Three gallons. The BOAT13W is the smallest tank in Ronco's marine fresh water line - 17 x 7 x 7 inches, a 6 lb heavy-duty molding sized for the jobs big tanks are wrong for: a dedicated galley or washdown supply, a day tank for a tender, a helm-side drinking water reserve that does not tap the main system. Small dedicated tanks are how thoughtful boats separate their water uses.
Full, it carries about 25 lb - light enough to mount on a bulkhead face or under a console shelf without engineering anything - and the thick marine wall in FDA-compliant potable polyethylene means it will take the same abuse as its hundred-times-larger siblings.
Even at this size, fittings are installed per order at the Tustin, California plant, spin-welded or threaded to your marks, as Ronco has done since 1974. Print the drawing below, choose the faces for fill and outlet, and set them in the on-page fitting planner.
See the rest of the size run under boat tanks, the small end of the coach line at the 3-gallon RV13W, and everything on the Ronco Plastics hub. OneSource Plastics is an authorized Ronco Plastics dealer.