PTFE plumbers mait etc

[george [dicegeorge]]

I've been swapping hot water copper pipes and olives. Should every joint have PTFE tape and plumbers mait, or should they be metal to metal, only putting in tape if they leak?

[g]

[John]

Clean metal - smooth surfaces - need no other seal. ie Metal to Metal

[dennis]

If done correctly.. metal to metal. if you need to put sealant on there to stop a leak there is a fault and you should fix it not bodge it with sealant.

[Tabby]

Theyre meant to work metal on metal, but too many leaks in practice means I always gloop them now, that works much better. It only takes a surface scratch on the pipe to make the olive system not work bare. Linseed putty's fine for non-potable uses.

NT

[Tim Watts]

I never use tape on a compression joint.

A smear of some suitable compound is a good idea if it's weeping or if you suspect it might.

[A Plumber]

Don't overtighten the nuts, as this will make the olive squash the pipe, then you will never stop it leaking. normally compression joints should be ok metal to metal, but sometimes boss blue or boss white on non potable joints can be applied

[Tim Watts]

Speaking from a DIY non pro prespective:

The first couple I do after a spell off from plumbing, I undo the nut.

If the olive has just started to bite - ie a torch shows a very slight indentation in the pipe right next to the olive, then that is in the right range IME.

As you say, much more and you distort the olive. Much less and the olive doesn't bite and it can feel tight but the next bit of thermal expansion can leave you with a loose fitting.

I prefer brass olives - harder to do up but there's a satisfying creak noise that lets you know you've got it about right. Copper olives on copper are also fine but I find they don't creak and need less welly so I prefer to be consistent if doing a run of joints.

Much harder on chromed pipe I found - rather more welly required than you initially think and brass olives there are a must - copper's too soft.

If you get the fitting into that state of just-bitten then IME you're guaranteed no serious leaks and most of the time you get a dry joint. A few will weep *very slowly* (moreso chrome IME again) then it's just a case of inching them up bit at a time just until they stop.

Micro weeping (where it looks dry, but is mysteriously damp an hour later) usually cures itself as the minerals in the escaping water clag up the scratch it's getting through. I had one of those - on a chromed elbow where the action of doing up one side distrubed the other side slightly. I got it down to about a drip a day and left it - cured itself after a few days and has been dry ever since. Didn;'t want to risk over tightening for the sake of it for the reasons given by the PP.

[John]

Whatever you do - don't think that applying anything to the threads will help. The threads are not part of the sealing - they are there to pull the joint together and close up the olive.

[george [dicegeorge]]

ooops!

thanks [g]

[Doctor Drivel]

Plumbers Mate is not for threads. On compression joints use a smear of LSX. Compression joints on plastic pipe need PTFE wrapped around the olive.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "dennis@home" saying something like:

In theoryland, Denboi.

[dennis]

Shh don't tell mine, they have been without anything for 30 years!

[Doctor Drivel]

You have no experience of pipework. If the fitting is made to tight tolerances and the pipe is also and no marks on fitting, olive and pipe then it can seal with LSX.

Otherwise use it!

[Tabby]

True that the threads dont provide a water seal, but in the case of a knackered olive and none in stock you can simply fill the nut right up with linseed putty, do it up and the result is watertight. As the nut is done up the putty gets squeezedaround the olive with enough force to do the job.

NT

[F Murtz]

Tape is only for threads never on compression fittings or threads associated with compression fittings. there are some liquids or pastes which can be used sparingly on suspect compression fittings.

[The Medway Handyman]

I often run a turn of PTFE around the thread on a compression fitting simply make it easier to do up. Lubricant, not sealant.

[F Murtz]

One of the problems with that is any subsequent person working on that would jump to the conclusion that a non tradesman had worked on it.

[John]

If you need a lubricant then surely a smear of grease or oil would be better and wouldn't leave a trace so that people would think you had been incompetent.

[The Medway Handyman]

What makes you think that? And why should I be bothered?

[The Medway Handyman]

PTFE is a far better lubricant than oil or grease. Maybe you could explain why the use of PTFE is incompetent?