The Ronco Plastics B187 is a 20 gallon molding from Ronco's marine water / waste series, which means the question is not what it is but what you need it to be. Specify potable fittings and it ships as a fresh water tank in FDA-compliant polyethylene; specify waste fittings and it ships as a 20 gallon gray or black holding tank. For refits this flexibility is quietly valuable: the same proven shell solves whichever side of the plumbing diagram is failing.
Ronco has finished tanks this way in Tustin, California since 1974 - fittings installed per order, spin-welded or threaded at the exact locations you mark. Let the duty drive the layout: water service puts the pickup at the drain-dry point and keeps the vent protected; waste service puts the outlet at the absolute bottom with a generous vent run. Print the dimensioned drawing below, mark your build, and confirm it through the fitting planner on this page.
The tank ships at 37 lb and holds about 167 lb of water at capacity - the platform and restraint should be sized for the full number. Fresh-side alternatives are at boat tanks, holding-side context at RV holding tanks, the complete line at the Ronco Plastics hub, and shipping by ZIP at the freight estimator. OneSource Plastics is an authorized Ronco Plastics dealer.
Technical drawing: download the Ronco Plastics B187 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.
