Twenty-one gallons in a 27 lb package makes the Ronco Plastics B490 one of the easiest tanks in the marine line to live with: light enough to install solo, compact enough for genuinely small compartments, and big enough to matter for a weekend crew.
It is a dual-role B-series molding, which means the tank you receive depends on the fittings you order. Fresh water configuration yields a potable tank, the polyethylene food-grade; waste configuration yields a gray or black holding tank. Either way, Ronco spin-welds or threads each fitting per order at your marked locations, so there is no field modification and no warranty-voiding hole saw.
At capacity it holds about 175 lb of water, 8.34 lb per gallon doing its usual arithmetic. Print the dimensioned drawing below, trace your compartment against it, and route every port through the on-page fitting planner to finish the order.
Molded in Tustin, California, where Ronco Plastics has operated since 1974. The dedicated 21 gallon holding tank covers a decided waste role, and the marine tank range brackets this capacity; shipping is priced through the freight cost estimator. OneSource Plastics is an authorized Ronco Plastics dealer.
Technical drawing: download the Ronco Plastics B490 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.
