Are you referring to a thermostatic valve? It has two controls; one for volume, the other for temperature.

Once you find a good temp, leave the temp selector alone and just use the volume knob to turn the water on/off when you use the shower. The valve will give you the same set temp day after day.

Mongo

Here's the one I used. Along with a diverter, an overhead watertile, and a handheld. Didn't feel the need for body sprays, but with this setup I can have the rain shower, handheld, either or both with the same constant temp. (At least in theory. It's all installed, but I'm still a month out of actually moving back upstairs from my basement.)

Here is a link that might be useful: Kohler thermostatic control valve

Not the most attractive gizmo. Where would it be installed? I will most likely have a double showerhead with one head fixed and one feeding a handheld. I'm in a 40 yo building without great water pressure, so I think that valve might be overkill for me. Would it increase my water pressure though?

Thanks Mongoct! I forgot about that since I don't have it now. That should work OK.

My wife and I finally got to use our shower for the first time this past week. I was wondering if it was going to be worth the extra cost for a thermostatic valve, and I have to say "yes", it was. After the first time finding the temperature I liked, now I just turn on the valve and let it come up to my temperature.
I bought a contemporary Danze Parma.

Here is a link that might be useful: Danze Parma

Ummmmm......That's the rough in valve, it's hidden inside the wall like any shower valve. The trim is on the exterior, which is what you see. This is the one I chose. One knob sets the temperature, the other is on/off volume. You really are blonde, aren't you;) (just kidding)

Here is a link that might be useful: Mastershower valve trim

You could check out the Hansgrohe ThermoBalance II or III. I ordered the III to control a fixed showerhead, handheld shower, and bathtub spout. (The II would be if there's no tub.)

What I liked about this control was that it was a temperature control, volume control, and diverter all in one. Fewer knobs on the wall. :-)

The link is for the valve trim - you'd get the matching type of rough-in valve. The trim comes in a lot of different styles.

Here is a link that might be useful: Hansgrohe ThermoBalance III

I was just being facetious! See, I know big words too...LOL! I knew it went somewhere hidden but didn't know where. Plumbing isn't my strong point. You turn a knob and water comes out! All I need to know!

What's the diff between these gadgets and setting the temp knobs the way you want, and just turning the water on and off as was suggested?

Would these help increase lower water pressure?

These are what Mongo suggested. There are ones from many different manufacturers. The thermostatic valve part is what controls the amount of hot & cold water that goes to the shower head. It keep the temperature at whatever you set it at. You need a volume control to turn the water on and off and control the amount. The one that Charlikin referenced has the temp,volume & diverter built into one knob (note the three levers) while the one I have has a separate knob for temp and volume, and another separate one for the diverter.
I don't think they would do anything for your water pressure. But it wouldn't be any worse either.
Glad you saw the humor, BTW, sometimes a playful joke can come off wrong when you read it:)

Yes, you're right. I just reread Momgos post. I was thinking of what's in my mom's shower. There are regular knobs to adjust the water temp, and then another knob that turns the water on and off. I was thinking you could leave the knobs on the temp setting you want, and then just turn the water on and off. Maybe they do have one of these installed and I don't know. The shower is about 35 yo. Did they have this then?

If this is what I need, I'm definitely getting it. I feel like the three bears every morning. First it's too hot, then it's too cold...

Just imagine if they created one with more than one preset for a couple or family.

What's nice about a thermostatic valve is it keeps the water temperature the same even if what's coming up through the pipes keeps changing. I don't know about your building, but in mine the water temperature keeps changing while I'm showering and I'm constantly having to fiddle with the hot and cold knobs. It will be SO luxurious to just set the temp to what I want and then just enjoy my shower!!

Once I decided I wanted this valve, it was a bit of an education to figure out what controls you needed with different brands to make it all work. Just a single showerhead and tub spout would have been easier, but introducing the extra showerhead (handshower) to the equation upped the ante a bit. Most of the brands would have required four knobs on the wall: one for temperature, and one volume control each for fixed showerhead, handshower, and tub spout. Or maybe substitute a diverter type control for one or two of those volume controls. Still a lot of knobs on a small wall over the head of the tub.

I liked the Hansgrohe because it was only one (largish) control on the wall. They make good showerheads, too.

Blondelle,

With your addition of low water pressure being a problem, a thermostatic valve would be the better choice for you.

Look about halfway down this thread for a pressure balanced versus thermostatic valve yak-fest that I posted a while ago.

Mongo