300-Gallon Holding Tanks Similar to our 250-gallon model, the PolyJohn 300-gallon holding tank is a necessity as a sanitary receptacle for waste for an outdoor rest area where indoor plumbing is not an option. Our functional and discrete holding tanks reassure workers or guests that waste is being stored safely. PolyJohn holding tanks are made of an extremely durable plastic, and easily work with different plumbing configurations to ensure that your rest area remains as clean and uncluttered as possible. Specialized design means that our holding tanks can be used with many of our portable restroom or sink models interchangeably. The 300-gallon capacity allows for maximum waste storage. Features: ?C thick wall construction ideal for bulk waste storage under trailers on job sites ?C No threaded or cemented joints; accepts Fernco rubber couplers and clamps ?C Also available in natural which reveals fluid at-a-glance (required in certain states) Advantages over other alternatives: ?C Discrete appearance ?C Extremely durable construction ?C Works with a variety of plumbing configurations