The RVB391 sits at the top of Ronco's light-duty B-series, in capacity territory most RV owners never need - and exactly the territory a skid-mounted wash unit, a crew support trailer, or a full-timing rig in dry country does. It is one of the heavier moldings in Ronco's light-duty B-series at 153 pounds, and it exists for one reason: some builds simply have to carry more water than the standard sizes hold.
The construction is the proven Ronco fresh water spec - translucent natural polyethylene, FDA-compliant resin, molded in Tustin, California on tooling the company has run since 1974. The translucent wall gives you a direct visual on level, which is worth more on a large-capacity tank than a small one; misjudging a tank this size by half is a lot of water and a lot of weight to be wrong about. Speaking of which: at 8.34 pounds per gallon, treat the full tank as cargo in your weight budget, not as an accessory.
Fittings are installed per order, spin-welded or threaded at the locations you specify. Print the technical drawing below and mark it up - fill, vent, supply, and any sender ports - then run the fitting planner on this page to finalize. On a tank this central to a build, the drawing-first approach is the difference between a clean install and a weekend of adapters.
If the footprint fights your bay, the RV water tank family and the wider Ronco Plastics catalog hold the alternatives, and the freight estimator gives you the landed logistics picture. OneSource Plastics is an authorized Ronco Plastics dealer.