The vent pipe has been extended as far as possible and still there is pump over. Looks like I'll have to get the magnet out to see if I can find a blockage.
Thanks for the help
Hot water is pumping back to the feed tank of my central heating system. A de-aerator has been fitted by a plumber but to no effect. A plumber has also fitted a valve on the feed pipe but that results in the water feeding back up the vent pipe.I have now left the valve open. All radiators have...