Is it reasonable to use 3/8″ PEX supply lines to all fixtures?
I am planning the plumbing system for my Net-Zero Energy home that is being built to Passive House standards. I will be using PEX tubing with a manifold system using home runs. I designed the house so that the bathrooms and laundry room are centrally located, making the supply runs pretty short. I want to minimize the amount of water and energy being used and low-flow fixtures provide plenty of water for my needs (2.2 gpm at sinks and 2.5 gpm for showers).
Most people seem to be using 1/2″ PEX for supply lines, but that seems to be more water than is necessary for most fixtures. A 3/8″ PEX line would get hot water to the fixture twice as fast and waste half the amount of water in the process. Considering that the fixtures will be low-flow and the braided line leading to sinks is pretty small, would 3/8″ PEX provide enough water? I can’t see it being an issue for the toilets, sinks, dishwasher or clothes washer. But I’m concerned about the shower and tub. Will I be able to get 2.5 gpm through 20 feet of 3/8″ PEX at about 40 psi? I am on a well, so I can increase the pressure of the system if needed.
I don’t believe that a tub’s faucet has any restrictors, so what flow rate can I expect there? I am fine with waiting a few extra minutes for the occasional soak in the tub.
Has anyone tried using 3/8″ PEX supply lines and what has your experience been? I’ve seen 3/8″ manifolds for sale on line, so I don’t think I’m crazy in considering this.
Thanks for any feedback or input.