OT, moved here in Sept. '06 and the following October we had like 20+ inches of rain, it was insane. Had a partly finished and carpeted basement that flooded early in the month (I had to pull the carpet and demo, 60s plywood paneling on nailing strips, it wasn't a big loss). I installed a sump pump in one corner, next big rainstorm that month came and the one sump did nothing other than collect and discharge water I swept to it (that's the draw-down curve @ice1972is referring to, also called radius of influence). I ended up cutting a trench 20 inches deep around the interior perimeter of the basement, lining with filter fabric, installing a perforated 2" PVC pipe, backfilling with crushed stone in the trench, compact, and replaced the concrete that had been cut for the trench. The pipes were pitched to the sump. That seemed to solve the problem.