Polyurethane grouts are designed to react with water and expand in place, forming a tight, impermeable, elastomeric seat that immediately stops the flow of water. Polyurethane seals by forming a chemical bond, a mechanical anchor and a compression seal to act as a waterstop. Because field conditions vary, installation techniques for polyurethane grouts also vary. Polyurethane grout can solve many water leakage problems.