Kleen Waste Holding Tank Treatment deodorizes, cleans lines, and breaks down waste and tissue in not only RV but also boats and portable restrooms; effective in blakc and gray tanks. Kleen Waste is a holding tank deoderant that is effective and formaldehyde free. The unique cleaner leaves the holding tank or head clean and smelling like fresh, wild Michigan Cherries. Biodegradable, non-aerosol. Holding tank waste, treated with Bio-Kleen Kleen Waste, can be safely emptied into any dumping station or septic system.