Place the Bio-Drain Cleaner in the urine basin. It contains enzymes that prevent urine salt deposits that may form creating a blockage in the urine drain tube. Five tablets per box. Longevity depends upon use. Please note: we recommend rinsing the urine tube periodically with vinegar or hot water. This will help to keep the urine line clear. Most users do not find need to use the Bio-Drain tablets, but if you find a slowing of the urine draining, we would recommend the enzyme tablet to help keep the lines clear.