Both options have a thermostatic valve. Neither option has a pressure balancing valve (which would integrate volume with temperature).

As I mentioned, the thermostatic valve is the larger round knob (on the option shown in polished chrome) and the handle with the larger lever (on the option shown in satin).

The question is whether to integrate volume control with a diverter (not with a thermostatic valve).

The option shown in polished chrome has two on/off switches for choosing either of two shower heads. Each shower head is either completely off or turned on at full volume. At most, one shower head can be used at a time. The spray is always at full volume.

The option shown in satin finish has a lever handle that integrates volume with a diverter. If the lever points upward (at 12 o'clock) the water is off. Turn clockwise (toward 3 o'clock) to turn on one shower head and keep turning to get to full volume. Turn counter-clockwise (toward 9 o'clock) to turn on the other shower head and keep turning to get to full volume. Again, one shower head can be used at a time. The spray can be full volume or reduced to a drip.

In the bathroom that I have already remodeled, I have three separate controls (thermostatic, diverter, and volume control). If I want to switch from the jet shower head to handheld, I turn the diverter lever without adjusting the volume.

Which option do you think is more intuitive? Easier to use? Is there ever a reason to use the shower at less than full volume (1.8 GPM max). I don't know if the plumbing installation is more complicated with one option or the other.

I would see if there's a showroom where you can try them out. Functionally, I can't think of a reason why you would need to integrate the volume with the diverter--1.8 gpm really isn't much, so you'll likely want it all the way on whenever it's on (and your shower heads will likely have a range of settings anyway). That said, I really didn't like the button-style diverters, so for sure test them out.

We went with temp and volume control knobs, and then a lever-style diverter built into the hand shower (so not on the wall). Similar to your first option.

I like having some control over the volume, specially if one of the shower heads is a handheld and you want to use it to rinse the glass door, but don't want full volume for that.

I use various volumes on the two heads I use. Sometimes I am sitting on my shower chair, working a conditioner through my hair and the water from the hndheld is at a trickle so I can rinse my hands. Or when I am soaping up, I may keep the water on at a trickle or turn it off. Sometimes, I have the rainhead on at half power. I find myself wondering if you live alone. Shaving legs is another time one may want control over the volume. Heaven forbid someone in your house gets into the Curly Girl Method of hair care. One definately needs volume control, then. I figure that if you have one shower that gives you control, that is worth it. I think you may have to mention it to guests, that the direction you turn the control depends on which shower head you want to control, and the further you turn, the more the volume. Is there any marking on the satin finished diverter?

Our shower has no volume control, I've never missed it. Especailly with those low flow heads, when would you ever want to turn them down from an alreadiy minuscule flow?

On/off right on the handheld head might make sense to save water.

I ave a three way diverter and a thermostatic valve with no volume control. I am not sure why I wouid ever need to control the volume.

FWIW I have unnaturally thick waist length hair and have no issues shampooing or rinsing. That is when a hand held comes in very handy (no pun intended) because I can direct the spray right where it needs to be rinsed just like a hair salon does when they are washing. With long hair or even medium length, you shouldn’t be piling hair on top anyway becaise it causes tangles and potential breakage.

Thank you for all the comments. An on/off switch directly on the handheld would not meet CA requirements where there is more than one shower head. The diverter control needs to shut off one head before turning on the other.

I'm concluding that there is a slight preference toward having the diverter integrated with volume control (as in the photo of shower controls with the satin finish) in lieu of no control over volume. Axor is the only brand I found that offers this option, so maybe not a popular choice.

@plan2remodel you can have an on/off switch on the handheld as long as both shower heads can’t operate at the same time. (The lever on the handheld just shifts the flow from the main head to the handheld when operated.) The volume control for the thermostatic valve controls the volume on whichever shower head is in use. We had no issues passing inspection in CA; it’s a pretty standard setup for Kohler/Grohe/etc.

I absolutely cannot stand not being able to control pressure separately from heat. I use a low flow showerhead and have good water pressure in my house. Sometimes the spray is way too aggressive for the task at hand.

