The guest house I'm building has a 1" copper water supply line running to the house. It ultimately splits out to 1/2" PEX to all of the fixtures, via a manifold. My question is: between coming into the house and splitting in the manifold, when does the 1" incoming pipe step-down to a smaller diameter?
I was originally planning on running the 1" all the way to the cold-water manifold. However, all water heaters I've looked at expect 3/4" inlet and outlet and so the hot-water manifold will be 3/4" as well. Indeed, quite a few of the manifolds I've seen (even for cold-water) have a 3/4" inlet.
Finally, if I look at my own home, I see that I have 1" incoming supply, but it immediately transitions to 3/4" for a water softener and is never used as 1" inside of the house.
So what is "Best Practice" here? Do I immediately step-down the 1" supply to 3/4" as soon as it enters the house or do I keep it 1" all the way to the cold-water manifold and just accept that the hot-water manifold will be smaller?