Tee size in efficient flow splitting of main water supply
James most of the Sinks and toilets in your home have 3/8 plumbing many homes are plumbed with 1/2 pipe through the entire house. The places you will see a pressure drop is usually hose bibs, showers and most kitchen faucets have water saving restrictors built into them. It all comes down to how many faucets will you have going at the same time and the size of pipe and distance of the pipe feeding them. If your home is plumbed with 3/4" that's all you need when you split the 1". I state this as I have never plumbed a house with anything larger than 3/4", but do use 1"pipe to feed most houses larger pipe 1-1/4" for over 100' and 1-1/2" for anything over ~150'. With this said I think you would be wasting $ to go bigger than 3/4" T from your 1" main.