How do I refill my heating system?



I have a radiator that is cold whilst the others are hot. I am thinking that it may need bleeding or that the thermostatic valve may need changing.

Either way if I have to top up the sytem after bleeding or if I have to drain the system to replace the valve how do I refil the system?

My old house had a combi boiler and so I could just use the refilling loop and get it back up to pressure.

The current system I have is a Baxi boiler with a hot water tank and to be honest I don't yet know where the water comes from for the central heating system? would it be sealed system.

Anyway what I don't want to do is to not be able to fill it up should I need to and hence make all the other radiators not work!

The boiler is a Baxi Sole HE condensing boiler. there is a small grey water tank / tub on the shelf above the big red lagged hot water tank.

On a curious note are the hotwater and heating water systems separate? I presumbed / thought that the water in the heating system stayed the same and just went around and around in a sealed system with the water being heated by the boiler.

Any help is very much appreciated.

macgrl :)
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12 Dec 2008
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United Kingdom
Sounds like you have an open vented system. If you look in the instruction manual of your boiler there will be schematics of the various system configurations. The grey tank should top up the system.


Hi. Thanks so much for your reply. The grey tank in on the shelf above the hot water tank. I can't see in it as it is so close up to the ceiling. Would it have a ball cock type valve and when more water is needed, for example if I were to bleed the radiators and more water was then needed in them?

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