Six inches of clearance is enough. The Ronco Plastics B304 spreads 9 gallons across a 27" x 15" footprint just 6" tall - a low pan of a tank made for the gap under a berth, a dinette seat base, or a van floor channel. It is a dual-purpose marine and RV molding: order it with fresh water fittings and it is a potable supply tank in FDA-grade polyethylene, or order it for holding duty and it becomes a slim gray or black waste tank for a compact head or galley. The blank is the same; the fittings decide.
Shallow tanks demand precise ports, and Ronco installs every one per order - spin-welded or threaded at the marks you set. Put the outlet at the low corner for your installed pitch, keep the vent at the high end, and the tank will drain to the last useful quart. Print the drawing below, pencil in your plan, and lock it down with the on-page fitting planner. Ship weight is 16 lb; a full load of water runs about 75 lb.
Ronco Plastics has molded these under-floor specials in Tustin, California since 1974. Related low-profile formats fill out our boat tanks and RV holding tanks shelves when the gap you are working with is a different rectangle. OneSource Plastics is an authorized Ronco Plastics dealer.
Technical drawing: download the Ronco Plastics B304 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.
