We just installed the Kohler "Stillness" trim over a Kohler pressure-balanced valve in the guest bath tub shower. In the master bath shower, we're planning to install the same Stillness trim, but for the Kohler thermostatic valve instead. The pressure-balanced valve works as advertised, and I like the minimalist look of the single-lever trim. Although it's not really a problem, I wasn't initially aware that pressure-balanced valves were either "all on" or "all off" (varying the position of the handle merely controls the temperature). Thermostatic valves on the other hand, have two levers: one for temperature, and one for volume (the valve cover trim for the thermostatic valve will have two handles). The benefit is that you only have to set your preferred temperature once. Thereafter, you'll only have to turn the volume control on. That said, the Kohler pressure-balanced valve looks and works great, and there's really nothing "wrong" with it. However, if you want to control volume, or would appreciate the added convenience of a pre-set temperature, then go with the thermostatic valve.

There are several good companies that offer 1/2" thermostatic valves - for your application i would recommend the Hansgrohe Thermo 1 (for your 1 function shower only) and it would be a great choice and will give you the least fluctuation in temperature. There are other 1/2 thermo valves out there, but do require seperate volume controls, so unless you are redoing all of it, i would recommend the first option.

Yes, a long email with the same questions about the thermostat/gas control valve, and I'm waiting to hear back. Not sure how they could help with the questions about plumbing costs, if your response attempts to imply that I should also direct my questions about that to them. I just thought that I might be able to get a head start here while I waited. Just looking for help, but I'm sorry if I've been a bother. This post was edited by MadtownWriter on Mon, Apr 21, 14 at 21:32

The differences are: One volume control plus diverter (depending on which diverter chosen) is you can operate any combination of the three fixtures independently or any combination of any two together, but at the same volume as the control is set to. Advantage, is lower price of material, less rough in work, less openings in shower wall. Disadvantage, more rough in work, less overall control. Having three volume controls will allow each fixture to be controlled independently so you can have all three fixtures on at once and be controlled at any volume setting independent of each other. Advantage, better overall control. Disadvantage, higher price due to one more fixture needed and more rough in work, one more opening in shower wall. In the end, more openings in shower wall can be dealt with easily so it's just a matter of cosmetics. Also the rough in work isn't much more when adding another fixture, therefore it's a minor disadvantage.