GrohFlex Universal Rough-In System

We are on the cusp of another bathroom renovation however we've had to temporarily delay the project until we complete our due diligence. Our prior Grohe reno was completed in 2015 and while we are elated with the 2015 project we are in dismay Grohe no longer has "all brass built-in supply shutoffs. The newest Grohe 35601 is a step back over the 35026 and while you can order supply shutoffs for the 35601000 they appear now to be made of plastic. Exacerbating matters is many municipalities especially here in NYC require bath fixture shutoffs unless you like upsetting tenants in your condominium or co-op when you have to shut down water "in the building" to perform maintenance. Moreover, the added cost shutoffs for the 35601's are installed on the valve body and NOT in the rough-in box .... what if you need to replace the whole valve body assembly....duh?

Makes the installation so much easier.

This rough-in system is required for many of the Grohe shower mixers. When first opening the box, it looks complicated, but the instructions help you through various installations -- with and without a tub spout, with and without a diverter. Once installed, the center section comes out easily. The outside plastic is sturdy, yet thin enough to easily cut to the correct depth. There was some minor complexity when first turning on the water. There seemed to be a slight clog which was rectified by blowing through the valve. Installed along with Essence Dual Function Thermostatic Valve in StarLight Chrome (Model # 19988001 Internet #206633708).

The Grohflex universal rough-in system is a neat system. It is used for one rough-in system for many types of installations. This makes it easier for upgrades for function and style. The inlets and outlets are 1/2 in. brass.The grohsafe valve mounts in the box with 4 screws and you do not have any water line connections to make to the valve. I think this type of installation is the best way to go.

We got this Grohflex rough-in box as part of the installation of a Grohflex Cosmopolitan shower system. It is pretty easy to use and since we were doing a full bathroom remodel as opposed to a retrofit, I found it pretty easy to frame around the rough in box so that it could be firmly attached to the wood studs. The rough in box has four female brass pipe fittings with 1/2" NPT threads. The left and right pipe inlets are for hot and cold water and which is which is clearly marked on the housing itself - as you're looking at it from the bath, hot is left and cold is on the right side. The top outlet goes to the shower head, and the bottom one goes to the tub faucet. If you don't plan to use a tub faucet, a small flat screw inside the housing allows the outlet to be isolated to prevent leaks. In our case, we were using the Grohflex model 19-881 balance valve with the top of the rough in box connected to a rain shower head in the shower ceiling and the lower outlet connected to the flexi-hose mounted on the wall. The rough in box is compatible with hot/cold water from pressurized storage heaters, thermally or hydraulically controlled instant hot water heaters however it cannot be used with un-pressurised/displacement style storage heaters so it pays to confirm which type of water heating system you have before you start. The instructions that come with the rough in box are pretty clear and tend to focus on how to install the box as opposed to how to install the pressure balance value in the rough in box itself. The latter is described in the balance valve install instructions and involves unscrewing the four screws that hold the white plastic cover and lifting out the cover from the rough in box with a pair of pliers. I used a vise grip to remove ours. The balance valve then locates in the rough in box and is re-attached with the four screws. For finishing, the finished surface of the shower wall needs to end up between the 'Min' and 'Max' areas marked on the white tape on the top and bottom of the box. We calculated our framing depth using our backer board and finish tile. If there is any of the plastic sticking out after the wall has been tiled around the rough in box, you can cut off the excess with a sharp knife. All in all, it is a quality product with good instructions up to the quality level you expect of a Grohe product.

