Pressure on boiler dropping

Hi,

I have a combi boiler and I'm finding that the pressure on it keeps dropping to almost zero after a few days. The radiators on the ground floor heat up fine but most of the heaters on the the 1st floor of the house don't heat up fully or even at all. I've topped up the boiler twice now only to find the pressure back down to zero. I assume there is a leak somewhere but it's not visible and seeing as the rads on the ground floor are fine the leak is somewhere between the two floors.

I've seen using a leak sealer like fernox might be a solution, does this look like right or am i better off going down the more expensive route of calling in someone to potentially take up floorboards to find the leak?

No leaksealer on combi's unless all else has failed?
Have you checked the prv?
What model boiler?

I've not checked the prv, what should I be looking for?
It's Baxi combi boiler

pipe outside near boiler flue

top pressure up and see if it starts dripping

kevplumb said:

pipe outside near boiler flue ...

Click to expand...

I was gonna say: drops. , but I suppose not everyone knows the prv outlet can be found outside, about a metre under the flue normally.