Some homes appear to have two “sump pumps” in the lower level: two pumps and two crocks in the floor, often discharging through a white PVC pipe. Why would a home have two pump pumps? Usually, it doesn’t. One of those pumps is a sewage ejector.
When the main sewer discharge pipe / lateral is installed above the floor of the lower level, sewage water must be pumped up to the lateral. This is very common with septic systems and can also be found with municipal sewer service.
How can you tell when one unit is a sump pump and the other is a sewage ejector? Trace the discharge of the pipe. A sewage ejector will discharge into the septic system or the municipal sewer line. A sump pump discharges to the surface or to an underground storm sewer. A modern sewage ejector has a sealed crock with a vent connection to the drainage, waste and vent system.
And just to complicate things, your home might have an older sewage ejector that’s not sealed, and it look just like a sump pump. Trace the discharge and connections to determine the type of system you have.