First time post so go easy, ive had an ongoing issue with my boiler loosing pressure, ive had boiker chexked over and they suggest its a fault with pipework, ive checked for ceiling staining and around all radiators however all dry and no obvious signs, weve tried fernox f4 leak sealer still to no avail, boiler pressure will drop every 3-4 days max depending on use, has even needed topping up after 24hrs, we are almost atbthe point of paying a leak detection company to come and check the system over, im concerned they may find nothing, so hoping yiubguys may have some tips i could try, i am an electrician by trade so have a good understanding just wodnering if i may of missed anything, so any advice on how you guys would approach this would be much appreciated