View Full Version : 5017 ATO problem

05/23/2017, 06:34 AM
Hi Tunze Experts,

My ATO is a few years old now and it started overfilling my tank. My reservoir is emptying twice as fast as normal and my Alk, Ca, and salinity have dropped. I cleaned the sensor with a toothbrush and tried repositioning the sensor. But I'm still topping off at an increased rate raising the level in my sump which makes my skimmer cup fill up much faster than normal.

Any thoughts on what could be causing the issue?


05/23/2017, 09:24 AM
Since the sensor is designed to fail in the off position and a failure in the on position is very rare, my suspicion is something was moved or added so either it is bubbles on the sensor triggering a fill or if the reservoir was changed or the hose rerouted a siphon is present and water is siphoning in. If it fills past the float, it can only be a siphon, if this tends to coincide with a recently refilled reservoir it is also most likely a siphon.

05/23/2017, 09:17 PM
Hi Roger, I added a GFO reactor a few weeks ago and had the output dumping to the bottom of the 3rd sump chamber where the ATO sensor is mounted. I'm not sure how it would impact the sensor but the timing roughly aligns to when my issue started. I moved the GFO to the 1st and 2nd chambers to see if that fixes it.

05/24/2017, 08:48 AM
Likely this was a source of bubbles, the optic sensor only detects air vs water and will interpret bubbles as being dry.

05/25/2017, 09:04 PM
So far so good. Thanks Roger. Never would have thought of that.