Leaking compression joints

[nemo2000]

Probably a much-discussed problem before, in which case apologies, but.....what is the easiest/best way (if any) to fix leaking compression joints?

Whilst renewing the 'innards' of my toilet cistern I also replaced the 15mm isolator valve in the mains-pressure cold supply (old valve had worn and no longer closing properly, also screw-slot b*****d!). There are now very slight leaks on both of the compression joints. I have tightened both - carefully - twice - but I doubt they will go any further. Curiously, the leaks seem to be worse when the cistern is refilling after a flush and water is flowing in the pipework - I would have expected it to be worse from the pressure when the cistern inlet valve was closed.

The installation is such that it is impossible to disassemble the isolater pipework (eg to replace the olives and try again) without first removing the inlet valve in the cistern. Don't want to do that (too often) for fear of damaging the seal around the the bottom of the cistern as well - enough problems already!

If I slacken off the compression nuts, wrapp PTFE tape around it all, then re-tighten, is that likely to work? Again, I don't want to undo those joints if it only makes matters worse.

 

[JohnKay]

Hi nemo2000
Right, compression joints in general - let's start with new clean pipe, and nice new fitting. All that's really needed is to have the pipe ends cut square, and free from burs. Insert fully into the fitting, and tighten for a fully sound joint.
No PTFE, or compounds (it has to be said that us old fashioned types like a little compound on the olive) Certainly NO PTFE on the thread. The seal is only between the pipe, the olive, and the body of the fitting. The nut simply is a means of compressing the olive, and keeping it all together, it has no sealing function.
Over tightening can cause problems, as this will cause the olive to crush the pipe as well,
reducing it's diameter. A common problem when fittings, and valves are being replaced.
Olives can be removed and replaced, although not easy without special tools.

Back to your leaking fittings. I have to suspect over tightening. Messing about with PTFE is not a permanent repair, and could well make things worse. The only correct way is to cut back the pipe, refit the valve with new olives, replace pipe above and get a new rubber washer for the inlet valve. How about a flex, if it doesn't show ?