Plumbing help - bleed hot water back into central heating?

[aww999]

Hi folks, I had to move some radiator pipes today so I have drained the system down, now I've finished I'm not sure how to get water back into it!

I closed off the ballvalve in the loft for the central heating header tank, turned off all the radiators at both ends so I didn't have to drain all the water out of them, andd then used the drain cock in the kitchen to empty all the water out of the pipes.

I've done the piping, and opened the loft ball valve so the header tank is now full. However when I open the draincock downstairs nothing comes out, no air, no water, nothing!

Should I switch the central heating on so that the pump gets things going, or am I liable to damage the heat exchanger in the boiler (or the pump itself) if I run it dry? Or do I need to open up all the radiator valves and open the radiator bleeds?

[ferg]

You could try running the pump for a short period incase it has airlocked. Turn the boiler off first though.
Worst case scenario is that the cold feed into the sytem has blocked when you drained it down. Is the header tank sludgy?

[Silver993tt]

Have you tried bleeding the radiators, maybe the water has now moved in the system (with some air) and you have an airlock or 2. See if any air comes out of the radiators. If not, try and connect a hose to a mains supply and then to your heating system drain cock. Allow mains pressure water to pass thru the system and listen for gurgling in the header tank as air possibly escapes into the tank.

Any of the valves you closed off just keep on turning now do they? Are they gate valves? If so, possibly the spindle has rusted thru and allowed the "gate" to drop and hence close the valve. I had that last week, not on the heating system but on the 2 upstairs cold water feeds. Had to change both gate valves.

Edited by Silver993tt on Sunday 16th November 17:18

[V12Les]

You should find that opening some bleed valves will do the trick.