Expansion tank overflow

TallTree

My central heating expansion tank is overflowing, I've checked the ball !!!! valve and it is operating properly, the water is flowing into the tank through a different pipe and the water is hot. Anyone know what is causing this and what I can do about it?

raymond

Do you have thermostatic radiator valves ?

It sounds like the water has no radiators to go round so is being pumped back up the expansion pipe into the hearer tank.

TallTree

no thermostatics, but a couple of the downstairs rads are cold at the bottom, do I need to drain it all down and flush the rads?

TallTree

Turned out the pump had seized with a blockage of rust n stuff, the boiler was still coming on somehow causing an overflow in the header tank. I changed the pump, now everything is fine