Max Distance Catchment Tank to Pump

[MarkP]

There is pressure loss per foot depending on flow rate and pipe diameter. If there is a lot of pipe after the pump the consequence is lower flow rate and higher energy consumption per gallon pumped. If the long run is before the pump there are the same theoretical losses with the added problem that if the losses are bad enough the pump can begin to cavitate. In addition to using more energy to pump harder, the pump might not pump effectively or might run really rough. Any leaks that let water out slowly will let air in somewhat faster or if the pipe is buried might let dirty ground water in. It would however take a very extreme case to start seeing these effects. Use a large enough suction line before the pump and you avoid these problems or put the pump near the tank and use as small a pressure line as is convenient and pay for the convenience with higher energy costs.

I suppose that keeping the suction line above grade to eliminate any possibility of sucking in dirty water has a safety value that you can't put a dollar value on and I wouldn't be surprised if the codes have something to say on the issue.