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Thread: Help with Grohe valve installation

  1. #1
    DIY Junior Member 149256's Avatar
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    Default Help with Grohe valve installation

    I was looking for some advice. My experience level is good DIYer who can do a satisfactory sweat job. I am renovating an alcove tub/shower and installing a Grohe shower arm/head, new valve/trim, and tub spout.

    I am using Grohflex universal rough in box that came with the valve and trim. The box has (4) 1/2" NPT-MIP female threaded ports with "no sweat option." The fit on the sides of the valve is tight so I cant run any straight pipe then 90 down, I have to run a 90 immediately after the vale housing. So I think I have 3 options.

    1. Use copper 1/2" male adapter with nipple and then sweat a copper 90. I am worried that if I tighten the adapter first using tape and dope then sweat the copper 90 I will damage the tape and dope and cause a possible leak in the threads. But if I sweat the 90 first onto the male adapter then how do I make sure the alignment of the 90 will be correct when I tighten down the male adapter?

    2. Use a brass 90 degree dogear. But same situation above with damaging the seal of the threads if I sweat after tightening them.

    3. Use either the copper adapter or brass dogear and then sweat the threaded portion. I have heard you can do this, but is that true? Can you sweat a threaded connection?

    Any thoughts on the above questions? Or how would you plumb the valve? I hate to ask this question, but should I just use shark bites and forget the sweating.

    Also the tub spout that comes with this unit has a 3/4" NPT-FIP screw on fitting even though the valve is 1/2". Where should I make the 1/2 to 3/4 reduction? Right after the valve or close to the backer board? I have to leave 1/2"-11/16" of threaded 3/4" pipe exposed passed the finished exterior.

    Thanks and hope this is not too confusing.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Did you try to see if a pipe would fit inside the rough-in valve? Many of them are dual purpose, screw on a female fitting or solder in the pipe directly.

    Soldering that close to a threaded connection is not going to give you a reliable connection.

    As to the spout, many of the Grohe stuff specifies a twin-el with the tub spout (if the valve doesn't have a diverter in it). Failure to use one when called for can lead to problems. That may change how you want to hook things up.

    Can you make your first connections to the valve THEN mount it in the wall? You really shouldn't solder close to a threaded connection.

    It would be preferable to not use a Sharkbite there, but they are approved for that application. They also cost probably 10x as much as a solder fitting. If you don't prep the pipe end properly, you can damage the O-ring seal, but if done right, they work. Since they will swivel, you have to anchor the rough-in separately, you can't do it on the pipes.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member 149256's Avatar
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    Thanks Jim, It is not an dual purpose valve. The rough in box has threaded female ports so it is not smooth inside. I don't think a twin-el is called for with this valve. The rough in box, which is actually part of the complete valve assembly after installation, has 2 inlet ports and 2 outlet ports already. One outlet port on the top (shower head) and one on the bottom (tub spout.) You can check out the rough in box here: http://www.grohecatalog.com/product/35026-grohflex

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    Forum Admin, Expert Plumber Terry's Avatar
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    With the 1/2" female inputs, you can either use copper male adapters, or PEX fittings.
    This rough can be configured many different ways. If your tub spout is 3/4", it's best to have a 3/4" drop ear and a pipe nipple there. I rough with a galvanized, and at trim I pull that and use a brass nipple. I carry an assortment to choose from.

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    Moderator & Master Plumber hj's Avatar
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    The fact that they show a plug in the top opening and have a 3/4" spout is "suspicious", since that would normally indicate using only one of the openings and a twin elbow at the spout, but if that were the case they would normally furnish it, so I would have to see the actual installation instructions to know for sure. I always solder the threaded connections so I do not have to worry about any leaking threads.
    Licensed residential and commercial plumber

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    DIY Junior Member 149256's Avatar
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    Thanks Terry. From your picture it looks like you used 1/2 male adapters with tape and or pipe dope into the rough in box, is that correct? I would do that but fear that sweating a 90 right after that, with no straight copper between the adapter and 90, will damage the seal in the threads. Also it looks like your running a diverter valve for shower head, hand held, and tub spout. My layout will be more simple with just a shower head and tub spout with pull-up diverter, so I will use the top port for shower and bottom port for tub spout. Does that make sense to you?

    Thanks for the advice on the 3/4" drop ear and using galvanized and switching to brass at trim. Also I am just a DIYer so what are those copper fittings at the top of the hot and cold supply lines? Are the accumulators and are they code now?
    Last edited by 149256; 11-02-2013 at 04:49 AM.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by 149256 View Post
    Also I am just a DIYer so what are those copper fittings at the top of the hot and cold supply lines? Are the accumulators and are they code now?
    They're hammer arresters. If your valve needs them, it will say in the instructions. You can add them. As far as I know, they are only required on things with fast acting solenoid valves, like the washing machine, dish washer, ice maker, etc. Maybe a question for your inspector, but probably not required.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member 149256's Avatar
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    Quote Originally Posted by hj View Post
    I always solder the threaded connections so I do not have to worry about any leaking threads.
    Thanks HJ, so to sweat the threaded connections do you prep them then tighten them all the way and then heat and apply the solder?

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    Moderator & Master Plumber hj's Avatar
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    IF the picture Terry shows is correct, then both top and bottom openings are "full flow" which means you CANNOT use the top one for a shower riser. If the top one is a shower riser and it is installed as per the picture, the flow volume is severely limited because of the restrictor necessary to keep water from exiting the shower when the tub spout is running. We still need the installation pictures or text to tell for sure. Usually the instructions say you CANNOT use both openings, or more specifically, that you cannot use the bottom one for a tub spout, (without the twin ell).
    Licensed residential and commercial plumber

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    DIY Junior Member 149256's Avatar
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    HJ, The kit i ordered said "Grohe GrohFlex Single Function Pressure Balance Trim with control module for shower only or shower/tub with diverter applications. Integrated bypass option for diverter tub spout. 1 axis operation. 6.6-GPM at 45 PSI. Complete with required 35026 universal rough-in box. "

    The directions are weak, which is part of the problem. But I will attach them. From what I can tell since the valve has the integrated bypass option I can use both the top and bottom openings.

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    Last edited by Terry; 11-02-2013 at 10:15 AM.

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