Drainbo Marine & RV Waste Digestant and Drain Cleaner is a biological holding tank treatment formulated for use in all boats, ships, recreational vehicles, and portable restrooms. An environmentally safe, economical and easy-to-use liquid concentrate, Drainbo will penetrate, degrade, and digest biological waste, household grease, and detergents. An All-Natural formula cleans drain lines and digests waste in both the black and gray holding tanks. Eliminate Foul Odors Make Dumping A Breeze Keep Drains Free Flowing Cleans Tank Sensors Adding DRAINBO regularly to your tank will keep your toilets fresh and the waste digested. Adding DRAINBO to the galley or kitchen sink along with the shower or bathroom sink will keep gray water tank fresh and drain lines clean.