Here is an email I just received,
Hope I don't scare you but I've got a primitive gravity-flow water system (small tank located apprx. 45' above our cabin and shop locations. It creates a static psi of 18 and @ 10gpm(the max we would ask of it) creates 13.5psi. Everybody I talk to is not sure how I should proceed to get the 4gmp(kitchen) and the 6gpm (laundry tub) flows from the faucets because everything these days is engineered to 50psi mains. My wife wants those flows or as close to it as I can!!!
Seems MAYBE that I should travel the 6-10' from my 1 1/4" delivery pipe into the one story, very small buildings to within 2-5' of faucets with 3/4"pipe, then go to 1/2", then put in a ball valve as a cut-off, use a 1/2" braided stainless steel to the bottom of some kind of old fashioned compression-type faucets(like a laundry tray faucet). If I can maintain a 10psi at the faucets it would satisfy us. 5psi would be minimal I think (but I'm guessing).
I have no plumbing experience and I'm lost as how to solve my predicament. Can you offer any advice for us hillbillies in Ky?
There is a chart in Table 6-5 Fixture Unit Table that shows sizing for 30 to 45 psi