There is a wealth of information available in the original WW2 Army Motors published by the Technical Service Division, Holabird Quartermaster Motor Base, Baltimore, MD The officer who showed it to us said, “Any resemblance to 5-gallon gas cans living or dead, is purely coincidental.” He was talking about the new 5-gallon watercan (Fig. 1) which has just been developed by the Supply Division of the Quartermaster Corps to meet the need for an ideal liquids container. Speaking generally, the new water can looks as much like the 5-gallon gas can as one bald head looks like another and is of especial interest to Motor Transport personnel because it fits the universal gas-can brackets recently standardized for trucks. This makes it as convenient to carry in odd places on trucks as the gas can itself. It also makes it subject to cases of mistaken identity by casual or ignorant observers. Therein lies a warning: The new water can is as completely non-interchangeable in function with the gas can as rubbing alcohol is with drinking water. It’s unsafe to carry water in the gas can, and its unsafe to carry gasoline in the new water can.
Fig. 1 – Make and Ike, they look alike. So do the gas can and the 5-gal. water can.
Fig. 2 – You can tell it from the gas can by the quick-acting, cam-type cap.  The one best way to tell the water can from the gas can is by the mouth. The water can has a big mouth – three and a half inches in diameter – and a quick-acting, cam-type cap (Fig. 2). It does not resemble the screw-in cap on the gas can at all. Why did they ever make the two cans so much alike in the first place? Because the same tools used for making the gas can could be used to make the water can. Saves time, money and critical materials. The wide mouth makes it easy to clean the new can. This is especially important since the new can will not be limited to the carrying of water — it’ll be used to carry all kinds of liquid refreshments: bean soup, lemonade, bean soup, mulligan stew, coffee, borscht……. All cookie has to do to clean the new can is thrust his furry arm down through the wide mouth and swish soapy water around. For complete safety in carrying liquid foods the new can has a “high-baked”, synthetic lining which is not affected by chemicals in foods. For easy dispensing of liquids from the new can, a small plug located in the center of the cap can be knocked out and a spring-type spigot inserted. Where to get a little spring-type spigot, is information that cookie will get from somebody else. Since there has to be a second opening in the can to let in atmospheric pressure in order for the liquid to pour from the spigot, the designers have provided a little, air-intake valve (Fig. 1). Just screw out the little plug as far as it’ll go (it won’t go far, it’s stuck so you won’t lose it) and a little hole through the threads is revealed. This hole leads down through the plug into the can – air is free to rush in and push the liquid out. The new 5-gallon water can is not what you would call a piece of vehicle equipment – that is, not every vehicle will get one. The best way we know of to find out which will and which won’t, is to look an the Tables of Basic Allowances. But the point we wanted to leave with you, is that there is a difference — the new 5-gallon water can is a horse of a different color. Don’t get it mixed up with the gas can. Take a good look at the cap. From Army Motors, Vol 3, page 193. Editor’s Note: The original scan was poor for the photos above. New scans are in the works.