Thetfords Tank Blaster is the first 2-in-1 tank cleaner specifically formulated for black/gray water and portable tanks It cleans overnight, then just dump and go. Micro-Foam Action improves the surface contact to vertical walls while the active enzymatic blend blasts crud and attacks tissue, waste, and grease. The dual-action formula cleans lift deposits from tank walls and super concentrated enzymes attack and break down loosened deposits. Formulated safe for RV/Marine tanks, plumbing, seals, and surfaces.