Comparing Flow Rates of Faucets

You should be able to plug the pressure values into this site and get some answers.

Good Luck.

Pipe Friction Calculation for Fluid Flow in a Pipe

PEX is 'The Answer' to almost any re-plumbing job according to plumbing pro's I have asked. The PEX should be 3/8" to maintain flowing pressure. Do whichever is easiest as end results are equivalent--but protect the PEX from mechanical damage--do not leave it exposed to hits from mops. vacuums, shoes,etc.

Still can't guess what a pex is. Surely if it is only 3/8" diameter it will introduce too much loss?

GA to Frankston. Here is some info on PEX piping. To specifier, you may want to plumb in as large a diameter piping as possible. With PEX 1/2 inch is 3/8 id and 3/4 is 5/8 id. If you want the very high flows you will likely need something larger than these diameters from your city line or well inlet to the tap. It is not unusual to see housing with 1.25 inch copper headers (or larger) to various locations to minimize pressure drops.

PEX stands for cross-linked polyethylene. Earlier versions of PE pipe/tube without the cross-linked structure tended to fail prematurely. The X improvement seems to have fixed this. PEX is now commonly used for under-pavement snow melting, hydronic heating, and domestic plumbing.

Obviously- if no special materials are in place, the calculation would be that the flow from the 4 gpm faucet would be 4 times square root of (45/20).

BUT- it is very likely that the 4 gpm faucet is flow limited by some type of variable restricter insert and will remain very close to 4 gpm at whatever pressure is applied.

Thanks for all the great answers! I also called a p.e.x. manufacturer and was told that the diameter of the 1/2" p.e.x. shouldn't affect the water flow significantly, especially since we're only moving the sinks about a foot to the right. He also said that the velocity of the p.e.x. is higher that the copper lines, which helps. The main determinant of the flow is the valve in the faucet. Also, the Roman tub faucet with 17 g.p.m. @ 45 psi will fill the tub much faster than the 4 g.p.m. @ 20 psi.

Doesn't this depend upon the shape of the container the water is being delivered into and the position of the nozzle relative to it? After all, if the flowrate is too high and the shape not as desired, the water will leave the vessel and end up outside it....