Hi Jackson, my overflow box has never lost it's syphon. What I do when I am doing a water change is; I leave the pumps running until the water level in the tank falls below the intake slats in the overflow box. Once the water level falls below I then turn off the pumps, and I do the reverse when filling the tank back up. Once the water level reaches the slats and begins taking in water again I then set the pumps running. I am very happy with my overflow box. I'm even happier with they're prices, and customer service.