If you arent having to fill the pond back up with water each time, and its a concrete pond with a liner over the concrete, my guess would be theres a leak on the water fall area. Pump on is pumping water to top of water fall and water is leaking under the liner. Lifting the liner and pump up. And pump off the water is finding its way back to above the liner. When the liner is rising up then you would imagine a decent amount of water is being displaced. Can you tell much difference in water level? / are you losing any water?
Feel like one of those "I'd have to see it to really appreciate what is happening"
Feel like one of those "I'd have to see it to really appreciate what is happening"