Combi boiler slowly losing pressure

[WildCard]

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.

 

[ollski]

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

 

[WildCard]

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.