How the Automatic Sensing pumps work -
The “S” series Automatic sensing RULE bilge pumps work on the principle of impeller resistance. They DON'T need a float switch - they are fully Automatic sensing pumps. The pump turns on every 2 1/2 minutes for about 1 second
to sense for water. If water is present, the pump will sense resistance at the impeller and continue to run until the water is removed. After that, it will resume checking for water every 2 1/2 minutes. The water level is kept between 1/8” 3mm low and 3/8’ 10mm high.

Next-generation compact submersible 800 GPH Automatic Sensing electric bilge pump - no float
switch required. Totally submersible pump with water-cooled, ignition and TCO protected motor,
stainless steel shaft and snap-on strainer base.
This pump is extremely efficient, draws low current and offers high capacity output in a very compact
housing, to fit into the smallest available space.
Please note - using the included check valve will reduce the output flow of the pump.
Consumes only 0.20 amps per day. 12v DC only - Cannot be run through 240v to 12v transformers.
Available in 12-volt model only. 3-year limited warranty.

• Fully submersible pump - 800 US gallons per hour - 
• Higher flow-optimized impeller to provide greater flow at the same amperage as the previous model
• High efficiency, low amp draw ignition protected motor includes true Electromagnetic suppression (EMC)
• 16 gauge tin coated copper electrical wiring with silicone infused water blocking feature-to stop water wicking down inside the wiring
• Built-In thermal cut-out (TCO) in the motor provides additional protection for pump & vessel
• 
  Backflow prevention - now includes a removable check valve in the discharge nozzle which reduces the amount of water draining back from the pump discharge hose into the bilge. Please note - using the check valve will reduce the rated output flow.
• Threaded discharge port - gives easier installation and maintenance.
  Discharge hose port is included with each pump
• Hidden air vents in the pump prevent air locking in challenging plumbing installations and helps with the check valve operate