Combi boiler slowly losing pressure

Hello,

The water pressure in my combi boiler slowly drops. I normally fill it up to around 1 bar and it takes around a month for the pressure to drop down to near zero - which makes for a cold house when I get back from work.

I've just checked all the radiators and I can't find any obvious leaks. All valves are dry and I've felt around all the pipes. I've also checked the overflow pipe and that feels dry but I guess it would do if the leak is tiny enough - I've seen how much water is needed for a 1 bar rise and it's about a mug full!!.

Any ideas what might be causing it? I assume that it isn't a leaky pipe in the walls as I can't see any damp and I would think the pressure would drop more rapidly in that case.

Thanks for any help.

Dave.

may be a leak in the expansion tank or any where else in the actual boiler which is evaporating away as quickly as its leaking

Thanks for that. I'll see how long this refill lasts and then get British Gas out - well, that's what I pay them for.

I haven't tried bleeding the rads but all of them get hot right to the top so I assume that means they don't have air in them. The boiler did gurgle a little for a few seconds when I turned it on after filling.

This forum is great - loads of helpful people around.