REfilling a central heated system

24 Oct 2006
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United Kingdom
Hello, I have an open vented central heating system and I turned of the mains water and bled the radiators added flush cleaner to the expansion tank. I closed all the radiators and turned on the mains water but the system isnt refilling. The expansion tank is half full of water and the ball in it functions correctly. Can anybody help? The house was built by Mclean 10 years ago and the boiler is an ideal classic. what is the path of water into the central heating system? I am guessing that i am looking for a stop cock somewhere but i've tried the ones in the storage tank cupboard.
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Well what i did do was attach a hose to the kitchen radiator and opened up the drain off. It had a straight drain off unlike most angled ones, inf fact all of the downstairs radiators have them so I drained the lot and opened up the bleed valves upstairs. How do I drain the WHOLE system then? any tips please
From what you've posted you already have drained the system.

In your airing cupboard, assuming you have a standard hw cylinder, there will be a cold fill pipe with a gate valve in it that is teed into the system pipe work. Check this valve is fully open.

If it is then it sounds like you have a blockage in the cold feed.

This will be where the cold feed tees into the rest of the pipe work.

Cut this out and replace.

If you have a boilermate then post back as this is different.
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I re-drained all the radiators and still the expansion tank would not go down so I will take your advice that the feeder is blocked. Rather than cut out the pipe could I siphon the water from the entry into the expansion tank, put some kind if cleaner down there or perhaps a pipe/drain cleaner rod?.
The expansion tank is quite mucky with silt. Any ideas I could try other than cutting the pipe? as it is in a difficult to place to get at.
you will have to cut it

if you can't get the Tee out you could cut it higher and poke some wire or welding rod down there

but this will dislodge lumps of black sediment which will do no good and may lodge in the pump or boiler. If it was me I would fit a Magnaclean on the return pipe to the boiler first, it will trap the black sediment on a powerful magnet and prevent it circulating and causing damage or blockages. Then you can add a chemical such as X400 which will break down the sediment so it flows round suspended in the water (and the Magnaclean will then trap it)

Until you have cleared the blockage water will not flow down from the F&E to take any chemical to it.

Bale out all that sludge from the F&E first

To get the heating working tonight, you can refill the system by putting a hosepipe on the drain cock. Fill it from the hot tap not the cold main to prevent mains pressure causing any damage until you are sure the pressure can escape from the vent pipe. There is a very faint chance that filling it from the bottom might dislodge the blockage.

If you have not already bought some, buy your cleaning chemical. It will cost you about £15. Do not put it in the F&E until you can see that the F&E is flowing down into the system, and add it during filling, not after the system is full. Bale out all the sludge from the F&E because you don't want any more in the system than you have already got.

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