Are any ATOs really safe?

[Hawkaholic]

Limit your resivour to the amount that can be safely added without overflowing is one fail safe to add.

Use air breaks - Don’t put the end under water in the tank to eliminate back flow problems.

And a snail will find its way into an overflow and flood the place anyway. Lol Murphy. Add flood/water sensors of your choice to help limit the scope when the inevitable accident does happen.

 

[Lbrdsoxfan]

Double float switch (Hi/Lo), max runtime coding via apex, siphon break and a inline check valve. Cant do much more than that, imo.

 

[workhz]

Big sump, small reservoir, no problem.

Yep. 29G sump here with 5G res on a 90G tank. I do have a 2nd 5G res on a pump that I can electronically turn on to supplement the ATO.
Can’t imagine a 0-5G (averaging 2-3G) ATO dump is going to do much except send the skimmer into overdrive.

 

[Reefin' rumors]

Avast marine ato...

 

[gbroadbridge]

I think ATOs are a pretty interesting topic, mainly because of the potential risk of flooding your floors from a faulty ATO overfilling your tank.

ATO devices just seem to always bear that risk. Firstly, you will have multiple points of failure. I know many praise the Tunze ATOs, but even here you will still hear a few stories of overfilling the tank.
Many ATOs include a chip-based failsafe, where if the device is turns on the pump for more than a given time frame, it will automatically stop the pump. Or, alternatively, it can detect if a sensor seems faulty. But if any of you work in tech, you also know how often chips can fail (especially the cheap ones used for aquarium equipment). So, single point of failure right there.

I do hear of mechanical ATOs, often gravity fed, which does make a lot of sense, but isnt always an option for those with small AIO tanks, where you dont have enough space for a high quality float valve, as they are quite bulky.

So, are ATOs ever REALLY safe, or is it just a major risk we will always have to take as saltwater hobbyists?
Are there any redundancies or failsafes you can implement to reduce or eliminate the risk entirely?

The ATO refil that I use has two optical sensors and a final safety which is a mechanical float valve.
If all else fails that physically prevents any more flow.

I travel a lot, and that lets me sleep at night when I'm away for two months.

AUTOAQUA

www.autoaqua.com.tw

 

[Jason Scalise]

I had some similar thoughts for my 20g AIO.
I prefer the gravity fed approach with float valve and several redundancies.

I built this to accommodate those goals.

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[Crotalus]

There is very simple way of insuring that your ATO can never over fill the tank. My sump is 39 gallons. My ATO is a 10 gallon aquarium. Even if the float valve sticks, and it has, and completely empties, the sump doesn't fill over the top. The sump has more than 10 gallons of room above the sumps normal level. The water is about 1 inch below the top when the ATO is empty. I refill the 10 gallon ATO about every 4 days.

 

[JC1977]

My Tunze started acting up on me even after cleaning the optic sensor. I finally got tired of it. Pulled the Tunze and the ro/di container and now I pour a gallon of water into the sump every morning while my coffees brewing. Done. Nothing to malfunction or cause a flood. Not too high tech but it works lol.

 

[bakbay]

I had an old Tunze ATO (first gen with just the float valve) ceased up on me (likely due to Kalk) and flooded the house (garage). The 5g reservoir with a float valve was connected to the RODI but I forgot to turn it off. I’ve since bought a new Tunze with optical + float valve. Lessons learned for me: always turn off the valve to the reservoir!!!

It was my secondary tank — so not a big deal. The whole tank turned white, including all SPS frags! Softies miraculously survived though…before & after pics attached.

 

[cryptodendrum]

I built my own ATO as part of my complete Home Assistant based Aquarium Controller in 2017. This May comes on 6 years it's been in production for my multi-tank system and my ATO function has NEVER overfilled my sump or caused water to touch the floor. I've literally had the Open Source design fundamentals posted on the Home Assistant forum all this time too.

The design magic is not that difficult and I am stunned that it is not common to find this kind of super simple feature set. You can even combine it with 2 or three water level sensors, if you like for additional fail safes.

Use a peristaltic or very, very small slow flow pump from the fresh RO water reservoir to the sump. Figure out how long it would take using that very, very slow flow pump to over-fill your sump to maximum safe levels with a stopwatch timer. For very small sumps, this might be 10-20 minutes - depending on the flow rate of your pump. For very large sumps, it could be hours.

You will probably not want to just consider the water level in your sump, but also potentially - depending on your system - the risk of salinity reduction. But this will depend on the size of your sump relative to the size of your total system. In my case, I have a 2000 liter system with a 90 liter sump, and I usually run that sump at only 30%-40% fill level when everything is running; when ever stops (say a power cut) the back fill will bring the water level up to about 70% full. So I never want the RO ATO to fill more than 25% over the normal run time water level. And that extra 25% over the run time normal water level will not impact my salinity of my 2000+ litre system in any negative way.

