I have had a new combi-boiler fitted to an existing pipework / radiator system. Obviously the new system operates at higher pressure than the original system. The system loses pressure over a couple of days and cuts the system out. I have had the boiler checked and it is not leaking internally and there are no obvious signs of leakage. It woudl appear that there is a leak from the pipes under the floor. Unfortunately the pipes are set into the concrete floor. As the system is in my Grandmothers house I am reluctant to put her through the disruption of fitting all new pipes. Does anyone know of a solution to detect / mend a leak underfloor, or have any ideas on other options ? Best Regards Nigel