Hi, we have a waterfall in our pool that runs off a Hayward Flow Max II pump. Tried to turn the waterfall on today and nothing. Went out there to check the pump, and it had just about 2 inches of water in it. The pump was on and it sounded like it was running. I could see just a little water movement in the window. Turned everything off and stuck a hose in there, ran it for 30 minutes. Not sure if it should have filled up, but it didn't. Put the cover back on, started it, could see a little water movement and then it just dropped down to 1-2" of water. Pool is almost 3 years old. Any suggestions on what I can check?