I have successfully used compression joints for a long time. The odd one has leaked after installation, but has been made watertight either by a little extra tightening (I tend to undertighten at first) or a wrapping of PTFE tape.
I have just replaced 2 basins and used 4 flexible chrome connectors, each with a compression joint to connect to the existing pipework. 1 is watertight (Hot low pressure), but 3 (2 high pressure cold, 1 hot)continue to weep slightly, despite extra tightening, a wrapping of PTFE tape. (I even tried a smear of Boss Supergreen PTFE pipe jointing compound - No joy.)
Any suggestions to stop this weeping before I stop crying(and weeping!!) and rip it all out and go back to good old copper pipe, bends and standard compression fittings.
The method I use for compression is ensure pipe fully pushed into fitting, do it up, take it apart, make sure the olive is tight on the pipe. Do it up again.
Where did you put the PTFE? On the thread or on the olive. The only place its necessary at all is on the olive which does the work. Practically I haven't used it on compression fittings for about 4 years.
To me the answer is tighten them up a bit more.
Where did you put your service valves? I find that you have to get the flexi very square to the end of the vv otherwise the rubber washer doesn't mate exactly with the vv and it leaks via the centre. Could that be your problem?
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!