• Grohe manufacturers the industry's most reliable accurate thermostatic temperature control valves
• Grohe offers a wide variety of shower components that can be configured to any inspiration or whim the homeowner or designer may have.

A. The Valve-- should always be a thermostatic temperature control valve, and preferably a 3/4" thermostat valve. We recommend the Grohe Grohmix 34.419 or the Grohtemp 34.902 which can be used with either Chiara or Talia trim. These valves will flow enough water to satisfy most needs, but critically important, a thermostat valve will contol the temperature automatically as well. Temperature control in a custom shower is much more than a performance consideration, it is a safety consideration. A two handle valve system will flow more water, but without any constant, practical or safe temperature control at all!
Remember, 1/2" supplies plumbed into a 3/4" valve will still effectively increase water flow. (In this situation, a 3/4" valve will not perform at full capacity but will still flow more than a 1/2" valve.) It is not necessary to have 3/4" supplies to use a 3/4" valve, though when this is an option it is preferred.

B. How Many Shower Outlets?-- This is simply a matter of arithmetic. The sum total flow rate of all shower outlets (shower heads, hand showers, or body sprays) combined cannot exceed the maximum flow rate of the valve at the given water pressure (see flow rate chart below.) Exceeding the capacity of the valve will only lower the overall performance of the custom shower, and thereby lower your customer's satisfaction
For example, all Grohe shower products are restricted to a maximum of 2.5 gpm at 80 psi. Five shower outlets would have a flow rate of 12.5 gpm (5 x 2.5 gpm). The Grohtemp 34.902 has a flow rate of 16 gpm at 45 psi. Obviously, this Grohe thermostatic temperature control valve would do the job.

Note 1: Water pressure is a critical factor in a custom shower. Grohe recommends at least 50 psi for a system with 3 or more outlets.

Note 2: If the number of shower outlets desired is more than one valve can accommodate, it will be necessary to use two (or more) themostat valves. When more than one valve is necessary Grohe recommends that water supplies be 1" or larger.
DO NOT "tee" from one set (hot and cold) of 1/2" or 3/4" water supplies to accommodate more than one valve. In this situation each valve should be plumbed directly from the main water supply. Using a "tee" can cause inconsistency in both water flow and temperature within the custom shower system.

Note 3: Whenever designing a custom shower where a well is involved, make sure you know both the flow and pressure capacity of the well/pump system. A pump supplying 10 gpm at 30 psi might be fine for a simple tub/shower, but it's never going to do the job for a 5-head custom shower with a 3/4" thermostat valve. Either you will have to break the homeowner's heart, or upgrade the well pump.

D. Hot Water:-- Remember the bigger the custom shower, the more hot water that will be required. A ten-outlet custom shower is hardly worth the effort and expense if there is nothing but cold water after two to three minutes. A 50 gallon hot water heater will supply a four-outlet custom shower for approximately 8 minutes (assuming shower heads are restricted and all are turned on for the entire duration)...is that enough for your client? For best overall customer satisfaction, we recommend a 100 gallon water heater as a minimum.

E. Volume Controls:-- Custom showers are generally designed with separate on/off (volume) controls for each outlet -- typically, one volume control for the shower head, one for the hand shower, and one for three body sprays. (OOPS! There is no typical in a "custom" shower.)
Volume controls, of course, have their own flow rates. We recommend using 3/4" volume controls throughout the system...Grohe 3/4" volume controls flow 16 gpm at 45 psi. If cost is a concern 1/2" volume controls can be used, however, the flow rate is reduced to 8 gpm at 45 psi. Remember, the combined flow rates of the outlets cannot exceed the volume control flow rate without a reduction in performance.

F. Body Sprays:-- Any configuration of two or more body sprays requires that they be plumbed with a pressure balancing loop (see illustration below). This technique insures that each outlet delivers the same spray volume and temperature.

G. Valve Outlets:-- Grohe thermostatic temperature control valves are designed with two mixed water outlets. In a shower-only system (this includes multiple-head systems), the bottom outlet should be plugged. If a tub filler is part of the system, plug the top outlet and install a twin ell on the diverter tub spout to supply the shower outlets. (A twin ell is not required on some grohe 1/2" thermostat valves.) Using both outlets simultaneously can cause inconsistency in temperature.

A) User height is one of the critical factors in setting the heights of shower outlets in the custom shower...and all users should be taken into account. Children and anyone confined to a wheelchair can be accommodated with a height adjustable hand shower bar.

B) The shower head should be set at a level above the head of the tallest user but not out of reach for shorter users (excluding children). The reasons are simple: taller users should not have to duck or crouch to rinse their hair; shorter users need to be able to reach the shower head so that they can manually adjust the spray pattern of the head and the angle of the water flow.

C) The top-level body spray is normally set at shoulder or back height. It should not spray horizontally into a user's face or ears.

D) The mid-level body spray is normally set at waist or hip level.

E) The lowest-level body spray is normally set at thigh or knee height.

Note: Body sprays, so matter how many are installed, are intended, primarily, to have the entire body covered by water no matter which direction the user faces. Body sprays should be installed on a different plane from the shower head, whether facing it or perpendicular to it, so that the body sprays flow from a different angle than the shower head.

F) The thermostatic temperature control valve should be set at approximately waist height and should be easily accessible.

G) Volume controls (the on/off valves) should be easily accessible to anyone using the shower, ususlly about waist high and slightly above the thermostat valve (depending on piping requirements).

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