Question
what is the g.p.m. of a 2" pipe at 38psi
what is the g.p.m. of a 1.5"pipe at 38psi
what is the g.p.m. of a 4", and 3" pipe at 2% grade gravity flow
thanks for your help
have a pool that needs to plum to san sewer and want to hook it up to the pump (5hp)
the outlet pipe is a 2" from the pump
i put a 1.5" pipe 200' long but the pressure shot up to 55psi
i may put another 1.5" pipe in and divert some of the pressure but I'm trying to figure out what is the g.p.m. that i need to meet when it was flowing with out the force main hooked up at 38psi with a 2" outlet
i have an option of gravity flow in the sewer system but don't know if it can handle the volume of water at 38psi ;into a 4" pipe

Answer
is the pipe PVC? if so what type of PVC - SCH40, CL200???

Larry I have a minute here - let me give you some basic information to work with:

First as you may know the safeest way to size pipes is based on velocity. Since I do not know all of the particulars of your project I am going to guess that you have PVC CL200 pipe which is a pretty standard type. No matter the pressure at this point - size the pipes like this: no more than 34gpm through a 1.5" pipe, no more than 55gpm through a 2" pipe and no more than 200gpm through a 4" pipe.

Here's the thing too - what model and brand of pump do you have? we can look at the pump curve and figure out what will be going on. Honestly a 5hp pump sounds pretty large for draining a pool unless you have an olympic pool.

Can you draw a diagram and do you have the pump information?

Thank you!