Do not flush for 6 - 8 hours. The quart of mixture poured into the bowl pushes one quart of water and mixture out of the bowl into the stack. The enzymes and bacteria carried out in the quart leaving the bowl are deposited on the gook coating the pipe. In the following 6 - 8 hours they embed themselves in the gunk so that when the toilet is next flushed they will not be flushed out. The strongest chemical in the World can't climb the side walls of horizontal pipes.
Gravity makes all chemicals run along the bottom.
Nor can chemicals remove much waste in vertical pipes because they flow through so quickly. The bacteria in Bio-Clean are alive and will go anywhere there is food. They will remove the gunk chemicals leave behind. Only roots that are completely dead. Roots enter sewer pipes seeking the rich organic food supplied by the build-up.