The B533 is 4.25 inches tall. Not much taller than a closed fist - and inside that sliver, 27 inches long and 13.25 wide, it still keeps 6 gallons. This is the thinnest molding in the marine B-series on our shelf, and it goes where no other tank goes: under floorboards, inside a seat plinth, in the gap a builder left between two structures and never intended anyone to use.
Dual-role, like the whole B-series: order fresh water fittings and it is a potable tank in FDA-approved polyethylene; order waste fittings and it becomes an ultra-low-profile gray tank. With barely over 4 inches of liquid depth, where you put the outlet decides how much of the 6 gallons you can actually pull back out - so treat the layout as part of the purchase. Print the drawing below, mark the low point of the intended mounting, and set the fittings in the on-page planner. Ronco installs them to those marks, spin-welded or threaded.
It ships at 13 lb and weighs about 50 lb full - loads any sound floor takes without reinforcement. Support it flat and fully; even a light tank this thin should not bridge a gap. Molded in Tustin, California, where Ronco has run since 1974.
If you have a little more height to spend, the boat tanks and RV holding tanks categories sort by size; the whole range is on the Ronco Plastics hub. OneSource Plastics is an authorized Ronco Plastics dealer.
Technical drawing: download the Ronco Plastics B533 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.
