Compression Joints - how tight and which type of olive?

[Terry lambert]

Poly pipe will naturally distort when compressed with an olive far more than a properly made compression with copper, and so ptfe would make sense.

It's not what compression was designed for.

We don't want to turn this into a plastic cowboy thread

 

[gavinda]

If the plaaaaastic is distorting that much then perhaps it's not being used correctly.

 

[Terry lambert]

Personally I don't use compression on plastic, in fact I rarely use plastic at all.

If I have a compression, I will extend a small piece of copper and then connect with a plastic fitting

 

[gavinda]

But would you wrap the copper in ptfe when using the push fit to extend?

 

[Terry lambert]

Don't be silly

 

[Axel]

How many joints have you made?

A fair few, I imagine, and smoked the lot all by himself.

 

[JohnD]

JohnD, you're clearly not a time-served Plumber.

If you imagine I have claimed to be then you are living in a world of fantasy

 

[JohnD]

1) "Nothing" and "limited" are not synonymous

2) I have had plenty of practice of being a DIYer. DIYers are not the same as plumbers, for example in their skill and familiarity at jointing pipes. So they may do better with different techniques. As a DIYer it is very important to me to be able to make a watertight joint that does not leak, and a technique that enables me to achieve that is valuable to me. The same technique may not be valuable to you. But you are not me and you are not a DIY plumber.

 

[LondonChap]

I have seen PTFE in pipework that blocked a pump because all the compression joints were done with PTFE.

 

[JohnD]

do you mean that in some way the tape unwound itself from the olive (which is on the outside of the pipe) and climbed through to the inside of the pipe, travelling against the water pressure?

that's amazing.

one might even say unbelievable

Was it in your own house?

Have you seen tape do the same thing when wrapped round a tapered BSP tail?

 

[LondonChap]

The olives were wound with PTFE when on the pipe and then inserted into the fitting. On tightening some PFTE unwound and ended up in the pipework. Using a proper paste like Jet blue or that liquid PFTE which some here said was good, would just put gook into the pipework and that can be flushed out easily.

 

[JohnD]

nope, still not with you.

you mean the tape was wound round the olive, and somehow unwound itself despite the pressure of the fitting against the olive, and somehow travelled against the water pressure from the dry side of the fitting into the wet side? Did it cut itself off in some way?

 

[Axel]

"Thread sealants such as joint compound (pipe dope or thread seal tape such as PTFE tape) are unnecessary for sealing purposes on compression fitting threads, as it is not the thread that seals the joint but rather the compression of the ferrule between the nut and pipe. However, a small amount of thread sealant (or plumber's grease, light oil, etc.) applied to the threads will provide lubrication to help ensure a smooth, consistent tightening of the compression nut."

http://en.wikipedia.org/wiki/Compression_fitting

 

[JohnD]

I've just read that.

It says "compression fitting threads"

I haven't advocated putting PTFE on the threads of a compression fittting, do you know anyone who has?

 

[Axel]

Cat amongst the pigeons.....They have got that detail wrong. That's the whole fun of it. No government official or scientist has made rule of law or accepted theory on this. Perhaps a religious scholar can enlighten us?