Bulk Reef Supply

Float Switch - Vertical Mount

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The Standard Generic Float Switch is great for:

  • General water level control applications
  • Aquarium top-off applications
  • Humidification/de-humidification applications
  • Hydroponics projects
  • Water features
  • Air conditioning drain pan applications


The wires complete a circuit when the float is down. You can reverse the operation by removing the clip, turning the float upside down and replacing the clip.


Recommended for water applications like level controllers, auto top systems or other aquarium uses.

  • Normally closed or normally open (see more)
  • Float magnet is encased inside the float
  • 48" leads (22 gauge wire) offer project flexibility


M8 fitting – includes a nut and sealing O-ring


Note: Don’t use in heavy duty applications like sewage pumps.


A pump rated at just 5 watts can destroy a float switch rated for 50 watts, locking it in the “on” position and pumping a lot of water where you do not want it.


The magnetic reeds enclosed in liquid level sensors are extremely reliable and long-lasting when utilized properly. Failures are nearly always a result of current overloading. Pumps, solenoids and many other devices that require control by a liquid level sensor carry "steady state" current ratings. These devices can draw ten times (or more) their steady state power ratings on start-up or shut-down. When the reeds inside our switches are exposed to this kind of "spiking voltage" they can overheat and become deformed. In some cases they may even weld together or break off, causing the switch circuit to remain closed (or open) regardless of the level of the float. Deformed reeds can also function intermittently, causing problems with troubleshooting. A 50 watt float switch can be destroyed by a pump rated at 6 watts and, unfortunately, it may take many cycles before the failure occurs.


Because they can destroy an otherwise very reliable float switch, care must be taken to completely isolate the switch from the current drawn by pumps, solenoids or other devices subject to spiking voltage. Resistors or diodes may be used, but the most common solution is to utilize a circuit board or a relay.


In the illustration, a relay acts as a switch for a pump, thereby isolating the float switch from any spikes that the pump may draw. The float switch turns the relay coil on and off. In this way, the only current handled by the float switch is that small amount required by the relay coil. Please consult with your relay supplier to assure that the relay current requirements are well within the specs of the float switch.

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Product Questions

What size of a drill bit should I use for drilling the hole on the container (lid, etc) that I am mounting the float switch onto?
Question by: William on Feb 18, 2022, 3:27 PM
Hey William, the threaded portion is a M8-1.25 which will be roughly 8mm. I would drill a hole 6-8mm for installation!
Answer by: James Johnson (BRS Staff) on Mar 2, 2022, 12:22 PM
Would this work with a tunzee nano?
Question by: Yujiro on Jan 10, 2017, 3:37 PM
Great question! Unfortunately, this will not replace the Tunze Nano Osomolator float switch. You may need to reach out to Tunze directly for replacement parts. :-)

Tunze – 512-833-7546 tunze@sbcglobal.net
Answer by: Randy on Jan 10, 2017, 5:42 PM
What size is the Threaded Portion of the Switch?
Question by: Rory on Jan 19, 2016, 1:33 PM
Great question!
The threaded portion is M8-1.25. It is metric, but your local hardware store should have a plastic nut that works.
Answer by: Connor on Jan 27, 2016, 2:47 PM
Can this switch be fully submerged? I would like to use it near the bottom of a trash can I use for my ATO so I can be notified once it needs to be refilled.
Question by: Jennifer Munoz on Jun 26, 2015, 7:20 PM
Great Question,
This switch could be used in reverse to notify when levels are low. Switches can have a tendency to become stuck if left floating too long, so inspections must occur to ensure that the switch goes back down.
Answer by: Connor on Jun 29, 2015, 6:52 PM
Will this switch work with the apex breakout box?
Question by: CM on May 4, 2014, 6:36 AM
It sure would!
Answer by: Bulk Reef Supply on May 4, 2014, 6:36 AM
How does this switch mount to an aquarium tank?
Question by: Steve on Apr 5, 2014, 2:43 AM
Hi Steve,
This is just the switch itself, generally as a replacement part or a DIY component. It has a threaded shaft and a nut to secure the float switch, generally to an L shaped bracket of some sort but it really depends on what your going to use the float switch for.
Answer by: Bulk Reef Supply on Apr 5, 2014, 2:43 AM