Lost Cold Water, now can't get hot

[andi-c]

We have had a burst water pipe near our home and lost cold water for around 30 hours, since it's been fixed and turned on, our hot water pressure has never returned.

I have a combi boilder, Valiant Ecomax that shows no errors, pressure dial is just under the max reading and the pipes surrounding the boiler are all heated, the heating system is fine all radiators work fine there's just not even a drip coming out of any hot taps. (Cold water pressure fine)

Not a good time on Xmas Eve, BG say they can't come out until Thurs and Yorkshire water say the fault is theirs but they can't send anyone out to fix it as it will be a BG issue now.

Any pointers, tips or even solutions would be a major help, nobody on the phones from either company will even say what they will do when they come out and of course we're not a priorety as we're neither old or have children despite paying monthly boiler, pipes and heater cover payments to BG.

[marrtin]

Are you sure someone didn't turn a valve off when the burst was being mended? I can't see what could cause the water to stop flowing apart from debris entering the system, and that's pretty remote.

You say the pressure is just under max. It should be between 1.0 and 2.0 bar (or in the green area if no scale).

[andi-c]

It's just under the red mark, it feels more like a block than anything as all the pipes around the boiler are hot, the tank in the loft is all full and working pumping the cold in.

[marrtin]

Oh, I assumed you have a combi boiler so the hot water is at mains pressure. By your description, it sounds as if you have a pressurised heating system, and your hot water is vented low pressure with header tank and hot cylinder in an airing cupboard?

If so you probably have an airlock. You need to force high pressure cold water up a hot tap to push the air back into the header tank. If you have a mixer tap turn on the hot, block the outlet with your finger and turn on the cold for 5 - 10 seconds.

You could use a length of hose between hot and cold taps.

I have cleared this problem before by sucking the hot tap as if starting a syphon to run.

[andi-c]

You were quite correct, connecting the hot and cold and backing the supply up worked a treat, thanks for your help.