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# GPM Calculation

## GPM Calculation

#1
05-17-06, 07:42 AM
Member
Join Date: Dec 2004
Location: MN
Posts: 5
GPM Calculation

Hello All,
How do you calculate the GPM of a pipe? I'm curious as to the GPM capacity of 20' of 3/4" L copper pipe, at 30 PSI. (I need to replace my well's pressure tank, and I'm trying to figure out if I really need an 80 gallon tank for the 1 HP pump.)

#2
05-17-06, 09:20 AM
Member
Join Date: Nov 2005
Location: North Carolina
Posts: 879
you should be more concerned with the draw down desired on the storage tank. a small tank requires frequent pump cycles. if your well can handle the flow rate, go with a larger tank.
the flow rate of 3/4" pipe at 30psi is apx 92 gpm according to Goulds pumps tech data.

#3
05-17-06, 12:34 PM
Member
Join Date: Dec 2004
Location: MN
Posts: 5
Dang, I was hoping the pipe would be the limiting factor, so I wouldn't have to worry about how many GPM the pump can push out.

Any easy way of figuring out the pump's GPM without having to pull it up from the well?

I have a feeling I'm going to have to buy the 86 gallon tank. \$\$\$! :*( (That's what the old tank is, I thought maybe the previous owner bought larger since they also used it on their farm to fill crop sprayers.)

(Hmm, this reply seems closer to "Wells, Sump Pumps, & Septic Systems" material...)