What size supply line is required for 3 Full Baths. We are on City(St. Louis) water supply.

Will this be a residential or commercial installation? Will the baths be in use at the same time? Any more details to give us? Tom

I would not go smaller than 1" main run with 3/4" branches for each bathroom. Hot water not smaller than 3/4".

Reisdential. Wife, two teens, yes, they will most likely be in use at the same time. We currently have 1 full bath and half bath in basement. The plan is to in$tall a full bath in the first floor and a 2nd floor laundry, the wife was concerned about me lugging the laundry from the basement. I'm sure the half in the basement will become a full.

My area runs a size smaller then Milos but if they're going to be used at the same time I'd go with his sizing. Good luck, tom