How these strainers work: A small amount of water is returned from the discharge side of the pump to the strainer. Inside, two special nozzles spray against the screen, causing it to revolve. Any debris (e.g., algae, aquatic plants, or leaves) attracted to the screen is blasted off every half revolution. Strainers operate in any position, and require only 35 psi to operate. Eliminate Hot Spots These strainers are designed with internal PVC suction tube with smaller holes at the top, (nearer to the pump), and larger holes at the bottom (farther from the pump) to even the draw or suction across the entire height of the cylinder screen. This prevents water from flowing in harder at the top of the screen, which leads to “hot spots.” (Clogging). Our screens utilize the full surface area for extremely consistent through-screen velocity, which maximizes the effectiveness of the cleaning nozzles.