Eurocombi pressure drop

[dogz]

Hi, I've a Eurocombi Sx 20 MFFICE combi boiler. recently the pressure has been dropping over a day or so. I've recharged the expansion vessel and tweaked up all slightly leaking radiator valves.

No signs of any drips from the prv, or under the floorboards near the rads.

When I shut off the flow and return valves the pressure stays up, which suggest to me a leak in the central heating pipes somewhere. Hope i'm wrong. Don't want to rip up all the nice flooring and floorboards in the house.

I thought i'd prove it by leaving the valves shut off for a few days and then, assuming a leak in the pipework would drain them down, turning them back on and seeing if the pressure plummeted. All that happened was an instant drop of a few points and then back down to zero over the course of the day.

Any ideas?

 

[ChrisR]

<drain them down,>
did you mean that?

Can't think of anything quickly that you haven't already.

 

[dogz]

Sorry, I meant if there is a leak in the pipes (flow or return side), then it would drain enough over the course of a few days to show as an immediate pressure drop when I opened up the flow and return valves again.

Am I right in assuming this, and that the pressure staying up when the valves are shut off indicates a leak in the pipework and nowhere else?

Thanks for the help.

 

[ChrisR]

Yes you are. That's the problem - can't think of anything you haven't!

If the ch pipes are exposed anywhere like where they go up/down, you could put iso valves in to narrow down the area with the problem.