5 Gallon Bottle Sealing Cap and Collar

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The motivation for this design was from the need to put caps on several 5 gallon water jugs to keep out dust and to prevent spilling water during transport. Having tried several designs from others I decided to create my own since many didn't fit correctly, would constantly break, or didn't seal tight enough to prevent leaks. Why the square cap? To prevent it from rolling under the car when at a filling station when it inevitably gets dropped. The ring washer is optional, it just keeps the collar from coming off too easily, but still makes it easy enough to remove the whole thing when putting the bottle on a water dispenser. If you wish to make your own cap, the collar the threads use an ISO Metric profile 76 mm diameter cylinder, M76x6 thread, Class 6H with a Right Handed thread. To get the cap water tight I purchased some 1/8 inch food grade silicone gasket material and some food grade silicone adhesive. Using the gasket template and a hobby knife cut the around the outer edge, the secured the center of the gasket to the center ring of the cap. The outer edge of the gasket is loose and allowed to flex as the center part of the cap pushes into the bottle hole.