Backwater valves address reverse drain flow
A properly selected and permitted backwater valve can close when wastewater reverses toward the building. While closed, household drainage may also be restricted, so occupants need to understand operation and maintenance.
It does not pump groundwater or stop water crossing the surface toward a foundation.
Sump systems move collected water
A sump pump moves water that reaches the pit through the connected drainage arrangement. Performance depends on inflow, pump capacity, discharge, power, controls, and maintenance.
A sump pump does not clear a sanitary blockage or stop every overland path.
Name the water source before the device
Sanitary surcharge, groundwater, foundation drainage, roof or yard runoff, and river flooding are different hazards. A useful plan can combine measures, but no device guarantees flood prevention.