Polymer well casing pipe is a type of pipe made from high-density polyethylene (HDPE) and mineral and polymer additives and is used to line a drilled well to prevent the well walls from collapsing, protect the water source from contaminants, and provide a barrier against sand and gravel. Polymer casing is chosen for its durability, resistance to corrosion and chemicals, and non-conductive properties, making it a good choice for both large and small wells.