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Tank Top Sump

A generic term for a liquid-tight container installed on top of an underground storage tank designed to house various storage components.

Tank top sumps serve a variety of functions including the containing of leaks from submersible turbine pumps and piping components within the sump; collecting and containing leakage from double walled piping that encounters the sump; containing spills that may occur during maintenance activities associated with components within the sump; keeping groundwater away from the components within the sump in areas of high water table; and isolating components from the corrosive effects of subsurface moisture and soil.

The two more common types of tank-top sumps are: piping systems that house the top part of the submersible pump, known as “turbine” or “STP sumps.”; and fill sumps that house the fill pipe and Stage I vapor recovery riser.

Other riser pipes, such as the probe risers and water gauging and removal ports, may also be housed in piping or fill sumps.

See also PEI/RP900 and Sump.