This product is a non-acid formulation made for most sewer, vertical and lateral line stoppages. Introduce Main Line Cleaner through a downstairs floor drain, shower, bath tub, or clean out fitting. Drain System should contain as little water as possible. Before using allow backed up water to drain out. It is best to use when facilities are not used for 7 to 8 hours, such as overnight. This product should be used completely in one application. Pour the entire gallon into the drain, and after 8 hours flush with hot water for 5 minutes. If problem persists, a second gallon of Main Line Cleaner may be required.