A true grinder pump will actually chop and shred the sewage and pump it through a 1-1/4″ pipe. These are powerful pumps, usually 1 or 2 horse power and 230 volt depending upon the brand, they in fact are capable of pumping the waste for over a mile to a gravity sewer.
A sewage pump for most residential applications is either a 4/10 or ½ horse power and 115 volt, they have a 2″ or 3″ discharge and they will , in most cases, only need to pump up to 15 feet of lift to a gravity sewer.
There is a huge difference in the replacement cost of the grinder pumps, which can have a $2,000.00 to $3,000.00 retail price depending upon installation and labor. The replacement cost of a sewage pump could be in the $400.00 to $600.00 price range depending upon installation and labor.
The typical sewage pump installation we see is where there is a bathroom group of fixtures in a lower level that drains and collects into a basin and gets pumped to a gravity line which is connected to the gravity sewer or septic system. The sewage pump is usually installed in that 18″ x 30″ or larger basin with a sealed cover, sealed vent and discharge, and a check valve to prevent backflow from the gravity sewer.
A grinder pump is usually used in jobs where the gravity sewer is a long distance from the home, or there is a high vertical lift of 30′ or more, and in a lot if situations, is part of a pressure sewer system. There are in fact whole subdivisions where all the homes have grinder pumps. These have sewer laterals that are 1-1/4″ with sewer mains being 2″. The ground up waste is pumped to a municipal sewer station for treatment.