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Why do I need to keep bleeding my radiators?

Postby Sieur Cniht » Mon Mar 10, 2008 8:21 pm

I moved into my house about 12 months ago. The gouse has a gas boiler which heats the central heating and water, which from the guarantes was installed about 5 years ago.

My problem is that in my 2 upstairs bathrooms, I have tall towel radiators. Every 1-2 weeks, these are cold at the top, hot at the bottom. Bleeding seems to work, but not for very long.

Why? There are no obviuos leaks and all tanks in the attic are full and the values fully functional. Is there something simple I can do, or is this a plumber job?

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Simply Build It

Postby ALDA » Tue Mar 11, 2008 8:28 pm


I think the "tall" towel rads are probably at the root of your problem.

There should be a fair distance from the highest point in the circuit to the F&E tank greater than the head of the pump.

This creates a positive head of water sufficient to counteract the suction effect which the pump has on a conciderable lenth of circuit, which would otherwise encourage air infiltration.(as in your situation).

Usually a height of 600-700mm from floor to top of highest rad in circuit for the above conditions to be satisfied.

If the pump has "head" adjustment, this may solve your problem.(lower head setting)

If it hasn't got or doesn't solve, then other than fitting lower towel rads, the pump would have to be fitted in the flow pipe and not in the retun pipe as it probably is presently.


The the tanks would have to be raised in the loft.

Hope this has been a help to you.

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Postby Carlton Cole » Tue Oct 04, 2016 2:45 pm

My house is the same, very bad at keeping the heat. Usually the heat sits at the bottom of the radiator. I'm getting someone in to sort it, I think they are going to flush the whole system.
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Postby Dr. Strange » Fri Apr 05, 2019 9:07 pm

It may be a matter of how the system is circulated. Are there circulators? Or is the system a gravity feed?
Are other radiators on the same loop or is this one all by itself?
It may also be a matter of pressure however, I assume that the sunroom is on the main level and that the ones on the upper level are running fine. That being the case then pressure is probably OK. Yet for every 2.3' of elevation you need 1PSI of operating pressure (+3PSI). 10PSI seems a smige low. 10PSI would suggest that the upper level (fan coil in the attic?) is 20' above the boiler.
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