Making S-unions watertight for a Hansgrohe shower

21 Nov 2004
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United Kingdom
Hi all,
My Hansgrohe mixer shower was supplied with a couple of s-union fixings to connect the mixer to the backplate elbows that I have installed:


back plate elbows



I can see the point of the s-unions in that they allow for discrepancies in the pipework positioning, but they are being a real pain to seal where they screw into the backplate elbows. There is no way of fitting a washer and it looks like you have to rely on loads of PTFE tape on the threads to do all the sealing. Is that how backplate elbows work? Just PTFE tape?

I have done some googling since and have seen a couple of alternative solutions such as this, but these would involve stripping out all the pipework i have laboriously installed.

Anyone had any good experiences with s-unions?


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Never had an s-union leak, but then I don't use PTFE, I find that Loctite 55 seals threads much better. A bit of jointing paste such as Plumb Blue wouldn't go amiss either.

Failing that clean off the chrome on the threads if there is any and use Loxeal 58-11, but you must be accurate if you use that as it's strong stuff and you'll struggle to reposition after it's set
Millions of pipe unions all over The UK are sealed with PTFE tape. That's exactly what its for, sealing threaded joints.

6 clockwise turns of it (viewed from the open end of the pipe), then do it up nice and tight. Not too tight.

Don't think about it, get on and do it man!
heh. ok, ok point taken. Seriously, this is the first time that I've had to use PTFE on it's own (ie, not as a backup seal to a compression fitting or washer). Thing about the s-unions is that for them to do their job of allowing positioning of the mixer, they can't both be screwed in until they are as tight as they go, because that might not be the postion they need to be for the mixer to mount correctly. I've never screwed something in and left it anything other than tight.. guess I just need to get used to it!

thanks for the confirmation.

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Keep adding a bit more PTFE tape until they stop in the right position and are tight. You might have to add quite a few more turns to achieve this.

Each time you add more turns of tape, the union will stop in a different place when fully tight. Just takes a bit of faffing around.
I find that if you have the backplates fixed first then its difficult.

Bit easier to tighten the s connectors first, then get the levels.

I find that if you have the backplates fixed first then its difficult.

Bit easier to tighten the s connectors first, then get the levels.


yeah, it seems so. But that of course does away with the whole point of the s-union. Is there such a thing as a straight union that reduces from 3/4" at the mixer end to 1/2" at the backplate end? It would need to have a flat bit in the middle to get a spanner around. The s-unions are doing nothing for me because I made sure my backplates were in exactly the correct position.

15mm compression × 3/4" Male Iron, like this one would be a straight version, after a fashion, although the thread on the 3/4" bit is unlikely to be as long as on your fitting.

The thread on a 15mm compression fitting is the same as on a 1/2" fitting so this will screw into your backplate elbows, note that the thread on a 22mm compression is not the same as a 3/4" male iron though so you can't just buy a compression reducer, it must be a 15mm compression × 3/4" male iron.

Talk to your local plumbers merchant, they may well be able to get you one in chrome if you prefer, and maybe sort something with a longer 3/4" tail as well.

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