Flow Rates in Pipes

A guide the flow rates of pipes.

PIPE DIAMETER = NOMINAL TO PEAK FLOW

½” = 5 - 10 GPM

¾” =  10 - 15 GPM

1” =  16 - 30 GPM

1 ¼” =  30 - 35 GPM

1 ½” = 40 - 70 GPM

2” =  65 - 120 GPM

2 ½” =  80 - 170 GPM

3” = 120 - 270 GPM

4” = 250 - 500 GPM

6” =  500 - 1100 GPM

8” =  1000 - 2000 GPM

10” = 1500 - 3000 GPM

Quick Check – Flow Rate

Normal Flow Rate of a Pipe = D2 x 20

(Diameter Squared x 20)