fozzy1

hi i dont know if anybody can help me with a problem i am having.I have a combi boiler central heating system and when the heating is on ,no problem .once the heating is turned off the perssure gauge goes down to about 1/2 a bar,i have bled all the radiators so there is no air in the system so it seems like i have probably got a small leak some where.the problem being all my pipework is either under the floorboards or under the crawl space beneath most floors.this means having to take carpets/ vinyl and floorboards up .is there possibly a rad/weld type fluid that could be fed into the system to sort this problem out ?