central heating loses pressure when I use hot water tap

[crapday]

I have an old Glowworm combi gas boiler. When I use the hot tap in the upstair bathroom, I loose water from my central heating system.

I have filled up the system with water up to 1.5 bar. I then bleed the rads and re-pressurise the system to 1.5 bar again. This seem to be fine, but as soon as I use the bathroom hot water tap on the sink (not noticed it with the bath) I hear the rads bubbling as water is drained from them.

I have googled this problem but cant find answers anywhere. All help is very much appreciated.

Gary.

 

[thebug]

Could be the diverter valve not fully changing over?

 

[picasso]

personally I would have said its impossible but you never know.

 

[ianmcd]

personally I would have said its impossible but you never know.

As Picasso said the only way this could be possible is if you have connected that HW tap to a radiator pipe the divertor valve being faulty could not cause this

 

[Dan Robinson]

Or the EV is goosed - pressure rockets when tap is run; PRV blows.

By the time the OP is finished upstairs and gone down, the boiler has cooled, the pressure has dropped and Mr Boiler is sat there with low pressure.

 

[ianmcd]

Or the EV is goosed - pressure rockets when tap is run; PRV blows.

By the time the OP is finished upstairs and gone down, the boiler has cooled, the pressure has dropped and Mr Boiler is sat there with low pressure.

OP says it only happens with 1 tap on the bathroom sink Dan and doesnt happen with the bath tap in the same bathroom

 

[Dan Robinson]

Didn't see that bit...

But applying a little logic - bath has higher flow rate. Boiler doesn't get as hot.

Basin taps can have less than half the flow of a bath.


But then again - could be talking total boolax.

 

[crapday]

Hi, thanks for the replies. Looking to get a new boilers soon as this one is 24 years old Older than my sons lol.

seen good reviews on heatline as they are now owned by Valiant. Just want something with a 2 year warranty as after this will be going back to BG with their boiler repair plans.


Gary.