The Attwood is a submersible non self-priming bilge pump. It has to be submerged in the pond in order to work. The Surflow is a self priming pump meaning it has positive displacement rubber vanes How far is the horizontal distance from pond to cistern. Unless the distance is very short neither pump will work very effectively due to line losses in the 12V wiring. The alternative is to carry the 12V battery down to the pond each time you wish to use it. Generally speaking pumps can push much further than they can pull.At one camp we installed a submerged pump that pushes water up to the cabin for a lift of 30 some feet but that same pump could not suck up lake water as far as 10 feet. The horizontal run from pump to cabin is 700 feet. We replaced the old 1″ polypipe with new 1 1/2″ PVC piping to produce much greater flow and volume.
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