Filling Loop Problem

Postby glynh » Wed Jan 06, 2010 10:03 pm


My boiler's working fine, hot water, radiators all working normally, but I noticed the pressure gauge was getting low and went to add some water from the mains via the filling loop. This is just two taps - heating system on one side and mains on the other. Between the taps there's a short flexible pipe with braiding.

This has always worked fine in the past. You open each tap in turn, hear the mains water rushing through the pipe and then close both taps again. Pressure goes up and all's well for another several months.

But no joy now. I open both taps and there's no flow at all. Pressure remains where it was. Any ideas about how to fix this? And what eventually happens if I just keep running the system without being able to top up the pressure?

Any help gratefully received. Cheers.
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Joined: Wed Jan 06, 2010 9:22 pm


Simply Build It

Postby plumbbob » Fri Jan 08, 2010 12:40 am

Has the water frozen?

It may be the plastic handle on the tap is broken and not actually opening one of the valves.

Once the pressure drops below about half a bar (depending on the model of boiler), the boiler will trip and stop working until the pressure is restored.
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Joined: Wed May 07, 2008 9:59 pm

Postby glynh » Fri Jan 08, 2010 12:30 pm

CHeers for that.

I fixed it. Realised that I could take the flexible pipe out which allowed me to narrow it down to the tap on the mains side. Nothing came out when I opened it while the other tap allowed water out from the heating system.

So I turned off the mains at the stop cock and replaced the offending tap with one of those connectors you open and close with a screwdriver. Problem solved. Looking at the faulty tap it seems it was a clogged up and the little black washer wasn't moving when the tap was turned.

Good to know that the boiler wasn't going to explode.
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Joined: Wed Jan 06, 2010 9:22 pm

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