Me neither. Interesting.What's a Laundry Sink Pump for? I've never heard of this before.
My guess is a slop sink that the washer discharges into, the sump pump then does the work to discharge the water out of the home.
The sewer drain is halfway up the basement wall so the sump pump has to pump uphill . The pic I posted attaches to the sink drain and water fills the bucket .Me neither. Interesting.
Fairly common in older homes with a basement to help retrofit a bathroom or laundry room. House I used to own was built in 1946.
Seems like poor planning on part of the builder.
2x How septic or city sewer line goes out of the building is not under the builder's control. Also, today's washers with small drain pumps will not pump over 6' from the floor unlike the old belt driven high-capacity pumps of the old washers to high waste connections so pump boxes are becoming more common.Builder had nothing to do with it.
The purpose of these units are to retrofit drainage relatively economically after the fact where there is no infrastructure for it.