SeattleMCM -- No, again, I am not talking about a pressure valve. The thermostatic valve controls temperature only, not volume. And it doesn't matter how much water pressure I have in my house. I am still limited to 1.8 GPM on the shower head.

artemis78: I have not looked at Kohler or Grohe. Maybe this is an option that works with a pressure valve -- which, again, is not what I have in mind. I'm planning on two shower control valves: (1) thermostatic valve and (2) two-way diverter valve integrated with volume. Both Axor and Dornbract offer this option. I think most other brands require three valves for this type of setup: (1) thermostatic, (2) diverter, (3) volume

I installed the Hansgrohe 27185001 Croma Thermostatic Showerpipe 220 whose left-hand control selects shower-head/off/hand-shower and whose right-hand control adjusts the temperature. There is no volume control and, even though the shower head and hand shower are 2.5 gpm, there is no need. I can't imagine that lower-volume 1.8 gpm shower heads and hand showers would need one.

That Hansgrohe Axor stuff appears overpriced to me. You could get the Hansgrohe HG-T201CR Shower System, and ask Build to substitute the Hansgrohe 04733000 1.8 gpm shower head for the included 2.5 gpm one and substitute the Hansgrohe 04752000 1.8 gpm hand shower for the included 2.5 gpm one. Don't forget the rough-in valve.

To be clear, the Kohler and Grohe options are specifically for thermostatic valves. (On a pressure balanced valve, the volume control and temperature are integrated, so it's not an issue.) I can only speak to those two brands since that's what we looked at, but both offer thermostatic and volume control valves that control whichever shower head is in use. Then the diverter is on the handheld shower head itself. (They also offer separate diverter valves that get to the same end, but we didn't want a third handle.) This is an especially good option for CA (where we are located) because we can't have both shower heads running simultaneously anyway, so there's no reason not to use the main volume and temperature controls for the handheld.

wdcruise: Thank you. The links you sent were to Hansgrohe shower heads. My question is about the shower valves, not the shower heads. What did you use for the control valves?

The Hansgrohe has a product-specific valve (scroll down the Build.com page and you'll see it) but we didn't find that one for sale anywhere with CA-compliant shower heads. (It never occurred to me to ask Build.com to switch the shower heads--not sure if that is a thing or not!) We used the Kohler HydroRail, which is very similar, with the Grohe thermostatic and volume control valves. (We just liked the HydroRail feel better than Grohe's equivalent product.)

"What did you use for the control valves?"

The Hansgrohe HG-T201 linked above is a shower system and includes all the components needed except the required Hansgrohe 01850 rough-in valve. I suggested substituting a 1.8 gpm shower head and hand shower for the 2.5 gpm parts.

One shower system component's on/off and volume are controlled by the volume control. Diverters switch the direction of water flow between two or three exits.A thermostatic valve has one lever that controls water temperature, and a second lever that regulates water volume and the on/off switch (volume control valve). With the help of this technology, you can permanently fix the temperature so that it will always be the way you like it when you take a shower.

HU-

I don't want to "permanently fix the temperature." Only one of the three showers in my house is currently working. Not everyone in my household likes the shower water at the same temperature.

The diverter integrated with volume control will work only with two outlets. If I wanted three outlets (e.g.. jet shower head, handheld, and rain head), I would need to have the diverter separated from volume control, as in my primary shower (see photo below). I think Axor, Hansgrohe, and Dornbracht may be the only suppliers available to me that offer a two-way diverter integrated with volume control. With this configuration, I need only two levers -- one for thermostatic control and one for diverter / volume control.

Actually, the wannabe-plumber (GC's friend / "employee") messed up in my primary shower when installing the rough-ins -- I will need to rip out tile and redo to get hot water. It was my designer's idea to swap the tub and shower from their original positions, which landed the shower valves and heads on exterior walls (the shower area is a "bump out."). The architect had proposed a neoangle shower in the primary bathroom -- but that was nixed by the GC and designer.

I don't think the PP literally meant permanently fix the temperature--of course you can change it! But you set the thermostatic temperature control to the point where you personally like it, and if only one person is using the shower, it can just stay at that setting without having to adjust it every shower as you would with a pressure-balanced valve. (I like hot showers, for instance; my 8yo doesn't, but he has learned to turn the lever to the particular point on the dial that is where he likes the temperature.) We like the two-handle setup a lot since we didn't want a separate diverter control, but you should choose whatever works for your own needs.