[SOLVED] How do you solder a dripping pipe? Solved

No problem with using a good compression joint .... of you want belt & braces, smear threads with LSX

All the threads do is hold the joint together, it's the olive that does the work. Smearing the threads with something is akin to wrapping them with PTFE tape - both are a waste of time.

Used pipe can be nicked, dented etc, on a tiny scale, and gloop can fill those tiny imperfections helping it seal. Olives bend into place but their ability to fill dents is limited.

The seal is NOT on the threads. That just holds the onion in place.

Still no point in putting gloop on the THREADS.

it's the olive that does the sealing, not the thread on a compression fitting

I wasn't talking about putting seal on the threads you fool. Read & comprehend before replying.

What I said.

You are the one that needs to do that.

Indeed.

Only if you make the mistake of assuming that using PTFE on threads is an attempt at making a seal :-)

The reason PTFE on threads *can* be useful is as a dry, mess free, lubricant, allowing tightening with less effort, and no squeaking and groaning as they tighten.

Agreed, but that doesn't mean there's any point in putting anything on the threads ... and I would never put a joint on a damaged pipe.

Yes, that's true. I put a very light smear of jet blue or boss white on the sealing faces of the olive and a little of this invariably ends up on the thread and acts as lube.

If when tightening a compression join it squeaks and groans probably means that the pipes entering the fitting are not truly in line with the fitting bores. Possibly somewhat unavoidable in some circumstances when repairing or modifying and existing installation and lubricating the thread with ptfe tape can make the tightening of the fitting easier.

In the very many years of DIY plumbing I've noticed not all olives are created equally.

Interesting issue yesterday.

After threats from domestic management, I finally got around to checking and turning on the underfloor heating. Fair bit of white deposit around the temperature control valve assembled as part of the distribution manifold.

Supply pipe secured by conventional nut and olive to a threaded sleeve screwed to the male input port on the valve. Whole issue larded up with plumbers paste so I guess the installers struggled to get a seal.

Problem turned out to be a design/manufacturing defect in that the sleeve was too long (or the valve thread too short) to compress an internal sealing washer!

Turning a few mm off the sleeve seems to have done the job.

Please quote any text where TB mentioned threads. He mentioned imperfection in pipes, and "Olives bend into place but their ability to fill dents is limited".

You're slowly getting worse.

I understand that but it looks awful and amateurish. I would rather use a grease or some other lubricant.

I guess in the OP's situation under the floor and out of the way it wouldn't be an eyesore.

Then clean the pipe properly before fitting. If any damage beyond cleaning, cut it back to good.

Tightening them till they groan is the way I'm sure they're tight enough. ;-)

Couldn't do that when changing a valve on a rad. - short pipe out of concrete, so no room for another fitting. I find that a smear of sealant on the thread reduces the friction and aids correct tightness, rather like not letting friction in a thread distort torque spanner use.

In the real world, old pipe is not perfect, tiny nicks & pits are normal, and the job still has to be done. With the addition of a tiny amount of gloop it's a good bit more likely to seal IME - but I'm not a pro plumber.

The threads don't have anything to do with it.

Rod's always been a near 100% time waster.

You joke surely. Or maybe you only work on new builds.