Golf course drainage systems use vertical structures, or inlets, made of PVC or HDPE. Inlets collect surface water and direct it into the drainage system. PVC inlets are expensive, preformed structures that connect to drainage pipe without prefabrication. A cheaper and better alternative is HDPE pipe.
Double wall solid HDPE pipe is sold in 12″, 15″, 24″ and 36″ sizes. Inlet covers, or grates, are available for each size. Plastic inlet covers work well for smaller sized pipe. Use ductile iron covers for larger basins. Light-duty street type frame and grates are fine. Measure diameters before purchasing. The frame may not fit into the inlet inside diameter.
Drill 25, 1/4″ holes, 2″ apart, in the HDPE pipe to relieve hydraulic forces. Use hole saws and portable drills to create holes for incoming and outgoing drainage piping. Add 12″ below the pipe invert (bottom of the incoming or out going pipe) to create a sediment basin.Screw on a plate to the bottom of the inlet. HDPE sold in sheets and cut to pipe diameter works fine.
Cut the inlet pipe holes before installation. Measure the distance between the bottom of the excavation at the intersection point. Identify the low point of the containing swale, then add the downward slope to determine the top-of-inlet elevation. Set the pipe, with the inlet cover attached, on a level surface. Measure and cut the pipe invert. Add 12″ down from the pipe invert to determine the bottom of structure.
Install the inlet in 6″ of crushed stone. Add a few inches of stone along the edges. Fill any gaps in the drainage pipe/inlet connection with geofabric. Be sure to install inlets in low areas to insure surface water flow. Construct swales as needed. They don’t need to be visible, only functional.