tank overflow

[Newby2]

I am new to this forum but I would appreciate any advice/help.

My house has a typical central heating system: hot water cylinder in the airing cupboard, traditional boiler, two water tanks in the loft.

On Monday night when the heating was shut off I bled 2 radiators. Then on Tuesday morning when the heating was switched on, I found one of the overflow pipes below my roof (I think it is from the big cold water tank in the loft) gushing out some water. After a while, it became dripping. I have observed for 2 days and it seems that there is no dripping when the heating is turned off, but there is a slow dripping when the heating turns on. I am not sure it is the ball valve problem, cos it happened rightly after I bled the radiators so would it be possible that water entering the cold water tank from somewhere else (rather than via the ball valve) to cause it overflow??

Any possible cause of this? Thanks in advance.

 

[ChrisR]

You're going to have to get out your crampons and ice axe and venture into the void which lurks above your loft hatch.

It's quite likely that the float valve, once disturbed by your radiator-bleeding, didn't seat properly so it needs a clean and a new washer.

Careful, there are ghoulies up there.