Septic tank risers from Zoeller Co. are intended to allow easy access to tanks to monitor system performance and can be adapted to both new and existing installations. Available in 8-, 24- and 30-inch diameters - the 8-inch is shown here - these septic tank risers are constructed out of non-corrosive and environmentally safe materials. Gas-tight and watertight, Zoeller's septic tank risers also feature a secured lid. Zoeller Co.