What diameter steel piping is typically used for fill-pipe risers?

The typical diameter for steel piping used for fill-pipe risers in underground storage tank (UST) systems is four inches. This size is favored because it balances the need for efficient flow rates when filling the tank while also maintaining compatibility with the various fittings and equipment used in UST systems. The four-inch diameter allows for a suitable volume of fuel to be delivered quickly during the filling process, which can be essential for operational efficiency.

When considering other typical diameters, while smaller sizes like two inches might be adequate for some applications, they do not provide the same flow capacity necessary for rapid filling. Larger sizes, such as six inches, may be more than what is required, potentially increasing the costs and complexities associated with the installation and operation of the fill-pipe system.