View Full Version : ATO reversed flow

01-29-2018, 02:38 AM
Hi all,

Iíve recently had my Tunze nano ATO act up on me.

After i turned off the pumps to feed the fish, and then turning back the pumps on, the water somehow reversed its flow today, subsequently flooding my rodi water resevoir bucket.
I caught it quickly and turned off the ATO . Minimal damage done ...just a wipe with a couple towels.

Has anyone had this happen?

I have a RSM 250 and the ATO pours the water into the back sump.

The water tube was touching the water in the back chamber when i turned off the pumps.... is this the cause?

01-29-2018, 03:30 AM
Make sure you always have a big gap from the tube to the water surface. Otherwise, as soon as your pump kicks off it will back siphon out until the siphon is broken by the water level dropping below your auto top off tube...

01-29-2018, 06:51 PM
Thank you very much.

Iíll make sure to lift/elevate the tube and make sure it has no contact with water.

01-30-2018, 12:44 AM
a great way to do this while still having it silent, unable to splash all over the place and not get accidentally bumped out of place is have the ATO tube dump into a peice of PVC standing vertically with the bottom below the water line. the open top of the PVC will still allow air in to prevent siphon

01-30-2018, 03:41 AM
Itís a back siphon....

I had it happen one time, overnight it drained 1/2 a 65g tank... I quickly acted and saved it all, but lesson learnt......

Not again....