Fifty-five gallons under 15 inches of height: the B528 spreads its volume across a footprint just over 34 inches long by 28.5 inches wide, so serious capacity fits where a tall tank never could. This is the tank for the boat that needs real endurance - washdown, showers, a live-aboard weekend - out of a bilge or underfloor void.
The B528 is a dual-role B-series molding. Ordered with supply fittings it runs as a fresh water tank, in polyethylene that is FDA approved for potable use; ordered with waste fittings the same blank becomes a high-capacity holding tank. Ronco spin-welds or thread-installs the fittings to the marks you give them, so the tank arrives configured for its role rather than as a puzzle. Fifty-five gallons deserves ten minutes of layout work: print the drawing below, mark supply, vent, and fill where your plumbing actually runs, and confirm it in the on-page fitting planner.
Respect the full weight. The tank ships at 46 lb but holds about 459 lb of water, and a wide shallow tank concentrates none of it - which is exactly why the format works, provided the floor beneath is continuous. Blocking that supports only the corners is how wide tanks fail. Tustin, California molding, from a maker in continuous production since 1974.
Sit it alongside the other large marine moldings in our boat tank category, check delivery cost by ZIP with the freight estimator, or browse the entire line on the Ronco Plastics hub. OneSource Plastics is an authorized Ronco Plastics dealer.
Technical drawing: download the Ronco Plastics B528 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.
