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Say you want to fill a 100 (very small) gallon stock tank in 20 minutes. That's a fill rate of 5 gpm (gallons per minute). A one-inch diameter pipe will have a friction head loss of two (2.0) feet per 100 feet of pipe. If you have 3,000 feet of pipe that is 2.0/100 x 3,000 = 60 feet of head.

The velocity in a one-inch pipe at 5 gpm is 2.0 fps (very low), you could pump at up to 8.0 fps with plastic pipe with no problems (keep it lower for copper). However at 8.0 fps (feet per second) the pressure loss is very high, about 30 feet per 100 feet of pipe, and the pump would not be practical.

You must add to the flow pressure loss an amount for valves and fittings (assume one gate valve for shut off, one check valve to keep the prime and one float valve to control the level in the tank = est 100 feet max equivalent length of pipe - I need to look this up in a book at the office, and 100 feet equivalent length is a good estimate, though a system with lots of valves and fittings could be affected by this added item - use caution). Therefore, add another 100 feet equiv len pipe x 2.0 feet of head /100 feet of equiv pipe length = 2.0 feet of head.

The total pump head is about, 60 feet + 2.0 feet + the elevation difference between the water surface and the float valve at the tank. Let's say the height difference is 40 feet, then the total head is 102 feet.

You need to balance all these things and get the right size pipe and pump for the flow you want. There are many combinations that will work. You may want to install a bigger pipe, like 1-1/2 inch diameter or 1-1/4, check it all out, and think about what you want. A good farm supply store may be able to give you these technical details, or you can get the flow and pressure drop charts for yourself, if you want to.

Or, just do it, something will work well. Depending on the impeller size and pump characteristics, the 1.5 hp may work with a one-inch diameter pipe.

Good Luck

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