The air valve/snifter valve is located at the top of the tank. It may be that a small hose was assembled at the point of installation. Please find the link below to our specs page on the site. If further technical support is required, you can contact us here in the office on 1-877-432-4117.
https://www.wahlwater.com/40-Gallon-Flex-Lite-Retention-Tank-Flexcon-Industries-FLU40EZ-_p_1181.html