What is a tank or pit that receives sewage or waste located below normal gravity system grade known as?

A tank or pit that receives sewage or waste located below the normal gravity system grade is known as a sump. A sump is designed to manage wastewater that cannot flow out by gravity alone, often collecting water and sewage for pumping to a higher elevation where it can be treated or drained away. This is particularly important in places where the level of sewage must be lifted to reach a sewage treatment system or another disposal method.

In contrast, while a sewage basin receives waste, it typically does so at or about the level of the gravity system, not below it. An effluent tank is commonly associated with the storage of treated wastewater rather than raw sewage. A septic tank functions to treat and store sewage on-site, but it is traditionally not used for the purpose of pumping sewage from a lower elevation to a higher one, as a sump would. Therefore, recognizing the specific functions and arrangements of these systems clarifies why a sump is the appropriate term for this scenario.