how the auto water changer works!

atu3-programmable 20 litre
atu3-programmable 20 litre
atu3-programmable 20 litre

atu3-programmable 20 litre

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Auto Top Up (not water changer)

ATU-Pro3 - 20 litre fitted with an infrared sensor

D:440mm W:180mm H:260mm (height does not include the cap - add 50mm)

This unit has been designed to be plug and play

includes pump/pipe/mounting etc 

shipping £12.50 uk mainland


Here are a few scenario's that have been reported on reef sites and what the ATU-PRO3 does if it happens.

  • The float physically jams because of a snail or similar
  • The float fails electrically
  • The float drops into the tank
  • The outlet comes adrift resulting in water outside the tank
  • The reservoir runs dry (possible pump burn out}
  • The pump gets jammed
  • and most important R.O. reservoir "dumps" its contents into the aquarium

In every situation above only the ATU-Pro3 will shut the pump down after a time period set by yourself with the options of 5, 10, 20 or 60 seconds. - exclusive to Reefloat - NO other brand has this facility

The ATU-PRO3/4 is pre-wired and the unit is ready to use - includes:

  • The programmable controller
  • Supplied with infrared sensor and bracket with 2m flex
  • A low voltage pump with a maximum height of 3 metres
  • A 2amp power supply
  • 2 metres pipe
  • full installation guide



In a nutshell it shuts down the pump so the top-up is inoperative until you come along and reset it, indication that it has shut down is via the pump LED starts flashing and the alarm sounds for 30 seconds, sounder then repeats for 2 seconds at 15 minute intervals. Reset is a simple push of the button, once to silence the alarm and twice to full reset - if the cause of the fault is still present then it will go back into alarm state


BONUS - Anti-Wave - many are familiar with the pump switching on and off every time you stick your hands in the water, or the same things happens if you have that powerful wave maker powerhead. This is addressed by a 3 second built in float delay activation, in other words the water level has to be "LOW" for 3 seconds before the pump starts, as soon as the level reaches a "HIGH" position the pump stops immediately. The distance between high and low level is not measurable by conventional means the sensor is that accurate!

BONUS - Memory - that preset time you set up stays unless you reprogam, it is not lost on power failure!


  • sensor - HQ infrared with magmount
  • sensor cable length 2 metres
  • water level variance - less than 0.5mm
  • voltage - 12v DC
  • alarm - visual and audible programmable 5-60 seconds, pump auto cut-off on alarm
  • pump - 12v DC with up to 3m head height
  • anti-wave - 3 second delay on pump activation

Customer Reviews

Based on 3 reviews
Can't ask for more

Perfectly faultless ato unit, will be looking into those water changers of yours!

Rob (Swadlincote, GB)
ATU pro3 20l

Excellent after sales, sorted out my hanger issue straight away. No fault of the ATU, just my setup and positioning.

R. (Swadlincote, GB)
ATU pro3

Excellent service and brilliant unit. Replaced my old ATU that used to kick in and pump about 3.5l water at a time, (FOWLR tank) old air sensor type.... this is under 0.5l at a time if that, plus has loads of safety features.
Had to amend the hanger/clip as it sticked out to far for my liking and leaked where you connect the hose to it (I'm sure silicone/clamp or simular would solve this). In my setup I know I would knock it off or snap it as that's the side of the sump I always go to and it's the electric side of the cabinet. I've just cable tied the hose to the outside of the hanger/clip and turned it round until I come up with a better solution.
As advised from Gordon went with the infrared sensor as my sump glass is 9mm.
Brilliant and would highly recommend