DIY Doctor UK DIY Forums

I have an open vented heating and hot water system with a glow worm boiler and a pump in the loft. I live in a bungalow. On Saturday (23 Dec) I found a leak in a shut-off valve in the inflow pipe to the boiler. I drained the system and replaced the valve. No problems...solved the leak.

On restarting the central heating however, the pump was very noisy and no heat was getting to the radiators. I bled them all but no joy. The nearest radiator to the boiler (and the pump) would not bleed (no water would come out even with the screw fully removed) I suspected an air lock and ran the mains pressure through the hot water system. This quietened the pump a bit but still no heat to either the heating or the hot water tank. Boiler fires up ok but soon cuts out and outflow pipe gets warm for a few feet but no further. I suspect the pump (it's still noisy) has 'gone' but it is obviously not 'dead' as it is making a noise.

Phoned a plumber who couldn't help but who said I may have started the heating too soon and 'fried' the pump.

Any ideas anyone before I go and buy a pump?

Thanks in anticipation.

Ok, i think you might be alright. just go in to the loft and bleed directly from the pump. their is a big silver screw in the center ( grundfos, dab). or a big plastic nut (myson ) also i would expect that there are some other bleed points above the boiler in the loft. possably at both ends of the pipe run. This is def an air lock. ps turn off the power or you will burn out the pump.

Thanks Ollie I'll try that. I'll let you know how I get on. Thanks again.

Ollie,

Thanks you're a wizard, it was an ailock and now at least I have some heating. However I still have a problem. Remember I live in a bungalow. There are six radiators in all. 3 are working fine (lickily the main 3 the lounge, main bedroom and the bathroom. The other 3 are stone cold and bleeding them doesn't seem to make any difference.

The bathroom radiator is working but the hallway one which is on the other side of a partition wall, 3 or 4 inches away isn't! The main bedroom one is working but the other bedroom one, about the same distance away isn't! The one in the kitchen which is nearest the boiler and almost directly under the pump location in the loft isn't working. When I bleed them water comes out like a fireman's hose but they won't warm up.

At least the house is now comfortable though. Any ideas?

PS. The pump is now quieter than it has ever been so I've probably had a problem for some time without knowing it.

you still have an air lock. turn off all the rads that work and turn the boiler stat off, then turn on the heating you should hear the air lock move to a rad or into the loft where you can bleed it.

Thanks Ollie. That got it. I can't say I actually heard anything but I did what you recommended and bled the three short vertical pipes rising from the pipework in the loft It's now fine....and what's more the pump is now completely silent! (is that just a coincidence...or my imagination?)

Thanks again.

Good glad i could help.