SpudFiles

I've seen people use teflon tape in the past, it seems to work fairly well, and would be a good non permanent seal.
What I do, as I've had problems with leaking and blown out compression fittings at around 150 psi is that I tighten the joint by nut by hand, take the nut off, heat the joint and just let some solder flow around the underside of the now slightly compressed olive, clean the whole thing off and bam, wrap the whole thing with some teflon tape or put a small o-ring on the sealing side and put the nut on again and hand tighten. I've safely taken a 22mm compression joint like that one to around 350 psi, no leaks.

They will make a "grinding cutting" noise when being tightened - they do after all work by digging the olive into the copper pipe.

That said, as far as piston valves, I personally prefer to solder the olives in place. It keeps them serviceable, but considerably strengthens their grip on the pipe - an important thing when you're basically talking about a small hammer repeatedly slamming into parts of the launcher.

[quote="Ragnarok"]They will make a "grinding cutting" noise when being tightened - they do after all work by digging the olive into the copper pipe.

I inspected the thread and the cutting noise is the harder male thread cutting the softer brass thread, leaving a nasty burr on the threads the 15mm compression i can glue but the 22mm side of the tee I'm going to be really careful and use Teflon. I may solder the olives.