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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 5648
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have an old boiler with a large expansion tank, We

Customer Question

I have an old boiler with a large expansion tank,
JA: I'll do all I can to help. How long have you been dealing with this?
Customer: We recently drained the system to repair radiators and refilled
JA: How long has this been going on? And how severe is the problem?
Customer: now it makes banging noise and the pipes are really hot
JA: Do you plan on doing the work yourself?
Customer: yes
JA: Anything else we should know to help you best?
Customer: to eliminate the problem i release the pressure releif valve and then it stops
Submitted: 1 month ago.
Category: HVAC
Expert:  Rick replied 1 month ago.

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.

Pipes in a hot water system only bang when the water is too hot (near or above 212) and there is air in the system. When the too hot water meets an air pocket it flashes to steam and BANG. I'd suggest you bleed the radiators again and either turn the water temp down or replace the aquastat that is controlling the water temp. An old hot water system with radiators typically functions with water in the 160-170 degree range. Well below the boiling point.

Expert:  Rick replied 1 month ago.

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