The B439 gives you 40 gallons in a shell that ships at just 45 lb - the light-wall end of Ronco's 40 gallon options, tuned for sailboats and cruisers where every pound of fixed weight above the waterline is argued over. Lighter wall does not mean fragile; it means the molding is intended for a protected mounting space rather than a punishing one.
Dual-role, per the B-series pattern: the same shell is a fresh water tank with potable fittings or a gray/black waste holding tank with sanitation fittings. Ronco installs the fittings per order at your marked locations, spin-welded or threaded. Print the drawing below, mark it from your actual hose runs, and use the on-page fitting planner to lock in sizes before you order.
Water is the real weight here: about 334 lb when the 40 gallons is topped off, so the platform and strapping matter far more than the tank's own mass. Rotomolded in Tustin, California, where Ronco has built tanks since 1974. A heavier-walled 40 and other nearby capacities are in the boat tank category; the full line is on the Ronco Plastics hub. OneSource Plastics is an authorized Ronco Plastics dealer.
Technical drawing: download the Ronco Plastics B439 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.
