One of my properties they i own has a pool and spa thats has a DE filtration system. the spa is attched to the pool an it has a waterfall effect, that when the system runs, the water flows into the pool. Also, the spa is elevated about 2 feet above pool level. My problem is that when the pump is off the spa somehow empties into the pool. but not through the waterfall. I believe the spa drain and the pool main drain are connected. I have two valves. One for the skimmer and one to the pool. I have tried moving these valves but had no luck. Ihave ruled out any leak because when i turn the system on, after about 10 minutes the water level in the spa raises to normal.