I'm designing a product to accept a 5-gallon water jug. This is the light blue, transparent plastic kind for potable water that you can buy, swap, or fill at grocery stores. I can take measurements of jugs I own, but I'd like to ensure the product will accept any jug conforming to the standard. Does such a standard exist, particularly for the mating surface of the cooler?
I did some searching and did not find a standard. Majority of these bottles are used inverted on a water cooler and seal via the container holding vacuum (like an inverted dog watering dish) so the dimensions are not critical (and likely not held to a tight standard).
I own two different standards of thread on type 5 gallon jugs that I use in a bottom loaded pump style water cooler. Since a hose pumps the water out, the interface is again not critical.
What I would recommend is contacting some large manufacturers and ask them for drawings or critical dimensions. You wont get a response for all of them, but some will be interested in a product being compatible with their bottles. They may also have information on any standard if it exists. If push comes to shove, you may have to ask for a quote on 50,000 bottles annually and require a detailed schematic with the quote. Tricks you learn ;-)