Pressure Balance vs. Thermostatic Valves

[Brooke Ward]

We are in the process of renovating a bathroom and replacing the tub/shower with a larger shower-only space. We are planning on having two shower heads (one rain and one hand shower) and would like the option of having both on at the same time. I have been told that we cannot use a pressure balance valve with two separate volume controls because the water pressure would not be sufficient for both shower heads. I've been told that the setup should be a thermostatic temperature control valve with two volume controls.

Any advice or experience using a pressure balance valve for two shower heads? I know that the thermostatic valve provides an added benefit of being able to pre-select the water temperature, but would prefer to go with the less expensive valve if it is an option. We were looking at Grohe, but are open to any suggestions! Thank you in advance for any help and for having such a wonderful discussion board!

[Clayton]

For the last 2 years there's been the request of a large rain-shower and handheld on slide bar or body sprays in ever new home I've plumbed. In the quest to find a brand that I felt was easy to install / repair / get repair parts for / get matching accessories for, I've used Symmons, Delta, Moen, Grohe, Kohler. In conclusion I always use the Moen faucet for this type of shower set up now. I don't recommend against the other brands, just that the moen best fits the needs of me and my customers.
I use the Moentrol pressure ballanced with a 3-way built in diverter. It is available as seen in the pic with a standard shower head and body sprays, but you can also just purchase the control valve seperate and the matching handheld and rain-shower.
The valve is only 1/2" feed, but I've never had any complaints about the pressure. The bottom handle is pulled out for volume control and turned for temp. control, while the top is turned for diverting. The diverter allows you to have one shower running and then as you turn the diverter it will gradually open the second shower head. So both showers can operate at once, continue turning to shut the first shower off and only the second head will be on. With the variable setting you can apply more pressure to either head or make them balanced.
Recommend your pressure be @ or above 40psi with properly sized water lines or you will have very noticable pressure drop with both heads on at the same time. I installed this faucet on a remodel using a water well with 20/40 pressure switch and I had to turn the pressure up to 40/60 for satisfactory results.
I use the Danze 10" shower head with the rubber tips for easy cleaning and the matching Moen handspray.

Good luck,

[Brooke Ward]

Thank you so much for your help. I had previously received a suggestion to use a 3-port diverter (actually someone suggested a 5 port diverter) as a solution but this option seems to require quite a bit more plumbing. As it was explained to me, we would need to loop the two together or provide another pipe to both showe heads in order to have the third option of having both shower heads on (first diversion would be for shower one, second for shower two and third would be connected to both). I have tried to find illustrations online but so far have not stumbled upon anything that seems to depict such a set up. Thus, I went back to researching the valve with two volume controls. Any additional explanation and expertise would be very much appreciated! Thank you!

[Clayton]

The moen 3-way diverter has 3 ports... 1 inlet and 2 outlets. the 2 outlets are "shared" which gives you the ability to run both at the same time with out additional plumbing.

The alternative way of plumbing the shower heads using the 5-port diverter still wouldn't have worked with the extra loop unless you install check valves on the lines, otherwise both would fuction no mater what location the diverter was in and you would still have unused port on the diverter.

As long as you choose a diverter with 2 shared ports then it should work fine. The only time you would need to make a loop would be for a pressure ballance loop on multiple identical body sprays (shower heads) that are to operate at the same time at the same "pressure".

If you want to add other outlets to your shower besides the handheld and the rain-shower, Moen also offers a 5-port diverter that has 2 shared ports.
with it you can operate 2 items together or individually, but the other 2 outlets can only be used individually.

The nice thing about the Moentrol with 3-way diverter is that it is all one unit together. most other systems you have to individually mount the diverter and control bodies and trim them seperatley. Not that big of a deal but it does save on extra fittings and labor installing the valves.

[Brooke Ward]

Thank you for the clarification and helping me through this! Do you happen to know if there are any other manufacturers with a similar valve? Curious if there are others or if the Moentrol is the only way to go. (Would even take your recommendations on systems with separate fittings as long as it does what I'm looking for!) Again, thank you so much!

