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Old 03-03-2010, 06:12 PM   #1
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Fancy-Shower Rough In Question


I'm preparing for a bathroom reno. I have a tub/shower combo. I have a thermostatic mix valve, and a total of 3 volume controls. All have female 1/2npt fittings.

I have a shower head, which will drop from the ceiling.

I also have a handshower and tub filler spout. Both the tub filler and waterway have female 1/2"npt fittings. Unlike many tub fillers, the fitting is located flush with the *base* of the spout. The waterway as well.

Here's my questions:

1) For the mixing valve and volume control valves, how tight do I need to make the connections to ensure they don't leak? I intend to use teflon tape *and* teflon joint compound at each connection.

2) For the tub spout and handshower waterway, they have very little tolerance and only have about 1/2" of thread. So, I have little margin for error on how far the pipe comes out of the finished wall. I plan to mount a brass drop ear in the wall and use a brass-nipple to come out of the finish wall. I figure that I can always remove the brass-nipple (even once the tile is up) and install a longer/shorter one if I had the wrong length. Is this my best plan? Since this is an outlet fitting, how tight do I need to make the threaded connection? What's the minimum number of full turns I should aim for? Is just 2 turns, for example, enough to make it not leak? Can I cut an installed brass-nipple to make it shorter while still keeping the threads usable?

3) For the shower head, I also plan to mount a drop ear in the ceiling. The finished crome arm will screw directly into the drop ear. Is that my best plan? Or should I use copper plus a female 1/2npt fitting to get the joint somewhat flush with the finish wall?

(Whew)

All advice is greatly appreciated.

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Old 03-03-2010, 08:18 PM   #2
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Quote:
Originally Posted by SteveSmith98 View Post
I'm preparing for a bathroom reno. I have a tub/shower combo. I have a thermostatic mix valve, and a total of 3 volume controls. All have female 1/2npt fittings.

I have a shower head, which will drop from the ceiling.

I also have a handshower and tub filler spout. Both the tub filler and waterway have female 1/2"npt fittings. Unlike many tub fillers, the fitting is located flush with the *base* of the spout. The waterway as well.

Here's my questions:

1) For the mixing valve and volume control valves, how tight do I need to make the connections to ensure they don't leak? I intend to use teflon tape *and* teflon joint compound at each connection.

2) For the tub spout and handshower waterway, they have very little tolerance and only have about 1/2" of thread. So, I have little margin for error on how far the pipe comes out of the finished wall. I plan to mount a brass drop ear in the wall and use a brass-nipple to come out of the finish wall. I figure that I can always remove the brass-nipple (even once the tile is up) and install a longer/shorter one if I had the wrong length. Is this my best plan? Since this is an outlet fitting, how tight do I need to make the threaded connection? What's the minimum number of full turns I should aim for? Is just 2 turns, for example, enough to make it not leak? Can I cut an installed brass-nipple to make it shorter while still keeping the threads usable?

3) For the shower head, I also plan to mount a drop ear in the ceiling. The finished crome arm will screw directly into the drop ear. Is that my best plan? Or should I use copper plus a female 1/2npt fitting to get the joint somewhat flush with the finish wall?

(Whew)

All advice is greatly appreciated.
I'm kind of confused what you're installing this stuff in. Fiberglass Tub/shower combo?

For starters, the shower head, yes a drop ear in the ceiling secured to a block will work just fine. We usually mount them so that the front of the drop ear that the nipple screws into is just shy of touching the back of the sheetrock.

In reference to tightness... thats something that comes with experience. I can't really explain how tight. Thats the whole reason we test things before covering them up.

For a tub spout : It depends on the tub spout you get. There are different kinds, some just have an o-ring and set screw, so you can stub out with a piece of copper and male adapter in a drop ear.

For the hand shower, you have to keep in mind that your nipples only come in 1/2" increments... Gauge that depth according to the unit you're installing. Do not cut nipples off. They are tapered. It probably won't work if you cut some of it off.

As for your teflon/joint compound combo, I never do this. Our code didn't use to let us use joint compound as a sealing agent, so i've gotten in the habit of not using it on anything but gas stuff, or if I have a stubborn union.

Outlet fittings : I tighten them the same as I would tighten anything else.
Hope that was everything.

