DIY Doctor UK DIY Forums

We have an old system and the upstairs rads are now cold suggesting a lot of air in the system. When I try to vent the rads they suck air in and then hot water runs into the header tank from the vent pipe of the hot water heating circuit.
The boiler has now started to switch on/off when the heating is put on. OK when just hot water heating is on.

I tried fitting a tap into the rad circuit near the boiler and use gentle mains pressure to push air out of the rads. It just pushed hot water into the header again from the hot water heating circuit.

any ideas,

Very cold Mike

Have a look at this topic here

https://www.diydoctor.org.uk/forums/view ... hp?t=15441

Hi Mike,

I would check out the pump and MV first.

thanks for the advice, i'll give it a go.

mike