Tunze ATO too sensitive

Ober_Reef · Jan 23, 2022

I recently got my ATO up and running again after giving up on it due to multiple overfills. I believed I solved the issue by eliminating slack in the output tubing that I thought was causing a syphon. I also purchased an ATO Reservoir that sits next to my tank and it has allowed me to pay more attention to how much is being pumped into my tank. After giving it a few days it pumped five gallons into my tank and I felt it was probably too much too fast. I checked my salinity with my Hanna tester and it was right around 33. To bring my salinity back up I have been adding salt water daily and checking my ATO Reservoir this morning I noticed water has been added to my tank. I’m starting to think either the sensor is faulty or too sensitive. It’s pretty frustrating as I have honestly never had luck with ATOs. It’s a Tunze 3155 I only used it for a couple months before giving up on it.

Just wanted to see if anyone has experience or helpful suggestions before I go back hauling water every couple days and the $150 reservoir becomes a dust collector.

Water Dog · Jan 23, 2022

Is the end of the ATO fill hose higher or lower than the highest water level in your ATO reservoir? If at any point, the end of the fill tube is lower than the water level in your ATO reservoir, then it will siphon water even after the ATO pump shuts off.

Jeffcb · Jan 23, 2022

Have you tried contacting Tunze USA in Austin TX. I had a problem with my 3155 initially. Mine just didn't work at all. I picked up the phone and called them I directly. The owner, Rodger answered and helped me solve my problem. He replaced the bad part / controller and it has worked great for the last year.

Ober_Reef · Jan 23, 2022

Water Dog said:
Is the end of the ATO fill hose higher or lower than the highest water level in your ATO reservoir? If at any point, the end of the fill tube is lower than the water level in your ATO reservoir, then it will siphon water even after the ATO pump shuts off.

Yeah like I said that’s initially what I thought was happening but I have checked multiple times when I hear the pump running and it shuts off pretty cleanly.

Ober_Reef · Jan 23, 2022

Jeffcb said:
Have you tried contacting Tunze USA in Austin TX. I had a problem with my 3155 initially. Mine just didn't work at all. I picked up the phone and called them I directly. The owner, Rodger answered and helped me solve my problem. I cant remember his name but he replaced the bad part / controller and it has worked great for the last year.

Yeah I think that will be my next step, I just wanted to make sure there was nothing I could do before I reached out.

Water Dog · Jan 23, 2022

PapaPat said:
Yeah like I said that’s initially what I thought was happening but I have checked multiple times when I hear the pump running and it shuts off pretty cleanly.

It doesn’t matter if the pump shuts off cleanly. Water will continue to flow if the end of the ATO fill hose is lower than the highest water level in your ATO reservoir. That’s what siphoning is.

ChiCity · Jan 23, 2022

drill a hole on the line at the very top
of the inside of the ato reservoir…
that’ll create a siphon break

Ober_Reef · Jan 23, 2022

Water Dog said:
It doesn’t matter if the pump shuts off cleanly. Water will continue to flow if the end of the ATO fill hose is lower than the highest water level in your ATO reservoir.

I meant to say that I stayed there to watch the water stop and it was not continuing to flow after the pump stops. Of course this was only a few times so I guess I can’t be 100% sure. I would say that the output is pretty close to even with the height of the reservoir if not a little lower than the top. I guess I could try suspending it a bit higher over the sump somehow.

Ober_Reef · Jan 23, 2022

ChiCity said:
drill a hole on the line at the very top
of the inside of the ato reservoir…
that’ll create a siphon break

The tubing is basically a slightly larger version of airline tubing so maybe poke a hole with a needle ?

Water Dog · Jan 23, 2022

PapaPat said:
I meant to say that I stayed there to watch the water stop and it was not continuing to flow after the pump stops. Of course this was only a few times so I guess I can’t be 100% sure. I would say that the output is pretty close to even with the height of the reservoir if not a little lower than the top. I guess I could try suspending it a bit higher over the sump somehow.

Suspend it higher than the highest water level in the reservoir and it won’t siphon anymore. Perhaps this video will help you visualize it…

My guess is that your ATO is only overfilling after you initially fill your ATO reservoir. Once the water level in the reservoir gets lower than the ATO outlet tube, the siphoning / overfilling is no longer an issue, hence your observation of the water stopping after the pump shuts off.