Boiler losing pressure needing topping up

[gillybean]

We have a 10 year old Ferroli Falcon II which we had installed.
Historically we've had problems like this before, last time I think it was the expansion tank needed to be pressured. We have the insurance cover with Ferroli but they now charge if the problem isn't boiler related. We currently have a call logged for Monday so hope it is boiler related!

Not sure if this is the same problem though, pressure keeps dropping and needs topping more frequently, every 10 days or so now. I haven't noticed if the copper pipe outside is leaking can't tell as it's raining so I have attached a plastic bag over the end to check it later!

If there's no water in the bag then from reading on the net it's likely to be somewhere else, can't think where, nothing on the ceilings but more worryingly some pipes are under a solid floor and others downstairs are under Karndean flooring so locating a leak would be a nightmare.

Anyone any other ideas, I think we are covered on our house insurance for water leakage but really don't want to go down that road yet....

[stoneyboy]

gillybean,
You've covered most options: failed expansion vessel, leak somewhere, could be a failing pressure relief valve.
end

[Letsrock]

I've just experienced the self same problem. I too have a rake of pipework under the floor so appreciate the fear associated with this kind of pressure drop.

Given the system is pressured I'm assuming you have a condensing boiler and that the boiler itslef has a condensate expansion pipe which typically leaves the house via a plastic pipe and goes quietly underground into a soakaway near the outside wall next to the boiler or maybe into a drain etc.

In my case - the heat exchanger on the boiler had packed up and water (hence pressure) was leaking down this pipe like a sieve. Because the pipe is closed its impossible to check it without cutting it first. Also because a previous engineer told us that any pressure drop was extremely unlikely to be caused by boiler failure - we pretty much ruled out that cause and didnt go to the trouble of cutting the pipe. Rather we assumed there was an underfloor leak somewhere which was going down not up hence was not obvious in exterior mould, mildew etc.

Dam expensive assumption that because I ended up hiring a team of leak detection specialists for £500 who "found" a leak!!! One which didnt exist in fact but they justifed their extortionate charge!! Luckily, not being a complete plank, I didnt believe it so didnt excavate my beautiful tiled floor and screed at their suggestion.

The busted heat exchanger was caused by corrosion from air in the system.....lesson learned - dont skimp on corrosion inhibitor kids!