By definition, the manway is the opening on the top of the tank used to allow access to the tank interior for inspection and maintenance. In rainwater harvesting, the manway is commonly used as the primary inlet for collecting rain as it flows through the system to the cistern. Manways are the openings or access points to a pressure vessel or storage tank. The number of manways, the size of the manway opening, and the manway style vary from application to application. When using a secondary containment tank, the manway allows for access through the secondary wall into access the primary tank. Above Ground Storage Tanks (AST) and underground tanks differ in many characteristics from structural engineering to access entry points. For access, AST’s most often have at least one MaxAccess™ (manway or bulkhead) on the side panels, and some even have a secondary access point MaxAccess™ XL or XXL on the roof or dome. Either option, and often both, are required in project specifications from the engineer, architect, and designer. These access point have been through the years debated on size and locations on tanks, but the minimum that you usually specify is a 24″ to 30″, and it’s always a good note to point out that depending on the tanks end usage, there may be additional requirements so check first. Additionally refer to officials in your local and state agencies for guidance and direction on the use of confined space requirements and practices.