Header tank losing water - something to fix

I think I've mentioned this before: I keep finding the central heating header tank on Jubilee dry. This is after spells of a few weeks' absence from the boat. It has taken about five pints of water/antifreeze to top it up each time, so it's leaking out somewhere.

I have taken advice from Tony Brooks, who suggests checking all the pipework joints, looking for evidence of antifreeze staining on surrounding woodwork. From memory (I'm not on the boat at the moment) most of the pipework is copper. If there are plastic sections, then a special stiffening section should be present where a compression joint is made, to prevent the joint coming loose.

I have not noticed any water in the cabin bilge, so it's a mystery as to where all the water is going.

Another TB suggestion is to pressurise the system to about 10 psi*, and then any leak should be more obvious. As far as I remember, though, the central heating pipe runs are hidden below the floor. Without pulling up the floor - oak strips - how am I to find a leak down there?

All being well, we should be on board in a week's time or so, so I'll make a determined effort to sort this out. This will be helped by the fact that Ally and Ben have started to remove some of their possessions.

*according to TB: Pressurising can be done with specialist equipment, or by screwing a lorry-type tyre valve into the cap of the header tank and using a bicycle pump.