Central heating - No water filling the system


Postby donie8472 » Tue Oct 07, 2008 9:09 pm

Having drained the system to add a new radiator, I then released the ball cock to allow the system to refill. However no water is going out of the tank in the attic and into the radiators.

I've opened all of the radiator keys and nothing is happening.

Even when I open the valve which I used to drain the system with, no water is coming out now and the radiators are completely empty. The water tank in the attic is full of water.
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Postby nitro23456 » Wed Oct 08, 2008 8:11 pm

Likely a blockage or airlock in the pipe from the F&E tank.
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Postby AdamsHeating » Thu Oct 09, 2008 3:39 pm

Blow into the expansion pipe (upside down u) that is above the F&E tank. give it some welly though. Watch out because the only way for the air to travel is up behind the potential blockage... in other words the main feed from the f&e so you might get a bit of water blown out.

hope it works
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Postby donie8472 » Sun Oct 12, 2008 7:18 pm

Thanks for the advice.
Unfortunately after blowing as hard as I could there was no change in the situation.
How would I go about sourcing and fixing a blockage in the central heating system?
I think that the blockage is somewhere between the tank in the attic and the radiators upstairs.
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Postby plumbbob » Sun Oct 12, 2008 11:06 pm

A hosepipe connected to the cold tap and pushed against the feed pipe in the header tank often gives enough pressure to remove any blockage. Failing this, the feed pipe needs dismantling and the blockage removed manually.
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Postby tipsychris » Wed Oct 15, 2008 10:50 am

Hi, had a similar problem a few years ago, attempts to bleed the system simply moved the trapped air around from radiator to radiator, and I realised that the feed pipe from the tank was blocked. Blowing down the expansion pipe didnt work even using a water hose, and I was only able to insert a wire a few feet as far as the first awkward corner. the blockage was further down the feed pipe behind the boiler and would have involved major & expensive dismantling. So called in a plumber. My system has a feed pipe and a separate exp pipe, plumber reckoned most newer systems use a shared feed/expansion pipe, and he put in a link pipe between the two, near the tank ( below the feed outlet from the tank), where feed and expansion pipes were close to eachother and accessible. Took him an hour and just a few penn'orth of pipe and unions So now the system effectively tops up from the expansion pipe. That was some years ago & no problem since.
If your feed and expansion pipe are separate, guessing you could do the same
Chris
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Postby plumbbob » Wed Oct 15, 2008 9:52 pm

You won't find designs using a combined feed and expansion pipe in any approved text book, either old or new. Single piped systems arise only because the installer is trying to save on parts and labour. There are various problems that can arise in this arrangement including difficulty in filling and increased possibility of trapped air. If the system was to boil, water is not automatically replaced to refill the system.

Fitting a new link between the expansion and feed to "repair" a blocked pipe, could, in certain circumstances, cause the heating system to be bypassed, and therefore fail to operate. Neither does it repair the true fault. Would you not call that a bodge job?
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Postby tipsychris » Wed Oct 15, 2008 11:19 pm

Can't argue the rights & wrongs with you Bob, cos I'm no plumber. Take your word for it with a new system.
But replacing the pipe would have cost a fortune, what with the inaccessibility and all the making-good.
A bodge? Hmmm, strictly speaking mebbe but the proof of the puddin' in my case is that it did the job, without grief or heavy expense, and that was years ago and no problem since - even with the usual draining down/removal of rads for re-decorating.
So I prefer to call it an innovative solution !
Regards
Chris
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Postby plumbbob » Thu Oct 16, 2008 10:07 pm

Well I guess you have valid points Chris, and maybe with your system other engineers would probably have reached the same same conclusion and as you say, proof of the pudding etc.

Cheers
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Postby tipsychris » Thu Oct 16, 2008 11:33 pm

I'm out in the sticks, no piped gas, so I went for bottled-gas multipoint for hot water and oil-fired boiler for central heating only.
So the central heating has no stored hot water & a simple little feed tank in the loft Mebbe that's why the "short-cut" worked for me
Regards
Chris
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Postby bobplum » Fri Oct 17, 2008 10:13 am

hi
sorry if this is late have you tried back filling the system
bob
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Postby donie8472 » Mon Oct 27, 2008 5:55 pm

Eventually I backfilled the system and bled the radiators to fill them. I connected the garden hose to the valve that I used to drain out the system in the first place. This worked to get the system filled again. I haven't done anymore since as the system runs fine when it is filled. I'm still at a loss as how to source the blockage without it being expensive.
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