Most fixture manufacturers make thermostatic valves that do just one thing -- control the mix of hot and cold water at a temperature that you select. Turning the handle on a thermostatic valve doesn't turn the water off and on, it simply selects the temperature setting.

In addition to the thermostatic valve, you need a volume control valve for each emitter (shower head/body sprays/tub filler/handheld/etc.) that you want supplied with temperature controlled water passing through the thermostatic valve. The volume control valve allows you to turn each emitter off and on, and to control the volume of water flowing to each.

You can have as many emitters (and volume control valves) as you want, although the number of emitters you'll be able to have running at any one time will depend on your water pressure, and the size of the water line supplying the thermostatic valve. Generally, if you intend to have more than one emitter on at any given time, you should probably have a 3/4" supply feeding the thermostatic valve. If you plan to have only one emitter on at any one time, you can get by with 1/2" supply line.

The cost of a thermostatically controlled system will vary based on the brand and quality of the fixtures you select, and the number of emitters. Almost all thermostatic systems will cost more than a pressure balanced system with a two or three-way diverter valve. The labour cost to plumb a thermostatic system will be greater, too.

Hope this helps.

James

Thanks James,

That helped a lot.

Instead of having a volume valve for each emitter, can I have a 3 outlet diverter (4 or 5 ports)?? If so would it need one or two inputs?

Debra

Debra,

With a thermostatic valve, you need at least one volume control valve so that you can turn the water on and off. As I explained above, the thermostatic valve controls only temperature. Similarly, diverter valves are single purpose, too. They control only which emitter receives the flow, but don't allow you to turn the water off and on.

If you want a single valve to control the flow of water and temperature, you'll need to go with a pressure balanced valve. With a pressure balanced valve you can turn the water off and on, and regulate the temperature. They (at least the single-handle models) don't allow you to adjust volume - they're either on or off.

Diverter valves typically allow you to choose between two or three emitters. Water flows in one port on the diverter, and out of whichever of the other two or three ports that you select.

Use of a diverter will allow only a single emitter to operate at any one time. If you want to operate more than one emitter at a time (say a shower head and body sprays), then you need volume control valves, which will allow you to turn on more than one emitter at a time.

Hope this makes sense.

James

Nice insights James. Do you mind elaborating on why the installation costs for the thermostatic values will cost more. What extra work does the plumber have to do? I'm considering getting these valves as long as the incremental labor costs are not too much.

There are actually many diverters available which allow you to operate more than one emitter at a time. We are using an 8 setting diverter from Danze that will allow us to operate a main showerhead, a rain showerhead, and a series of body sprays. In addition, this same diverter also has a setting that is specifically an "off" setting, thereby acting as the on/off for the shower.
The installation of the diverter and thermostatic valve (not to mention the body sprays) was more expensive then a typical set-up. I'm not sure exactly how much more though.
Good Luck!

Here is a link that might be useful: Danze diverters

We actually went with a Hansgrohe shower set that has the thermostatic control and diverter all in one rough valve. It's a Thermobalance III, and it can do a tub filler or some combo of two other outlets.

We're in the water business and generally try to conserve, so we keep the flow restrictors in all of our faucets. I say that as preface for the fact that the Hansgrohe valve is really just on or off. You can't fine tune the flow, except a little bit in the split between the two shower/handshower/spray outlets.

According to buffalotina on the Bath forum, this means the Hansgrohe isn't a "true" thermostatic valve. Which I think is a load of hooey, but decide for yourself.

It makes for a very clean-looking installation. And I would think it reduces the cost of install somewhat vs. multiple valves.

Some thermostatic valves do not require a separate volume control, Kohler for instance. The main valve is thermstatic and the on/off.

/p