Oatey's drain seal is specially designed to block odors, gases and insects from entering a home or building through the drain while allowing 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.