Eric it would depend on how many gallons per minute your well and pump produced.Also does your well need to recover after extended pumping time? I top off my pond with well water.It is 200 x 80 feet .pumping @ 18 galloms per minute(which in Livermore Ca. is a large well)I have to run my generator for 20 hours strait to get about 4 inches of water in the pond.Hope this helps a bit... Good luck,Kevin