F and E Tank Overflowing

[sjpv5]

I have a gas fired central heating system - boiler is about 15 years old with 11 rads. Normal open vented system

The F and E tank is overflowing - just a steady dribble - but only when the boiler is off. When the boiler fires up - for hot water and / or central heating - the overflow soon stops. When the boiler turns off, after a while, it starts overflowing again.

The only work I have has carried out recently was a replacement 3 port valve ( the rads were coming on when only the hot water was selected). After this the overflow problem started. The plumber thought it might be the pump (we found that it was installed upside down since new - 15 years plus!) so a new one was installed - the right way around, but the problem persists. He also replaced the ball valve in the F and E tank, to make sure it was working OK. British Gas suggested a Powerflush - but at £600 it seems excessive for such a small problem! Any ideas?[/b]

 

[gas4you]

Could be simple like the ball valve washer is knackered and does not switch off completley so the f&e tank is too full from the start. When pump kicks in system pulls level to below overflow outlet.

Could be a bit of muck has got on the valve seat.

 

[John_D]

is the cold water storage cistern higher ? I have had 2 cylinders with internal leak recently. The CWSC water goes into the DHW cylinder and enters the heating coil through the leak, then rises to the F&E header and overflows out of the warning pipe
the radiators also get warm to the temperature of the DHW

when not using water check if the CWSC ball valve is trickling water in


if so you needed a new cylinder and still do