"A sump pump is used to remove excess water from a home. There are multiple types, but they all monitor the water level to ensure that the water doesn't exceed a pre-set level and cause moisture intrusion or property damage. While most sump pumps are effective in removing water, they should always be covered with a gas-tight lid to avoid moisture problems, as well as to prevent the seepage of radon (and sewage gases) into the home. Home inspectors should encourage their clients to follow a scheduled maintenance routine and get an Annual Home Maintenance Inspection to ensure that their sump pump is operating efficiently and according to its estimated service life."
Deteriorated sump pump cover
Reference: Internachi - Inspecting Sump Pumps