The valves all come with 'plaster shields' to aid in making your holes the proper size. Use only one (believe it's always the bottom or tub outlet with all Grohe ¾' bodies.) This ¾' valve serves one shower head (on 'champagne'), five body sprays and one hand-held simultaneously with only slight drop in delivery pressure. Don't get the idea that you can increase flow by using both of the outputs on the mixing valve-it won't work. If using more than 1 body spray on a volume control, I suggest the ¾' version ½' is fine for a single output.

Then use additional loops for any volume control serving more than one output-e.g. Your first loop encompasses all of the volume controls served by that thermostatic mixer. These loops ensure that pressure remains constant at any point in the loop regardless of the volume of water being delivered. The main thing about piping a big shower system is to use pressure-balanced loops just like used in irrigation systems.

The instruction with the rough-in valves contain no piping diagrams, which is what I'm looking for help with. I've already tried the Grohe website, but didn't find it helpful. Even if no one here has ever installed a Grohe valve, I'm hoping that maybe a Wallie can at least refer me to someone who has experience in this type of install, or point me to some other resource. This is a complex install, with a thermostatic mixing valve, four volume controls, a waterfall shower head and multiple body sprays. I'm a plumber who has been asked to install a Grohe shower valve (I've installed a ton of Symmons valves, but never a Grohe). I hate to ask a plumbing question in a heating forum, but figure it's worth a shot. To those who install, service and troubleshoot Grohe Products. The GROHE Installation/Troubleshooting Guide.

Grohe twin ell installation