Oatey's Drain Seal is specially designed to block odours, gases, and insects from entering a home or building through the drain while allowing a continuous flow of water. This situation is most common in infrequently used drains where the p-trap can dry out and lose its seal. The one-way valve is easy to install without tools and gives peace of mind that harmful sewer gases or other elements cannot enter your structure. Oatey products have earned the trust of plumbing professionals for over 100 years.