K-77 clears existing roots from pipes. Roots are destroyed at the point of entry into pipes. Re-growth is prevented because unlike root cutting machines, K-77 chemically kills roots. Once killed, the dead root "seals off" the point of entry and the root cannot re-grow. Non-corrosive and safe for all types of plumbing. Will work without harming surrounding trees, ground cover or the natural bacteria content in septic tanks and cesspools.