Our house was built in the mid 70s. Copper pipe laid in the floor and not lined, in some areas very close to the surface. Many houses on the street have rerouted their central heating piping and some have had leaks. We had a Worcester Combi boiler fitted around 3 years ago. A couple of months ago there was a leak in our hallway floor, under parquet floor. The area of the leak was obvious and whilst it damaged one floor, we were able to claim against it with home insurance. Even though this leak has been fixed (piping was visible and dry for a long time) our boiler pressure continues to drop at a rate of around half a bar per 2 hours. A builder and plumber whilst assisting with the leak also witnessed the pressure dropping completely and rapidly when the hot water was tap was run. I saw this as well but it has not happened since. At the time, a Worcester employee suggested it might be the heat exchanger plate however we had a Worcester engineer out who isolated the boiler and tested to see if the pressure would drop. It held for over 4 hours and dropped when he released. His conclusion was that there was a leak in the piping somewhere. There is no visible water in any of the rooms or under the floors. We know will have to reroute the piping after Christmas (although easier said than done getting hold of people at the moment) however want to minimise the amount of damage caused if there is a leak. And be able to prove the issue with the boiler if that is what's at fault. We have very young children so the prospect of going without heating is not a good one but we could probably manage with electric heaters downstairs if the underfloor heating got shut off. Also cost and disruption to the whole house is a factor in dealing with this. Long post I know (thank you if you're still here). My questions are: Given the rate of the drop in pressure and the amount of time this has been going on, would it not be a sure thing that the water would have shown? The first leak was clear as day and the pipes are so close to the surface. Could anything else cause the pressure drop? Any suggestions in finding locating the leak? (I have purchased a Flir One Camera which hasn't really helped but has highlighted damp patches in one wall). Any other thoughts about the boiler or suggestions moving forward also welcome!