I was sent a Moen ioDigital to try out, but haven't installed it yet. I think it takes about 8.5 gallons a minute with four body sprays and one shower head. If I were to add the handheld too, I would be up to 11.0 gallons a minute. Shudder!
That's what I get for going to a nice hotel with body sprays and thinking I would like to have the body spray thing in my home. A few days later Moen called me and offered to send me the kit. I have to be careful of the things I think about.
Thursday I was thinking about this plumber that I hadn't seen in 35 years. I did some work for a contractor that uses him as his regular plumber. The job was a few weeks ago during the cold snap here. I mixed him up with his brother in law, same last name. I wanted to talk to him and tell him that I mixed the two of them up. But then, I hadn't seen the guy in 35 years.
So the next day I go to a supplier, and this plumber at the counter looks and me and asks me if my last name is Love. It was the plumber that I was wanting to talk to that I hadn't seen in 35 years recognizing me! He had changed too much for me to have guessed his name. Stuff like this happens all the time for me.
I would pick up another diverter for the third shower head. And using both the shower side and the tub side is a good idea on the Moentrol.
I would use at least 1/2" copper, and if you use PEX, the 3/4" size.
The Moentrol has a flow rate of 7.5gpm
Good for three 2.5 gpm shower heads.
The PosiTemp has a flow rate of 6.3gpm.
You may want to ask Dana here about heat reclaim. If you have access to the waste line below the shower, you might be able to recover the heat that goes down the drain. I may pick up one of those for my shower.