Bison Pumps Deep Well systems require a screen at the water intake to prevent debris from entering the cylinder and causing damage. If your water has silt at the inlet location, then your situation may require a finer filter device than the standard Cylinder Foot Valve Plastic Screen. Bison Pumps offers a Stainless Steel Silt Screen which is 60 mesh, over two feet long, and designed to keep sand and silt out. This screen can help maintain your Bison Pump System.