See our project on copper compression fitttings. It will not hurt to use PTFE or Boss white/green paste and yes, you can overtighten. Have a practice on a fitting and a piece of pipe first, it will save you worry in the long run.
i always use ptfe. you shouldnt put anything on the thread cos your just making it difficult to tighten. 4 or 5 wraps halfway around the olive and the pipe so that it fits snuggly into the fitting as this is where leaks can spring from. thats my pennys worth
Tighten until the olive just grips the pipe, then tighten again about 1/3 to 2/3 turn. Test for leaks before covering. No need to use ptfe or joint compound.
"If you're using new pipe and new fittings you don't need any jointing compound or PTFE tape.
If you're pipes are going to be sunk into the wall it would be best to use soldered fittings - or preferably and if possible - no fittings at all."
Yup and also if the pipe is in the wall then wrap it well before plastering. Otherwise there is the possibility of corrosion in the future. Insulating the pipe also allows for thermal expansion.
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