connections to concealed thermostatic mixer

[MartC]

I've got a mixer/diverter to connect, the inlets are 3/4" bsp and outlets are 1/2" bsp - all female parallel threads as far as I can make out. How best to make these joints? There are machined faces on the mixer sockets, so I expect the intention is to use fibre washers (and I'd also use thread seal) with parallel thread male bsp to copper compression couplers. Ideally I'd like to use an elbow coupler to save space but then if I have to tighten this to pinch the washer I've no control on orientation - so it'd have to be a straight coupler then an elbow after. However, can the washer be left out and thread seal alone used to make the joint with the elbow oriented as required? Something like Fernox water hawk?

I've been warned against using tapered thread male fittings into brass sockets (splitting) and that they should only be used on steel fittings.

It's going to be hidden in a tiled stud wall for (hopefully) many years to come, no leaks esential - whats the longevity of fibre washers, I've heard of leaks developing over time, is there a modern alternative?

Thanks

Martin

[MartC]

Hi Dave, I'm the OP. Harry's suggestion to use tap connectors won't work, as you say, because they are the same gender as the mixer. The females on the mixer are machined in (not captive nuts) and I could use the 'running bsp parallel', but looking at that fitting how are you supposed to seal it? There are no shoulders so either it seals on the thread in some way, or else the sealing faces of the two females it connects must pinch a washer and then you have the orientation problem again!

I guess the basic underlying question is - can you reliably seal parallel threads without using fibre washers, ptfe or thread seal compound?

Martin

[MartC]

Oops, should of course read ..., by using ptfe or thread seal compound?

Martin

[Grimly Curmudgeon]

You'd need to be a gorilla with no sense of tightness. Try one and see for yourself.

Steel fittings on fresh/tanked water are a pitfall waiting to happen anyway, with internal corrosion blocking them up and then falling apart. Steel pipe on heating systems only works because it's de-oxygenated water in there.

[YAPH]

I wrote a bit about installing those on the wiki

[YAPH]

Oops, sorry - just realised you said 'concealed' I saw the 3/4" BSP bit and thought you were referring to bar-type mixers.

[Grimly Curmudgeon]

Yes. Loctite do a thread seal (nothing like the normal threadlok) for exactly that purpose.

[MartC]

This stuff?

very recent, and google shopping gives no hits

or there is 572 and 577 on this page

potable is not metioned for those.

however on that page Rocol foliac GP & PH - cheaper and for potable water.

[Dave Liquorice]

Soory, first day of the kids back at school at getting up early is having it's toll...

supposed to seal it?

Thought you said there was a machine flat face. Maybe I have made a wrong assumption in that flat face being at the bottom of the machined female thread?

Not sure where the sealing faces are... Pop a fibre washer down the mixers female, screw in the "running BSP parallel" and gently nip the washer, then use a tap conector elbow (with free female nut) and fibre washer on the other end of the "running BSP parallel". As the nut is free it'll tighten with the elbow in any orientation.

Not sure I'd trust PTFE or compound on parallel BSP threads, I think they are too loose in toleramce unless you can tighten them against something.

I might be tempted to use a brass taper/parallel double male, with the taper going into the mixer with plenty of PTFE wound the right way around it. No need to seriously screw it in or as you say you may split the female.

[Grimly Curmudgeon]

I do believe that's the very one. I used it a couple of years ago on a shower installation [1] where it would have been impossible to get to the rear after finishing. I had my doubts about it, but since the customer supplied it (and he was quite knowledgeable) I took it at face value and used it. Nothing has leaked and that was 2007.

[1] Sod's law dictated that the only unions available to fit the supplied fittings of the shower meant they had to be parallel fitting.

[Grimly Curmudgeon]

ps. That shower was supplied from a 3bar booster pump.

[Nospam]

Use hemp with a sealing paste, such as Jet Blue. You'll find that the hemp will bind and seal the thread.

Dave

[docholliday93]

If the thread is long enough and there is enough room it may also be worth using a back nut or jam nut to provide additional sealing. Mike

[MartC]

Mine's mains pressure, so that's good to know - thanks