The B355 is a plank of a tank: 53.5 inches long, 16.75 wide, and just 6 inches tall, holding 21 gallons in the kind of space that exists along a keelson, beside a stringer, or under the floor channel of a van. Shapes like this do not compete with box tanks - they rescue capacity from voids that would otherwise stay empty. If you have four and a half feet of run and six inches of depth anywhere in your build, this molding just made it tankage.
Dual-role, like the rest of the B-series: fresh water fittings make it an FDA-compliant potable molding, waste fittings make the identical shell a slim gray or black holding tank. On a tank this long, port placement is the whole game - a pickup at the wrong end can strand water on a trim angle - so Ronco's build-to-order process earns its keep. Print the drawing below, mark every port with the on-page fitting planner, and each fitting is spin-welded or thread-installed to your spec in Tustin, California, as the plant has done since 1974.
The blank ships at 81 lb - the heavy wall is what lets a shape this long stay stiff - and holds about 175 lb of water when full, spread thin along its length. Support it continuously; a plank tank bridging two blocks will sag. More long-and-low shapes live in boat tanks and RV water tanks, and the maker's whole catalog is on the Ronco Plastics hub. OneSource Plastics is an authorized Ronco Plastics dealer.
Technical drawing: download the Ronco Plastics B355 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.
