Combi Boiler - How often should it be topped up?

Hi,
I have a Worcester Bosch Greenstar 27CDi boiler. It should be kept at 1.5 bar, but it tends to drop after a couple of weeks, and I need to top it up again.
Is this normal please, or is there a leak?
Thanks,
Paul.
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In message

no
yes
--
geoff

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Paul was thinking very hard :

If there is a need to top them up, then there logically must be a leak or pressure loss somewhere. It could be that the pressure vessel is low on air, such that as the water heats up instead of the vessel being able to accommodate the expansion, it is blown out via the pressure relief valve.
Other than that it might be a leak at a valve, TRV, or from a pipe, or joint. These leaks can be very difficult to find, because you don't need to actually loose much water for the pressure to go down. If you really cannot trace it, the best way is to drain the system completely and find some way to pressurise it with just air. Air leaks out much more easily than water and therefore produces a noise which can be traced.
--
Regards,
Harry (M1BYT) (L)
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Harry Bloomfield wrote:

That typically does not present as a gradual pressure loss over weeks. It normally presents as a catastrophic pressure loss after one heat cycle.
Also easily tested by taping a plastic bag over the vent pipe to capture any release.

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wrote:

My system 9and otehrs I think) has a little 'float' valve to automatically vent air form the system so you couldn't pressureise it just with air.
Robert
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The pressure relief valve inside the boiler can leak. I used to have to top up the pressure every few months but recently it was needing it every few days. Since the boiler is under contract I called in WB and they replaced the PRV and now it is OK.
Archie.
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Mine does the same and it is the pressure relief value (waiting for it to be replaced). Put a bag over the end of the outside outlet and see if it is dripping.
Never know, might be the same thing and an easy fix if it is.
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OK, many thanks for the answers, hope it's the PRV then....
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