When walking around basements with clients, especially with clients who are first-time homeowners, they will often ask, “why do we have two sump pumps?”. While some basements do have multiple sump pits, usually what the client is noticing is the lift pump. So what’s the difference?
The sump system takes water from around the foundation of the home and replaces it somewhere less problematic. Basements with a sump system have drainage tiles around the perimeter that allow water to flow into them and then into the sump pit. Inside the pit there is a pump equipped with a float (similar to what you would see in a toilet tank). When the water level in the pit rises high enough (raising the float with it) the pump is activated. The water is then pumped out and into a discharge pipe that directs the water (ideally) 10 feet away from the home where it won’t be a nuisance. It’s a good idea to back up a sump system. You can read more about that in this previous post.
The lift pump has a completely different function than the sump system. While the sump system deals with outside water and keeping it outside, the lift pump system is responsible for handling wastewater from inside the house (basement level) and getting it into the drainage system. These systems are for homes with overhead/drain to street sewer lines (see photo). The mechanism is similar in that as wastewater (from bathrooms, AC line set runoffs, etc) fills the pit the rising level lifts the float and activates the pump which discharges the wastewater into the drainage system. If there is a bathroom in the basement the pit should be equipped with a masticating pump to handle solids discharged into the pit.
Pro Tip: Check on your pumps once in a while as mechanical components don’t last forever and can fail. When in doubt, reach out to a contractor for help.