Im baffled with this drop in pressure

kevhky · 18 Apr 2010

This is totally baffling me

Combi boiler
i top the boiler up (ch) to 1 bar, after around 24 hours the pressure drops to zero (heating running throughout via room stat)

I then top boiler up (ch) to 2 bar turn heating completely off for 24 hours and no loss in pressure

During this time dhw is being used

I check everywhere for leaks no sign what so ever pipework/prv/rads under boiler absolutely nothing at all

Scratching my head with this one

Gasman77 · 18 Apr 2010

Any pipes screeded in the floor?

kevhky · 18 Apr 2010

Gasman77 said:
Any pipes screeded in the floor?

No, all under floorboards

markymark1234567 · 18 Apr 2010

Sound like the pressure vessel is knackered. Feel the prv pipe see if it gets warm or find where it terminates outside i bet it is wet.

Gasman77 · 18 Apr 2010

Downstairs too? you need to let the system go cold as it will be evaporating when hot

Also try isolating the boiler over night and see if it drops - if it does you know the leak is in there!

Gasman77 · 18 Apr 2010

The OP said he checked the prv!

kevhky · 18 Apr 2010

markymark1234567 said:
Sound like the pressure vessel is knackered. Feel the prv pipe see if it gets warm or find where it terminates outside i bet it is wet.

Prv is dry as sticks outside

kevhky · 18 Apr 2010

Gasman77 said:
Downstairs too? you need to let the system go cold as it will be evaporating when hot

Also try isolating the boiler over night and see if it drops - if it does you know the leak is in there!

I let the system go cold overnight, then topped it to the 2 bar, 24 hours later still sittin at 2 bar,

both upstairs and down all pipework runs under beams

Blackadder43 · 18 Apr 2010

Just to 100% take the prv out of the equation stick a ballon over the end of the pipe while you are running the heating........

kevhky · 18 Apr 2010

Blackadder43";p=" said:
Just to 100% take the prv out of the equation stick a ballon over the end of the pipe while you are running the heating........

ive done that and not a drop in sight

Blackadder43 · 18 Apr 2010

Then its methodicaly check every pipe run as soon as the pressure drops.....
Good luck

doitall · 19 Apr 2010

Could be the plate HX is pin holed.

Does the gauge go up and down if you open and close a hot tap

DP · 19 Apr 2010

John, that is not possible.

twgas · 19 Apr 2010

kevhky said:
Blackadder43";p=" said:

Just to 100% take the prv out of the equation stick a ballon over the end of the pipe while you are running the heating........

Click to expand...

ive done that and not a drop in sight

I dont think you tried this for long enough (34mins between suggestion and your result post). try it again, for 24 hours, from cold @ 1bar, and watch the pressure gauge as the system heats up.

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Im baffled with this drop in pressure

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