NDS FWBP24 Black Bottom Panel for Flo-Well Stormwater Dry Well System prevents soil erosion under the dry well and provides a solid, stable base when adding a pump into the tank to send water to another location. Made of high-density polyethylene (HDPE) treated with UV inhibitors. Hassle-free limited lifetime warranty guarantees the NDS product is free from defects, or we’ll replace it. The Flo-Well Dry Well System collects, temporarily stores, and slowly releases excess water into the ground. Unlike traditional dry wells which require filling a hole with heavy stone and gravel, the Flo-Well system only needs a small amount of gravel at the base of the tank to prevent scouring. The gravel-free interior provides 2-1/2 times more holding capacity than comparable-sized gravel dry wells.