Porque223]

Install an anti-water-hammer device?

 

[revinkevin]

I could do - but the problem has only manifest itself in the last few months. Something has changed in a system that never had the problem

 

[Porque223]

Try to get more clues by partially closing your water valve. Use a garden hose to localize the noise source. Clamp the pipes in various places to check if this damps out the noise. Check for excessive water pressure, over here the range is 20 PSI for health reasons to 80 PSI for pipe and parts lifetimes.