Grocco AS100 Bilge Pump Switch 
 
Switch turns bilge pump off and on  by sensing changes in pressure (caused by rising or falling bilge water level) in its air tube. No floats to stick or fill with water.
Approximate levels are "ON" at 2-3/4" of bilge level and "OFF" at 1".
Use with a pump that draws up to 10-amps running continuously or up to 20-amps running intermittently.
 
Manual