My preferred tub/shower supply-line layout deviates from standard practice. My goal is to do everything "correctly", but I do not have the experience to know when deviating from standard practices is acceptable. So, I decided that I should ask the pros for advice!

Supplies:
1 Grohe Grotherm 1/2" Thermostatic Rough-in Valve (34 122)
2 Grohe 1/2" Volume Control Rough-in Valves (29 273)
1 Hand Shower on sliding bar (with vacuum breaker)
1 Drop Ell
1 NON-diverter tub spout

Desired layout:

shower head on bar
|
|
supplied from drop ell
|
|
supplied from_______
vol cntrl #1
|
|
thermostatic valve
|
|
vol cntrl #2
supplies
|
|
non-diverter tub spout

The Grohe information states that using both outlets on the thermostatic valve simultaneously can cause inconsistency in temperature. It suggests using one outlet and plugging the other. However, in this layout, would it be permissible to use the top outlet to feed the hand shower and the bottom outlet to feed the tub spout? Both outlets would never be used simultaneously. Alternatively, I would have to loop the supply lines to one or the other adding additional 90s.

I need to have a solution that works with these supplies/setup. Solutions which would require purchasing a diverter tub spout or a diverter valve have already been considered and are not preferred.

Thanks for any assistance!

You'll be fine. The only time that would be an issue would be if you had more than one outlet going at once i.e. a shower head and body sprays.

since one outlet is for filling the tub while the other is for showering, i can't think of a reason to use both at once???
as tom says, use both outlets, you'll be fine
BTW, no fancy vacuum breaker needed on the spray hose. the grohe 34-122 has check valves built in.

Thank you for your quick and helpful reply. What a relief! I have been agonizing over the layout. . .



Edited 1 times.

Thank you also for your quick and helpful confirmation. Other than kids "investigating" I also can't think of any reason anyone would use both at once.
RE vacuum breaker: isn't it required on all hand showers on the hose- in case the head falls into a full tub and sucks "dirty water" back into the potable supply?

or do the Grohe check valves meet this requirement?

you will never get any back syphoning thru the grohe valve.

remember the grohe valve is turned on and set to 109 deg F. you never touch it. i believe there is a button to depress so you can get hotter water thru it. this will help getting a nice hot bath.
the volume controls are kept off. you only open whichever function you choose and close it when finished.
you chose a good quality product. the only downside is if the thermostatic cartridge needs replacement, they are expensive. keep the paperwork around because they are tricky to take apart if service is needed.

Again, thanks for sharing your time and expertise. My Grandma taught me to save, buy quality, do it right, and do it once. Thanks for helping me do that. . . I'm sure I'll have more questions later on!