Hydro Air Bilge Pump Switch | Jabsco 59400-0012 Hydro Air Bilge Pump Switch A new, ultra reliable bilge switch, which will automatically operate bilge pumps once water level reaches 2 1/4 in. (57 mm.) As water rises in the bilge, air pressure in the bell and tube increases, operating a diaphragm switch in the switch unit All electrical components are clear of the water and no sensitive electronics are used Proven highly reliable design using new moulding techniques Styling compliments modern interiors Automatic operation of bilge pumps of audible and visual high water level alarms Turns on at 2 3/16 in. (57 mm.), off at 1 in. (25 mm.) Diaphragm switch can be mounted up to 10 ft. (3 m.) above plastic airbell Switch - 6 in. long x 1 3/4 in. high x 3 in. wide (15.2 cm. x 4.5 cm. x 7.5 cm.) Airbell - 2 3/8 in. long x 1 1/4 in. wide x 4 in. high (6 cm. x 3 cm. x 10 cm.) For 12 Volt dc, up to 20 amps