It feels like I'm asking for the simplest thing ever for my shower.

I want:

1. A shower with both an overhead and a hand unit working at once.
2. One master temp/volume control, where with one handle I can use both the overhead and hand unit, setting temp, etc.
3. \*VERY\* occasionally turn off the overhead (so I can bathe my dog with just the hand unit).

My plumbing supplier has me in the weeds. We're currently looking at the Rohl line of fixtures. Rohl has the following fixtures:

RCT-1 (1/2” PRESSURE BALANCE WITHOUT DIVERTER), which does the single-control volume/temp capable of 6GPM at 60psi. ([images.salsify.com])

R1040R (UNIVERSAL 3/4” VOLUME CONTROL ROUGH VALVE), which is a line shut-off that can let me turn the overhead off. ([images.salsify.com])

Here's the proposed plumbing schematic:

The supplier is saying it won't work because when the overhead line is closed via the volume control, back-pressure will come back to the T, then travel upstream of the T and affect the pressure-balance valve (RCT-1).

Now it's important to note that the line to the hand-held unit will never, EVER be closed. That side of the T will always be open.

How will the back-pressure come back upstream of the T? The flow will always be going into the T and out of the hand-held side. How could pressure go back up.

I mean it will slightly vary the pressure because the flow will be variable, but this is the same as using a single showerhead with variable flow settings, right, should be able to handle it fine as long as there's still a net output to the flow from the pressure balance valve.

Am I missing something here?

(Note: I shower late at night after hockey, usually in the near dark to not wake my wife. I really, really want to have just one control to start/stop my shower and change the temp, which I do regularly during a shower. The overhead shutoff will VERY rarely be used. Only when I'm showering the dog. So really the flow will never change when the RCT-1 is in the ON position. Only very occasionally will the flow rate change, and that will happen before the RCT-1 is turned on.)

Thanks!



Edited 1 times.

The pressure balancer is monitoring the relative hot and cold pressures AHEAD of the valve, NOT the "mixed" pressure after the valve so any "back pressure" is irrelevant.

I think it will work for your stated purposes.

The only downside is this is non typical so when you sell the house eventually a buyer may see this as a defect instead of a feature. "Why can you shut off the overhead shower but not the hand shower? This needs to be fixed as part of the condition of sale!" and of course by then the fix is difficult because it means removing wall tiles and opening the wall cavity.

The simple solution is to install a diverter at the tee, to go to 1 only, 2 only or both.

My understanding is in these situation of multiple devices it's either (a) thermostatic valve with multiple volume controls, or (b) pressure balance with multi-port diverter.



Edited 1 times.

ditto

separate diverter valve with three positions:

A - B - or BOTH A & B

Quote

..... The 3-way shower and tub diverter enables you to change the water flow between handheld showerhead, mounted showerhead, or both at once. .....

Said valve installs IN THE WALL after the mixing valve

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

I have piped hundreds of shower systems the way you diagram shows and have not heard any negative feedback hj is correct the back pressure is not severe on the mixed port

Should work as long as the hand held is not left on and the sprayer is in the off position,,as it can circulate back thru water piping and cause hot water to come out the cold side of another faucet,,,Kitchen sink for example.. The same thing can happen if a slenoid valve malfunctions on a washing machine connection...

the hand held should NOT have an OFF else it could create a cross connection between H and C if the overhead were turned off with the mixer open

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638