Twenty-two gallons at 28 lb empty: the B337 is a standard-wall marine blank in the size that suits a pocket cruiser or a weekender's second tank. There is a strong case for splitting capacity at this scale - two moderate tanks instead of one big one means redundancy if a fitting fails, better trim options, and hatches you can actually get the tanks through. The B337 is shaped for exactly that role: substantial enough to matter, light enough to wrestle into place solo.
It arrives as a bare molding and leaves Tustin, California with your fittings installed - spin-welded or thread-installed to marks you set. The workflow is the same one Ronco has run since 1974: print the drawing below, plot your fill, vent, and pickup with the fitting planner on this page, and order. For fresh water duty the shell is FDA-compliant polyethylene, safe for potable supply. As a dual-role B-series blank, it converts on paper to a gray or black waste holding tank simply by ordering waste-appropriate fittings instead.
Plan for about 183 lb when full, with flat support under the whole bottom. Neighboring sizes up and down live in the boat tank category; if this is going under an RV floor, cross-shop the fresh moldings in RV water tanks and the waste side in RV holding tanks. The complete range is on the Ronco Plastics hub. OneSource Plastics is an authorized Ronco Plastics dealer.
Technical drawing: download the Ronco Plastics B337 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.
