Commercial stormwater pumps are necessary to remove storm water from areas that cannot be drained by gravity. Submersible pumps provide special advantages in simplifying the design, construction, and maintenance and, therefore, the cost of the pumping station. Submersible pumps are close-coupled pumps driven by a submersible motor and are a vertical type of pump. The preferred submersible pumps are those with non-clog impellers that deliver higher efficiencies with lower life cycle costs than the recessed impellers. Use of anything other than a constant speed, single-stage, and single suction pump is rare. The critical parameter is the time between stopping and restarting an individual pump, not how long the pump runs after it starts.