Add a cover to your sump pump system housed inside a sump box. The sump box is also known as a sump pit, sump tank, or pump vault. The 12 in. Square Sump Box Cover is made of high-density polyethylene (HDPE) treated with UV inhibitors, and fits the 12 in. square sump box, riser, and catch basin drain, sold separately. Hassle-free limited lifetime warranty guarantees the NDS product is free from defects—or we’ll replace it. As part of a complete drainage system, the sump box works with a sump pump system to relieve hydrostatic pressure caused by high groundwater near building foundations. Typically placed at a low point underneath the basement floor, the sump collects surrounding groundwater and pumps it out and away from your property.