The 81H turns a corner. Where most holding tanks are rectangles, this 62-gallon molding is drawn as an L, letting it occupy the dead space beside a wheel well or wrap the back of a step - underfloor real estate that a straight tank leaves empty. For a coach that needs big black-water capacity without giving up a straight bay, the L is often the only way to get there.
It is also the heaviest blank in this size class: 128 lb empty, which tells you how much polyethylene Ronco puts into the wall. Loaded, the tank carries about 517 lb of waste water, and an L-shape splits that mass across two legs - so frame both legs, not just the long one, and let structure take the weight rather than the plumbing.
Ronco has molded these in Tustin, California since 1974, and every one ships with fittings installed per order: spin-weld or threaded, located to your marks. Print the drawing below, mark where the outlet and vent go - or use the on-page fitting planner - and it arrives ready to plumb. If a rectangle does fit your bay, compare the 5H at 40 gallons or the 37H at 36 gallons, and browse everything else in RV holding tanks or on the Ronco Plastics hub. OneSource Plastics is an authorized Ronco Plastics dealer.
Technical drawing: download the Ronco Plastics 81H 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.
