Your 39 gallon Elkhart Plastics fresh water tank includes a 1" vent hole but does not come with pre-installed fittings, allowing you to customize the installation. For the 1" vent, you typically need either a 1" threaded tank fitting or a 1" slip grommet fitting. Threaded fittings provide a secure connection and usually require drilling a 1-1/4" or 1-3/8" hole, while slip grommets offer a flexible, watertight seal without threading. Although we currently stock fittings primarily for 1/2", 1-1/2", and 3" sizes, many customers successfully use the Fresh Water Universal Fittings Kit available on our site, which includes various sizes and types suitable for custom installations. For precise compatibility, ensure the fitting matches your tank wall thickness and material. You can view the universal fittings kit and other tank fittings on our website to find the best option needs.