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I am working on a small hydroponic flood/drain system (horizontal pipes at 18", 36", 48" and 72" off the floor level). Typically I use a pond pump with 3/4" outflow for my 30" above ground systems. I just don't think I need that big of a pump because I intend to use 1/4" tubing for pump output side.

However, the small pump I'm looking at has 30" max head. Does weight of the water column factor in? Is the head calculated for the standard 1/2" output? I really only need to get 1 GPH out of it at 72".

isherwood
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Zachary
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2 Answers2

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No, it doesn't work that way. A pump will have the same max head pumping into a 1/4" tube or a big pipe. It's not the total weight of water in the pipe, it's the head pressure, which is independent of pipe diameter for a vertical lift.

If this particular pump has struck your fancy, consider multiple pumps performing multiple lifts of less than 30", stacked one atop another.

MTA
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  1. Most pumps will have what is known as a pump curve. This will be a graph with total head on one axis and flow on the other axis. You should be able to get that from the manufacturer website or wherever you are purchasing the pump.

  2. A simplified version of a total head calculation is (total vertical distance pumped up) - (existing vertical column above the pump) + (friction loss) = total head. So some additional notes:

2A. If your total head calculation is exactly 30 inches (30"), just go to the pump curve and figure out your flow. It will probably be pretty low, because the literature says 30 inches (30") max. But that is what the pump curve will be able to tell you.

2B. If you are putting the pump below the pond level, then yes, you get to subtract this from your total head calculation. I believe you are calling this the 'weight of the water column'. You need to use the bottom elevation of the pond to the pump for worst case scenario.

2C. The friction loss will be higher for a 1/4" hose than a 1/2" hose. But unless the discharge hose length is really long, this number should be negligible. There are tables on the internet showing how to calculate this number.

BPowers97
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