This highly effective urinal deodorizer blocks and prevents sewer gas odors from entering restrooms through waterless urinals. Waterless Urinal Sealing Liquid is lighter than urine, allowing heavier urine to automatically flow directly into the waste pipe while the Sealing Liquid remains on the surface functioning as a perfect liquid seal (blocking all drain and sewer odors). As the urinal is used, small amounts of Sealing Liquid will be drained into the waste line and will need to be replenished (usually after 1,500 uses). In a typical school, for example, this amounts to two refills per month.