Fitting Bib tap - thread preparation

[Kevin Brady]

Quick one really - When fitting a 1/2" into a wall plate, do I need to put anything on the thread first (like PTFE), or is this not necessary.

Cheers

Kevin

[David Lang]

I'd always use PTFE tape personally, costs a few pennies and ensures a leak free joint.

Dave

[Grunff]

It's far better to understand the purpose of PTFE in a joint and use it accordingly than to just use it on every joint.

In this case, it's a parallel thread joint, which will require some kind of sealant to make it water tight. PTFE (or alternative) is therefore required.

However, there are many other types of joint where the seal is created in a different way (metal/metal, metal/rubber etc.), and using PTFE in those situations is neither desirable nor recommended.

[Mr Fizzion]

I guess most people wouldn't use it on soldered joints. :-)

Are you saying that it is not appropriate for compression joints?

Mr F.

[Grunff]

[Rob Morley]

But it can be a good quick bodge on a dodgy compression joint, at least until you fix it properly.

[Grunff]

I disagree. If a compression joint is leaking, and further tightening doesn't fix the leak, it is unlikely PTFE will fix it.

Think about how a compression joint is made - the olive is squashed against the pipe and against the two parts of the fitting. The only reason for it to leak is if the pipe, olive or fitting is damaged, or it hasn't been tightened sufficiently.

[Rob Morley]

So you wrap tape over the thread and the olive - with luck that will contain the leak within the fitting.

[Grunff]

Hmmm...

[Rob Morley]

I said it was a bodge :-)

[Alan]

Yes. I have never used (or needed) any form of sealant in a compression joint. If the olives don't seal it then there is something wrong, like grit in it.

Alan.

[David Lang]

I've always used it on compression joints, including high pressure fittings on CDS hydraulic tube @ 200 bar+ and I've never had a leak yet.

Dave

[Kevin Brady]

Thanks for all responses

Ok - PTFE tape on the shopping list for use where a threaded connection ITSELF is making the seal - i.e. Bib tap as per my original post.

Incidently - the Hep20 website suggests using the tape beneath the olive of a compression joint to help lubrication , but not to seal the joint.

Regards

[Grunff]

But why? It just doesn't make sense - that isn't how the fitting works.

[Grunff]

Several people have made this suggestion in the past, but I realy don't like the idea - if you want to lubricate, there are plenty of suitable products for this which won't in any way interfere with the joint.

[Richard Conway]

Me too - but I do often wonder if they would have leaked had I not!

[David Lang]

I know, but with mass produced fittings (probably from China) there are always tolerance issues. PTFE takes up any imperfections in the thread/olive/tube.

The beauty of tape it that it stays there rather tha being wased away.

Dave

[Grunff]

The olive does a pretty good job of that.

Why would you want to replace a metal/metal seal with a metal/PTFE seal?

I just don't get this "use PTFE regardless" approach - I've made hundreds of compression joints without PTFE tape on a single one, and have yet to experience a problem.

[Kevin Brady]

At the risk of a further display of inexperience, doe the PTFE tape around a bib tap thread fitting 'gunk' it up, meaning that I would not then be able to unscrew and refix. It's just that this will govern whether I do this part of the work sooner or later in the list.

Thanks,

[Grunff]

No, you'll be able to unscrew it with no problems.