- New
15843 is Thetford Drain Valve Lubricant, formulated to lubricate RV holding tank systems and drain valves from the inside. It helps prevent sticky drain valves and seal wear, restores smooth valve operation, and coats plumbing lines for smoother tank evacuation. The water-soluble formula works with both black and grey waste-water tanks and is 100% biodegradable. The product is supplied in a 24 oz bottle.