Water level in header tank question.

[pcr]

Would appreciate some advice.

I am trying to find where air is getting into the central heating system.

The system is standard semi-pumped with conventional boiler at ground level, pump in CH return pipe next to boiler, feed and vent pipes are each side of the cylinder coil on first floor.

When turning the pump on and off repeatedly, the water level in the header tank rises by approx' 8mm when pump turns on and falls back when pump turns off. There is no pump-over.

I wonder if this is normal. I assume that the position of the pump is such that it will try to force water up the gravity HW pipes, but don't understand what displaces the water elsewhere in the system.

Thanks.

 

[Softus]

What are the original symptoms of the problem?

And please don't say that it's an 8mm rise in the F&E water level.

 

[kirkgas]

the pump wont pump the water up the gravity side, (or it wouldnt be gravity!!!) expansion of 8mm is probably due to the water being heated and expanding,
one question springs to mind from your question, why were you in the loft measuring an 8mm expansion of water

 

[Bambergaspipe]

I am trying to find where air is getting into the central heating system.

In your case normally the loft. if that is where the tank is situated that feeds your heating system. It`s open to the atmosphere you see. and the atmosphere has ways of jumping into your tank and wandering your system causing all sorts o f mayhem...it`s a Bummer.