This is NO type switch which closes on sensing of raising water level. It can be changed to NC by changing the cylinder direction.

Easy to install float switch sensor for water tank overflow alarm system. There is a snap type connector that plugs in directly on any 3/4 inch dia pipe. This size pipe is commonly found to put water into the overhead tank. Comes with 1 meter of wire. 

Use them with hydroponics, saltwater tank, freshwater tank, gardening, aquariums for power head control, pet bowls, fish tanks, filtration, heating, pumps, ponds, basement alarms, boats, air condition drain pans, pressure washers, carpet cleaning mach, reef aquarium, fluid control, ice machines, coffee pots, marine, automotive, automobiles, tropical fish tanks, evaporator coils, condensation line, in relays, or what ever your project may be. It can be easily converted from normally open to normally close by inverting the float.

Note: because the current that the switch can carry is much little (0.5A), you must use a relay or contactor when it is connected by a load, relay and contactor are not included here.