Air Lock Woe


4 Jan 2007
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United Kingdom
Hi all,

I removed a downstairs radiator to drain some of the system volume so I could run a sludge remover/cleaning solution through for a couple of days prior to getting a new boiler fitted. I currently have an open system with gravity hot water.

Now I can't seem to get the heating system to circulate and can't bleed all of the radiators (I got some air out, but then no water or air). The pump is running and the water seems to be cold directly above it although I've tried undoing the bleed screw and I'm getting water coming out.

After searching on here it would suggest an air lock or a blocked cold feed. The problem is that the cold feed is connected to the hot water return to the boiler from the cylinder and the hot water is fine so it would seem like an air lock. As the water feels like it isn't circulating above the pump, is shutting off other rad valves likely to work?

Just wondering if anyone can offer any advice?

Thanks in advance!
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i would say a blocked feed

D'oh! Was hoping it wouldn't be that!

It just puzzled me how it could be that as the cold feed is connected to the return from the cylinder and the hot water seems to be working fine (it's gravity hot water so the boiler has heating flow and return and cylinder flow and return.

Mind you if enough crud has got down into the boiler it could be blocked there I suppose.

Oh well the whole lot's coming out tomorrow so just wasted a bit of time and money putting the sludge remover in :cry:
when you drain the system check the f/e tank in loft if that doesn't empty then you know you had a block in the cold feed.
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