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Old 03-03-2010, 10:27 PM   #3
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Who is the manufacturer? Do they have any installation spec. sheets on their website? For my kitchen Kohler has detailed rough in specs that tell you exactly how far in/out the rough in needs to be in relation to finished wall.
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Old 03-04-2010, 08:41 AM   #4
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Thanks Alan and Dawktah. Some answers:

1) It's not a fiberglass tub/shower thing. It's a standard alcove tub/shower. The tub is acrylic, and I'm tiling the shower surround.

2) NPT Tightness: I guess my problem here is that I'm uncomfortable with screw fittings. I basically assume they all leak. I assume finger-tight isn't good enough, but do I need to really crank them will all my might?

3) Brass-Nipples, I think the 1/2 increments will work fine since the fitting accepts 1/2inch of thread. My concern here is: If I get it wrong, once the finish wall is up will I be able to unscrew the nipple I put in place and install another one? If I have, say, 1/4 or 1/2 inch of threaded brass exposed, will a strap-wrench or vice-grip give me enough grab to loosen and tighten to a leak-proof fit? Should I not bother installing the brass-nipple until AFTER the finish wall goes up?

4) Thanks for confirming my general approach (drop-ears and brass nipples). I'm a little surprised there isn't a more goof-proof system for doing this work.

5) The problem with getting my distances right isn't a lack of manufacturer specs (I have done one better, I have measured off the actual parts). It's that I'm not sure how think the finished wall will be in the end. My finish wall will be 1/2 drywall, + kerdi + 2 layers of thinset + any imperfection in the wall. All this seems to me to mean that my finish wall estimate could be off by, say, 1/4". This means my brass-nipple may have only, say, 1/4" of thread exposed - is that enough thread to make a watertight seal on an outlet fixture?

Thanks a lot guys.
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Old 03-04-2010, 09:03 AM   #5
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I haven't researched this yet, but the thicknesses of the materials should be available (Kerdi) and someone can correct me on this but thickness of mortar is based on the trowel you use? Also specified by Kerdi. Add this up and that will give you wall thickness. The spec sheet from the manufacturer tells you how the fixture has to be seated against the wall/tub etc. Do you have the pdf? This has most of your answers.

Attached is the spec for our kitchen faucet, see page 2 for what I am talking about.

This helps me as I am doing a new tub and fixtures later this year.
Attached Files
File Type: pdf K-6227.pdf (77.9 KB, 67 views)
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Old 03-04-2010, 09:10 AM   #6
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Actually (or at least from what i've been taught in using screw fittings) you only get about 3/8" of thread engagement. 1/4" of thread may be a little short as far as sealing.

Try to get your finished surface within 1/8 and you should be dead on. Worst case you can always braze two male adapters onto a short piece of L copper to get the exact measurement you need.
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Old 03-04-2010, 09:23 AM   #7
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Please do not link to "competing" web-sites

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Old 03-23-2010, 07:23 AM   #8
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So the results are:

Threaded fittings: I was worried about the threaded fittings, and they were my downfall. It took me 12 hours to get everything mounted, soldered, screwed, etc... (I had to do it twice because my mixing valve ended up slightly out of plane and I wanted it to be right). When I did a pressure test, there was a very, very small leak at each of the supply screw-fittings. I figured this meant that the other 8 screwfittings were also likely to leak. Faced with what appeared to be another 12 hours of work, I hired I plumber instead. $600 and 5 hours of plumber time later, my plumbing was in, tub set, drain connected.

Threaded fittings, part 2: The answer to how tight I should have made them is: Really, really tight. Crank them. The plumber said that, for metal fittings, he's only once ever broken a fitting by overtightening it - and he said you basically have to be "angry" at the fitting to tighten it that much.

Brass Nipples: My big concern about the brass nipples was with installing them after the fact. I thought it would be important to get it right BEFORE putting the finish wall up. I didn't know you could buy an Internal-Pipe-Wrench and easily install the thing after-the-fact.

I was right to worry about the thickness variation on the finished wall - it was more than 1/8 thicker than expected because I had to build up the thinset to overcome an irregularity in the wall/room. But, as mentioned above, it doesn't matter because you can size and install the nipple after-the-fact.

The plumber also did a pretty cool thing: He built a bunch of supports using copper pipe as braces, which he hammered into the wall, and then soldered the plumbing he wanted to support onto it...


Last edited by SteveSmith98; 03-23-2010 at 07:27 AM.
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