Fifty-two gallons in a 28" x 23" x 21" block, and the choice of what runs through it left entirely to you: the Ronco Plastics B295 is a dual-purpose marine and RV molding that Ronco finishes either as a fresh water tank or as a gray or black waste holding tank, depending on the fittings you order. The stout, nearly cubic body is the space-efficient way to carry this much capacity, and its flat faces strap down cleanly against a bulkhead or bay wall. Expect 41 lb on the scale empty, and about 434 lb of water inside when full.
The fitting order is where the tank becomes yours. Fresh water service pairs the FDA-grade polyethylene with potable-rated fittings; holding service points the same rugged shell at the dirty work. Either way, Ronco spin-welds or threads each port at the position you mark - so print the drawing below, draw your actual hose runs, and use the on-page fitting planner to settle fill, discharge and vent locations before you buy.
Tustin, California has been home to Ronco Plastics since 1974, and dual-purpose B-series moldings like this are the backbone of the catalog. Cross-shop the boat tanks wall for other 52-gallon footprints, or the RV holding tanks shelf if this one is bound for a coach. OneSource Plastics is an authorized Ronco Plastics dealer.
Technical drawing: download the Ronco Plastics B295 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.