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banging radiators

The radiators in my hot-water early-1920's era system bang very loudly when the heat comes on or goes off. It seems to be from the radiators themselves, not from the pipes in the basement. Some of the radiators are quite long--6-10 feet lengths--and those seem to bang more. I'm thinking the radiator legs may be rubbing against the hardwood floors as they metal expands & contracts.

any thoughts?

Re: banging radiators

Banging would indicate water hammer. Popping, squawking, moaning, and screeching is more likely caused by movement while expanding and contracting. If you had steam heat, the answer would be easier. Does this occur when the circulator pump is running, with the gas to the boiler shut off? If you eliminate heat from the equation, such as with room temperature water, you eliminate noises caused by expansion and contraction. Sometimes a loose or disconnected valve disc will hammer and rattle. Does the noise continue the entire time the pump is running?

Re: banging radiators

all you have to do is go through the house and bleed all the radiators. there's air in the system.

Re: banging radiators

As the previous responder said, try bleeding the radiators.

Use Yahoo or Google "How to bleed a radiator", you should get insructions and eevn videos about this.

I don't know about 1920's radiators, but you will need a "key" to turn a valve that releases air/water from the radiator. Find a value stem, where the water pipe is connected to the radiator and look for a square shape bolt head (about 1/4" square). You can buy a radiator key via Amazon.com (ACE hardware, about $3 plus $4 shipping) or borrow one from someone.

I received conflicting advice. Everyone in the internet says to turn off the system when you bleed to avoid hot water scorching you. An home inspector told me the system should be running (water hot with circulator motor running). I don't know . . . . as a start, maybe you should run the system and when you hear hammering, turn it off and bleed one radiator at a time. Conventional advice is to start with the radiator closest to the boiler and work your way forward.

Re: banging radiators

If you have air in the radiators it is not likely you would get water hammer, that's the way a hammer suppressor works. If you have a single pipe steam system, that is only a pipe in one end of the radiator, you need to check and see if the radiators are level or slightly tilted down toward the pipe.


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