Connecting jets, shower arm direct to pipe

I have some Grohe jets and a shower arm to fit. The drawings which come with them indicate that they should be screwed directly into a pipe-end embedded in the wall. There are no written instructions. Could anybody give me advice on this?
Look at the fittings, the ends could be screwed into a 22mm pipe which had an thread inside, but they could also attach to a 15mm pipe with a standard compression fitting. Connecting to a pipe embedded in the wall would be neat, but would a standard pipe with a thread cut into it be strong enough to hold a heavy shower arm and head without cracking over time. Is there a special fitting required with the thread? Kevin.
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The ones I have (and haven't yet fitted either!) are 1/2" BSP (Brit. Std. Pipe Thread) So is the shower arm, the mixer tap, the divertor valve and the other fittings. The Grohe jets even have a PTFE seal built-in, so no sealing is necessary.
To use, go down to your local plumbers' merchant and look at a selection of BRASS, female BSP fittings - elbows and straight. You can get them with flanges to take screws (per standpipe-type outdoor taps) or without, and compression fittings or 15mm solder couplings on the other end. Use whichever suits the application, but remember that well made joints in the wall are paramount. You'll be tiling over/around them, so repairing leaks is a horrid job. For the nicest finish IMHO (YMMV), set the female fitting so that the rim just breaks the surface of the tile line by 1mm or so. It'll be covered by the surround for the fitting (if the shower head's pipe didn't come with one, it should have done), but being slightly proud of the surface helps stop grout, etc. getting stuck in the thread when you're finishing off the tiling.
------q p-------- | | -- | ---/
(there are limits to ASCII art!)
When you fit the shower head, wrap the pipe _lots_ with PTFE tape (also from PM) in an anti-clockwise direction, as you look at it from the wall's perspective - so that the tape stays in place whilst you wind the pipe into the 1/2" socket. As I said, if you have the same Grohe squirty bits as I bought, PTFE ought to be unnecessary for them.
One final point, pipe thread of most sizes is available in two forms - tapered and straight (parallel sided). I think you want straight for this application - IIRC tapered is usually for cast iron conduit and gas work. Check with the PM - it's what they're there for. If they don't know or are snooty, find another one!
Regards,
Simonm.
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The picture looks like a brass one, but the blurb says iron. Are you sure?
Regards,
Simonm.
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I think they're referring to malleable iron fittings which are standard 1/2'' BSP Female Thread. If the end of the fitting sticks out past the surface of the plaster on the wall, then you can get these fitting with a chrome finish coating which may match better with your shower head.
Would it be possible for you to type in here what they actually say in the instruction booklet ? Just to make sure. :-))
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What instruction booklet? I was referring to the blurb on the Screwfix site (I didn't make that too clear - sorry). The Grohe fittings I have are probably identical to the ones in question, as I don't think they make many variants (of these little jets). They don't come with instructions, neither did the shower head chromed pipe.
My point was that cast iron is possibly not a good choice over brass in this context, because of corrosion, rust stains, etc. Also, most CI fittings are tapered thread, and I think parallel is correct here.
YMMV - please explain if so, as I'm interested too.
Cheers,
Simonm.
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SIMON MUIR, UK INDEPENDENCE PARTY, BRISTOL www.ukip.org
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<snipped>

Not with you at all now. (?) The fitting you have is a Grohe Shower head fitting ? If it is the one that screws to a fitting sticking out the wall, then it will fit to a brass 1/2'' BSP female threaded fitting.
http://www.grohe-ag.de/catalogue/uk/Sinfonia/images/Z2802201.jpg
Or am I getting the story all wrong ?
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SpamTrapSeeSig wrote:

iron. It just means they are compatible with the older iron threads. They are made of brass.
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I didn't read their description as meaning brass.
The thread is either parallel or tapered 1/2" BSP, and fittings are still available in either brass or cast iron with either of these threads.
If Screwfix meant brass I assume they'd say so.
Regards,
Simonm.
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SIMON MUIR, UK INDEPENDENCE PARTY, BRISTOL www.ukip.org
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