My wife and I run a small property business in Western Pennsylvania. We buy, renovate, rent, and sell homes in our area. I am a PA-registered home improvement contractor and head up our small work crew. We have a good deal of experience in mid-level and luxury kitchen and bath renovation work. I got my start as a renovator in Greece, and am therefore quite familiar with GROHE bathroom fixtures, as they have been for generations perhaps the most-well-known and respected bathroom fixture brands in that country. Let’s say right off the bat that this is Model # 35026000, also known as 35 026 000 GrohFlex. If you’re reading these reviews to confirm that this is indeed the extra part that you’re going to need to install a GROHE shower kit you’ve bought on homedepot.com, check that model number. Yes, this component is of high quality, it’s occasionally difficult but not impossible to install, and it will give you good service. Much of the rest of this review has to do with technical details that are primarily important to installers. One thing about GROHE that installers working with its fixtures for the first time should know is that the brand has been making an aggressive push to capitalize on its formidable European reputation and push into different markets. There have been some hiccups in this process. Behind these hiccups is, I believe, a brand mentality carried over from GROHE’s days of being a traditional German manufacturing company that does things “the European way.” As the brand is trying to keep design and engineering in Germany, there’s not really all that much understanding of how things work in other markets. Occasionally, this shows up in glaring lapses in design -- what would obviously be a great product in Germany is a nightmare to work with here. GROHE is clearly making serious efforts to overcome this problem. The GrohFlex system is a case in point. But...it’s a big company. It’s hard to make all the moving parts move correctly. I was worried that this system would be fatally flawed in some way. It thankfully isn’t. GROHE claims loudly that it designed this valve system specifically for the North American market. One of the things that this means, thankfully, that there is some additional documentation that will help installers understand the system as a whole. Let’s start with that. Here’s the link for an installation video about putting in the cartridge from GROHE America. https://youtu.be/1fo9JLMLWDY Here’s the link for the product brochure: https://www.grohe.com/us/16265/~dp/cdn-files/us/pdf/GrohFlex_Brochure.pdf I put the general product video is in the video link. So you can see from this literature that the GrohFlex will handle five different kinds of configurations and there’s a high-flow cartridge for a luxury shower that just plug into this rough-in. On several other brands, you need to install the high-flow variant of the rough-in to use a high-flow cartridge -- not here. You probably also noticed the cartridges are massive compared with others from American companies like Moen, Delta, and Kohler. I’d like to ask you to take a look at the product brochure, specifically, the photo that shows an installation of this valve into a 2x4 wetwall. If you’ve done this before, try to look at it for a minute and not laugh, I dare you. OK, let’s move on. Take a look at the valve itself. It’s obvious that your simplest installation is going to be into a 2x6 wetwall, with a piece of 2x6 blocking to screw the valve housing into, which is of course best-practice anyway. With this valve, if you’re working with that 2x6 wetwall, you just need to screw in your blocking back against the drywall at the back of the cavity and the measurements for tile come out nicely at the front of the valve. This is because, unlike other systems, you’ve got some serious leeway with setting the depth of this valve. Please take a look at Figure 1, which is a photo of me measuring the full inch and a quarter of leeway you’ve got to get the spacing on the backerboard and the tile right. By comparison with other popular valves, you might have as little as a half-inch. So that’s a good thing, right? Please look at Figure 2, which shows the top outlet of the valve. When it comes to shower valves and especially luxury shower installations, in soldered copper water supply and branch lines do I trust, all others take a number. There are no solder points on this valve, not on the inlets, not on the outlets. If you’re working with copper, and I hope you are, it all goes in with Teflon tape and 1/2 in copper male NPT fittings. That’s not so good, but hey, it’s not a dealbreaker. Trying to heat up all that brass for a solder connection would be a nightmare on a job. Here’s another point: to accommodate the huge cartridges, the valve is very bulky, 6 3/4 inches wide. If you typically put in air chambers at the inlets to arrest water hammer, even if your framing in a bathtub or shower stall was done by someone with brains and you have the valve center dead on the middle of a regular stud bay with, with the valve in place, you will only have about four inches to get those air chamber fittings in. Sure, it’s possible, but it’s going to be tight and you’d better be on the ball with your work. But once you get the assembly done right and you thread in your connections to the water outlets, test the work and find no leaks, oh baby, this thing is IN. This isn’t a thin-walled valve that’s going to fall down and die on you in five, ten, fifteen years. If you take the cover off the outlet and look at the guts of it, it’s astonishingly simple. Please look at Figure 3: There’s just four holes, two in, two out, surrounded by some very heavy brass with cut-off screws operating ball valves on the inlets.. And that means this thing can handle a truly massive amount of water flow as long as the cartridge doesn’t let you down...and GROHE claims their high-flow cartridge in this valve can handle 14 gallons per min at 45 psi. Last point about the cartridge: while this rough-in is made in Mexico, GROHE designs and manufactures their own cartridges in their own facility in Germany. I highly doubt that 1/2 copper pipe can supply 14 gpm at a safe residential water pressure, but hey, it’s always good to know on a luxury shower build that of all things, the rough-in valve isn’t going to let you down. Ultimately, you have to admit these people are smart, but their marketing people...eh, well, you can’t have it all. If GROHE could get a serious installation video up that shows this valve going into a 2x6 wetwall, as it’s obviously designed to do, instead of that silly shot of a pretzel installation into a below-standard 2x4 wetwall, that would go a long way to assuaging the worries of renovation outfits like mine. Because GROHE fixtures in the bathroom certainly sells middle-class and upper-middle-class properties. Final verdict, this is a great system. The GROHE design team got it done. The marketing is a bit misleading, as are some of the DIY shots of this going into a 2x4 wetwall backed by wood, but it’s a superior product for anyone willing to do the job up to accepted standards of quality.

40 year old basement bathroom renovation underway and the new fixture selected boiled down to either American Standard, Kohler, or Grohe. Researched all the forums and plumbing sites and chose Grohe base upon the design of the rough-in box and durability of the Grohe shower/tub fixtures. What is important is all fixtures leak and when they do you need replacement parts and repair kits. Grohe is customer oriented and will give complete valves away to verified owners of Grohe fixtures in the event they no longer stock repair kits. Documented clearly on their Facebook page but more importantly I found only one occurrence of a Grohe shower fixture reporting a shower head drip and this was after 12 years of reliable use....how nice is that?

Worked great! Easy to install.

It was not needed. The web site told me that I needed it, but I did not need it.

Rating provided by a verified purchaser