[let it flow]

This is an old thread to dig up, but the title and discussion fit exactly to my remodel plans and questions. Here is the decision I reached regarding choosing Thermostatic vs Pressure Balanced:
Both types of valves are made with a temperature "memory" feature if there is a seperate on/off control knob. You just leave the temperature knob in the same position. But typical usage is to adjust the temperature as desired for each time in the shower. My wife likes to get some steam sauna effects going so she turns it really hot. I like it very warm if I've been outdoors on a chilly day, or need to relax some muscle aches. I like it cooler if I just finished a sweaty workout, or if the wife is out of town and the "urge" strikes.
My water heater is a 50 gallon size and holds a good reserve of hot water to last thru a shower. I barely notice any temperature change as the heater tank is continuously topped off with cold water, even if the shower in the 2nd bath is also being used. But if the dishwasher or laundry or lawn sprinklers kick on, I do notice a very sudden and uncomfortable change in temperature. The manufacturers of thermostatic valves never say how long it takes to readjust for the temperature change due to pressure steps, but I suspect it is long enough to be noticed. This is because the temperature sensing element has thermal mass which must be changed, then the expansion/contraction (tiny force) of that sensor must be "geared" or leveraged to drive the valve that adjusts hot/cold water flow (big force). This tiny force can overcome the big force if it has time to work on it. (An example is the lawn sprinkler valve. The solenoid by itself is not powerful enough to plug the raw water pressure force. But if the solenoid is used to open a small valve which then fills the chamber to push on the diaphragm that then pushes on the plug to stop the raw water pressure, it does work, but takes several seconds to accomplish.) A pressure balance valve uses the incoming hot and cold raw water pressure to move the mechanism that adjusts flow. There is no time delay for thermal mass to react, and it does not need the time to make leverage work as the raw water pressure has lots of force to quickly move the hot/cold flow valve.
Water pressure in the house is good; on city supply, and there is an adjustable pressure regulator where it enters the house. So there is enough pressure to operate the pressure balance mechanism. A well pump might not build up enough pressure.
I don't know if having 2 shower heads (one rain, one handheld) going at the same time will disrupt the pressure balance valve mechanism because of too low pressure on the pb valve's outlet side.
The extra $100 outlay for a thermostatic valve is not justified, in my opinion and circumstances.

[jadnashua]

I was in a hotel in London where they had thermostatically controlled valves. The pressure was bouncing all over the place as people flushed toilets, etc., and while the volume changed, the temp did not, at least enough to feel. This impressed me enough so when I did my remodeling, I chose the same brand thermostatic valve (a Grohe).

In CA, your seasonal water may not change much, but in NE where I live, the cold water input can change over 30-35 degrees winter to summer. With the thermostatic valve, I can set it to say 105, and it stays at that temp winter or summer. A pressure balanced valve will require a change in the temp control knob where I live AND if you want to maintain the peak scald limit, a change in that internal cam or whatever it takes to adjust it.

[chumbley]

And to further pile on an older thread...

For the first 10 years, our bathroom had a Moen pressure balanced valve. It worked flawlessly. When I remodeled the bath, I went with a Kohler thermostatic valve feeding two separate volume controls for the heads. My thought being that it would be an improvement from the Moen pressure balanced valve. It wasn't. I found the thermostatic valve did not react as quickly as the pressure balancing valve did. So while there was never any cause for concern or scalding risks, you did feel temperatures swings that were never felt with the balanced valve. And my hope of "set it and forget it" temperatures didn't pan out either, as I found myself always tweaking up the temp towards the end of the shower as I got more used to the heat. It was, however, nice to just hit the volume control and know that when I got in it would be at a reasonably close temperature...

Bottom line - next time I'm either going pressure balanced or doing enough research to ensure the valve reacts quickly to supply changes. The Kohler was disappointing.

[hj]

A pressure balanced valve has NOTHING to do with whether you have adequate pressure for both heads. It merely balances the hot and cold pressure so they are equal. Thermostatic or manual temperature adjustment is a "personal preference" and also has NOTHING to do with the performance of the shower heads. Buy the control valve you like and then pipe it properly for the two heads. Some valves have an integral "two device" diverter and others use external diverters. In addition, some thermostatic valves do NOT have an on/off function and then you need individual control valves for each head, NOT a diverter.