First figure out how many cubic inches are in your pipe.
pi (5 in ) ^2 x (80 ft x 12 in / ft ) = 78.54 in^2 x 960 in= 75398.4 in^3
there are .4 us gallons in 100 cubic inches
(75398.4 in^3 / 100 in^3 ) x 0.4 gal = 301.59 gallons
21.76 US gallons of water.
100 feet by 100 feet by one inch equates to 6,233.76 gallons of water.
100 feet of 3-inch pipe holds 36.73 gallons of water.
About 235 gallons of water.
22.44 gallons for each inch of the water's depth.
12,239.9 gallons of water per 3,000 feet.
5.5 gallons per 15 feet of 3-inch pipe.
14.7 gallons of water.
111 gallons of water.
A 72-inch pipe 16 feet long holds up to 3,384.1 US gallons of water.
You would need 2,451 feet of 2-inch pipe for 400 gallons.
6.5 US gallons of water.