The B427 is the tank for the basement bay: 105 gallons in a 39 x 26 x 26 inch block, sized for the pass-through storage compartments of larger fifth wheels, toy haulers, and conversion coaches where fresh water capacity is the difference between boondocking for days and hunting hookups. Among Ronco's RV-friendly moldings this is one of the largest single shells.
It comes out of the same dual-role B-series tooling philosophy as the marine tanks: nothing is pre-plumbed, and the shell can serve fresh or waste duty depending on the fittings. Most B427 buyers spec it potable. Print the drawing below, mark where fill, outlet, vent, and level sender should land for your coach's plumbing chase, and Ronco spin-welds or thread-installs to those marks. The on-page fitting planner covers the size choices.
Do the math before you mount it: the blank is 115 lb, but 105 gallons of water is roughly 876 lb, and that mass needs frame-tied support and baffled driving habits - fill for travel or run near empty, not half. Rotomolded in Tustin, California, where Ronco has built tanks since 1974. See the rest of the sizes in the RV water tank category or start at the Ronco Plastics hub. OneSource Plastics is an authorized Ronco Plastics dealer.
Technical drawing: download the Ronco Plastics B427 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.