Since I use peristaltic pump for my ATO, to fill my sump that extra 25% above normal levels, it takes about 2 hours. That 2 hours is my max safe runtime of my ATO. Once I know the max safe runtime of my ATO - I programmed that max runtime as a timer in the function of my ATO. If it exceeds this 2 hours runtime, it shuts down the ATO pump with prejudice & raises an alarm demanding I respond and investigate.


In addition to that; I also rely not on just ONE relay to activate and deactivate my Peristaltic ATO Pump - there is a second Safety Cut Off relay. The primary daily use relay is in the Peristaltic pump unit itself; and that's the one that takes the most beating. But that Peristaltic pump unit is also plugged into another smart power bar which is also controlled by my controller. If my peristaltic pump unit glitches out, stops responding, or reports that it's turned off but another secondary water level sensor gets triggered (indicating the primary relay failed) the ATO function in my controller will drop the power to the complete peristaltic pump unit itself.

 

[Mperry622]

I run the Apex ATO. I have the liquid level sensor and high and low sensor. I run my ato direct off my RODI line. Almost a year and the only floods i have had are when i manually turn on RO and walk away from tank :-(
I have the little RO line cutoffs from brs. If my sump level raises more than 4" it triggers the hard cutoff on the line.. But I will tell ya the little apex solenoid that is off until power is applied heaven sent. it just works. (i know until it doesn't) My kids know if the fridge water doesn't work. Go get daddy he has a problem

 

[Schmidt Aquatics]

Lots of interesting replies here!

 

[Schmidt Aquatics]

 

[salty joe]

My kids know if the fridge water doesn't work. Go get daddy he has a problem

 

[Schmidt Aquatics]

There is very simple way of insuring that your ATO can never over fill the tank. My sump is 39 gallons. My ATO is a 10 gallon aquarium. Even if the float valve sticks, and it has, and completely empties, the sump doesn't fill over the top. The sump has more than 10 gallons of room above the sumps normal level. The water is about 1 inch below the top when the ATO is empty. I refill the 10 gallon ATO about every 4 days.

Yes, that definitely works. However, for those of us who dont have a sump, running an AIO system or similar, that is sadly not an option… Water level will always be high, and can maybe only hold 1-2 gallons of water before flooding over the sides

 

[salty joe]

So my final fail safe is mechanical. If the tank overflows, the overflow gets caught in a galvanized steel pan placed under the stand (also nice for providing level surface on office carpet):

The dimensions of that pan can hold 4 gallons of water. Remove the space taken by the stand frame (hollow between), and I would guess it can comfortably hold 3 gallons before spilling onto the carpet.

With a 5 gallon ATO jug in the stand, I think it can overflow the tank, but probably not by >2-3 gallons. So, worst case in terms of office mess would be having to drain the pan (siphon or towels). Worse for the tank inhabitants, of course. Corals/fish might not like the diluted saltwater, but still might not be too bad. Urchin would die for sure, as well as anything else sensitive to salinity swings.

I did the same sort of thing but ran the overflow into a sink and added an alarm.

 

[Dburr1014]

My tunze has been flawless for 6 years. Even the original pump still works.
If it's on to long, it shuts off. If it can't read low, I will catch it before to long.
If for some reason it does over-fill, my leak detectors will shut off the ato, auto-refill of the ato can, and the main pump.

 

[Paul B]

I don't trust many commercially built products (especially if they are made in China) so I build everything myself.
My ATO is gravity fed. I have a 5 gallon bucket above the tank hanging from the ceiling
(This is in my Man cave so it is not obtrusive, but cool looking)

The bucket gets filled from the RO/DI and shuts off by a float connected to an old mercury switch from a vintage thermostat. (mercury switches can't really fail) The float shuts off the electric valve which sends water through the RO/DI.

The water flows by gravity to my float valve on my tank (I don't have a sump)

The water is fed to the tank through a small 1/4" tube with a valve, and the water only flows a little more than the tank needs for evaporation which is about a drop a second.

I have been using this exact set up for over 45 years with no flood yet.
Of course the day is young and anything can happen.

 

[Cool Fish]

I use a simple light timer as a time limiting backup. I also have a video camera on it to watch for a malfunction when I’m away.

 

[blackbeltmom]

This is the exact reason that I do not plumb my RODI into my ATO. I love my SmartAto and have never had one fail and keep filling. I have had them not run when the prism is dirty, but so far that's all. I have a 10-gallon Trigger ATO container. It could still flood if the ATO container is full, but it is rarely full to the top. I also have a tile floor, so why I don't want water on the floor clean up would be fairly easy. I have thought about looking into possibly having a backup that shuts down the ATO if the sump gets too full.