How Does an Aquarium Float Switch Work?

An aquarium float switch is a device that automatically refills an aquarium's water when it goes below the desired water level. Since some species of aquarium fish can easily feel stressed with sudden changes in the water's level and condition, hobbyists use float switches to ensure that an aquarium's water level is always at its optimum condition.

  1. Parts of the Float Switch

    • A typical float switch consists of three parts: the outer shell, the body and the switch assembly. The shell is waterproof, as even a small leak will damage its electrical circuitry. The body and switch assembly contain a snap-action switch with a lever arm, a switch float mount screwed in place, a magnet and a conduit connection.

    Operation

    • When water level in the tank drops due to evaporation or a leak, the float will fall together with the water level. This causes the float switch to activate and send a relay signal to the top-off pump to start refilling the tank. The other end of the pump is connected to a water supply tank. Once the desired level is reached, the float switch goes back to its previous level and automatically deactivates.

    Float Switch Types

    • There are two types of float switches: the Auto Top-Off (ATO) pump float switch and the level kill switch. With an ATO float switch, no magnets or reed switches are required and the pump apparatus is directly controlled by water level. Tank inhabitants and deposits do not affect the float switch operation. The level kill switch type relies on specified water levels from the water source before the main tank is switched off. This mechanism's principle ensures that water does not overflow and also averts prolonged float switch pump operation.

    Float Switch Configurations

    • Float switches can be configured in three ways. The first one, a single-point water level system, relies on magnetic principles and uses a primary switch to turn the pump on when the float falls. This works without a safety float switch and is only required for water level maintenance. The second set-up is a multilevel configured type, where the user can specify a desired amount of water that goes into the tank, averting unexpected overflows. In the third configuration, the secondary switch is mounted at the lowest point of the supply tank. This configuration monitors constant water level and ensures that the relay automatically shuts off when the supply tank runs dry.