Thanks for the helpful reply Poconos. When I said the water is draining back into the well, I meant that I'm fairly sure the water is running up the 8' pipe and then flowing back into well reservoir (repeatedly). I'm pretty sure this is happening because if I disconnect the power to the pump, the water level stays fairly constant...its not outside water constantly seeping in. The water goes up the 8' PVC pipe and underground to a swale about 100' away. The check valve idea makes a lot of sense -- where would one be installed normally? Near the joint at the top of the well?

Secondary question, any idea why sump pumps are put in near pools like this? Is this to maintain the integrity of the pool by not letting the ground get too saturated? I noticed the depth of the pump is just below (and next to) the lowest point of the pool's deep end.

Thanks!