First, figure that "water out" needs to be supplied by "water in".

Can your plumbing supply the volume needed, meaning, is your supply plumbing tubing large enough?

Can your water heater maintain the proper temp for the volume that will be fed simultaneously through three fixtures?

If "yes", then you can run each item off it's own supply valve, which would allow you to run all three fixtures at the same time, PLUS you can custom select a temp for each fixture.

If "no" then you can still do the same as above...but only select one or two fixtures to be running at a time. OR you can have one supply valve and have one or more diverter valves so you can direct the water to the fixture that you desire.

There are possibilities in between what I just wrote as well.

You asked "Do they make one control that does both? I can't fathom how you'd have two controllers - one for temp and one for direction."

They do. Think of your most basic tub/shower valve. A temperature selector which controls on/off flow and temp, as well as a diverter that sends the water to either the shower head up top or the tub outlet down below.

I find it best to not shut off flow with a simple interuptor, an inexpensive "on/off" button.

Mongo

Mongo,
Thanks for your help. I'm just trying to figure this out because our plumber is working this holiday weekend while we're out of town....

Ours is a new construction master bath, so we have no fixed supply lines- he'll be installing new ones, and we have a huge hot water heater, so that isn't a problem either. We wouldn't be running three at the same time-- just two. Either the fixed wall mount or the hand held, with the rainshower at the same time, sometimes.

Can you point me to a webpage that sells an example of what I would need for this operation? I want preferably one controller on the wall to turn the water on and off and direct flow, but perhaps I need two things on the wall- one to turn the water on and off (and control temperature), and another to direct the flow? If I could see an example of what I need, then I can look for one that has the same features/specifications with a look I like.

Thanks!

look at the hansgrohe and grohe websites. Hansgrohe has a very good explanation/diagram of of how theirs works. Basicall they have an all-in-one that controls (a) temp (b) volume and (c) output. You can choose shower, bath, handheld, or a combination of shower and handheld.

Grohe has a slightly different approach, by separating the temp. control and the flow control. It's more expensive that way, but more flexible. Basically you get a temperature control and then a flow control for each output (shower, rain, hand, bath, etc.)

I've installed the Quattro diverter (from Hansgrohe) that heimert wrote about in several bathrooms. It sound like just what you need.

It has three outputs, and you can select two of the three outputs to run simultaneously.

All you'd need is the Quattro valve, a supply valve, the trim kits for each, and the copper to connect it all together.

All you'd need to do s pick out the locations on the wall where you'd like your valve and diverter to be located as well as the outlet locations of your shower heads.

During the rough-in your plumber will only install the valve and diverter bodies and the nipples for the outlets. So you don;t even need the trim kits at this stage.

Mongo

Here's a link to a worksheet at the hansgrohe site.
http://www.hansgrohe-usa.com/guide/ShowerSystem_Worksheets.pdf.

Looks to me like Hansgrohe makes one set of thermobalance valves that just mix water, Ecostat and Ecomax, and another set that mixes and diverts, Thermobalance I, II and III.

Also, you might visit your local plumbing supply and talk to a salesperson and pick up any literature from the various manufacturers they carry. My local supply store had a great "Custom Shower Workbook" for Grohe products, which helped clear up some questions for me.

As I understand Grohe products, their therostatic control valve only mixes the cold and hot inputs and sends the mixed water to a diverter or an on/off/volume control. So, yes, a therostatic control valve only controls the temperature. Their pressure control valve however, does the mixing and will send the output water to an oulet or a diverter. So, with multiple outlets, say 3, as the OP described, you'd still need a separate diverter of on/off/volume controls when using a pressure balance valve.

The Grohe literature recommends using a thermostatic control valve and an on/off/volume control for each head. So, you turn on the water with the thermostatic valve, sending mixed water to all the on/off valves. You then control the flow from each head separately with each on/off valve. In your case then, you'd have one thermostatic control valve and 3 on/off valves. I'm going with this configuration because my handheld head will be next to the seat on the opposite end of the shower from the shower head. The idea is that my wife can sit on the seat, turn on the handheld and rinse her legs after shaving.

Lots of options.

Bill

Thanks for everyone's help on this, I really appreciate it. I've spent HOURS looking at all the different sites, and thanks for pointing me in the direction of the Hansgrohe and Grohe sites- they were helpful once I found the right pages :)

Ultimately, we decided to go with a pressure-balance. Thermostatic would have been nice, but it was a lot of extra cost and didn't seem to provide a lot of extra benefits (since pressure balance also prevent scalding), and we didn't like the idea of having the temp control and then two or three more controls in the shower-- our shower isn't that big!

Thanks everyone!