I'm about to finish the rough plumbing in my shower, wife wants 2 shower heads. I'm fine with it, but what are the specs for the pipe size? Can I buy 2 shower valves with 1/2" inlets or do I need 3/4"? I am running 3/4" PEX to the first valve and plan to reduce to 1/2" at the valve. But I can do whatever is needed to keep good water pressure, including soldering copper at the valve.
* you're going to want to make sure to balance flow*
In order to do that you will want to loop the pipes around back to itself.
If you want to make the primary loop out of three-quarter inch pipe it certainly wouldn't hurt but is probably not necessary unless you have extremely high flow shower heads.
Sorry I tried rotating the image it keeps going upside down
This is an example of the optional valve[4)] https://www.google.com/url?sa=i&source=web&cd=&ved=2ahUKEwiOycnFsPPgAhWFw4MKHSSuDd4QjB16BAgBEAM&url=https%3A%2F%2Fwww.qssupplies.co.uk%2FTaps%2FStop-Valve%2FProduct%2F485.htm&psig=AOvVaw0yBhytq_2amzj_lDQGskPk&ust=1552163162650315