The 57W is the marine workhorse of the middle sizes: 20 gallons at 32 x 16.5 x 10 inches, a footprint drawn for the space under a v-berth or cockpit sole where a boat's water actually lives. Ten inches of height clears most sole framing; the 16.5 inch width sits between typical stringer bays without surgery.
Ronco catalogs it as a Water / Waste Holding Tank, and on a boat that dual role earns its keep. Ordered with fresh-water fittings it is a potable tank in FDA-compliant polyethylene. Ordered with waste fittings it becomes the head's holding tank - same molding, opposite end of the system. Refit yards spec both from one drawing.
Empty it is 18 lb, molded with the heavier wall a hull install deserves; full it carries about 167 lb of water at 8.34 lb per gallon, which should bear on stringers or a glassed-in shelf, never on hull skin alone. The rest of the marine family is under boat tanks, with the same shells doing land duty in the RV water tanks category and RV holding tanks.
Rotomolded in Tustin, California since 1974. Fittings are installed per order - spin-weld or threaded, at your marks: print the drawing below or use the click-to-place fitting planner. OneSource Plastics is an authorized Ronco Plastics dealer.
Technical drawing: download the Ronco Plastics 57W dimensional drawing - print it to plan your install and mark exactly where you want fittings located; Ronco installs spin-weld or threaded fittings to your marked spec.
