Where is my water going?

Reef_Frank · Dec 13, 2022

I have a situation that I really can't get my head around and was hoping someone had some suggestions. The water level in my tank seems to drop over time - to the point that a week after a water change the return chamber will be empty and the pump starts to blow air into the tank.
I have an ATO and it appears to be working correctly as the salinity is stable throughout all this.
I'm not sure what other steps to take to stop the return chamber (and sump in general) having such low levels. Water seems to be basically disappearing.

Thanks in advance for any suggestions!

LiamPM · Dec 13, 2022

Id say you need to check the ATO is doing its job fully - Where is the ATO sensor and where does the RODI water get pushed back into - Can you test it and remove a couple of cups of water from the display and watch the ATO kick in and add RODI back in? I take it after a full week youve had to top back up the ATO container with plenty of fresh RODI so know its being sent into the tank?

It almost certainly has to be an ATO issue realistically - I wouldnt rely on the salinity being stable as a way of saying the ATO is working as it should, salt creep entering back into the tank etc can sometimes cause this anyway.

Boreas_SA · Dec 13, 2022

Is your ATO float switch in the final return chamber of the sump?

Reef_Frank · Dec 13, 2022

LiamPM said:
Id say you need to check the ATO is doing its job fully - Where is the ATO sensor and where does the RODI water get pushed back into - Can you test it and remove a couple of cups of water from the display and watch the ATO kick in and add RODI back in? I take it after a full week youve had to top back up the ATO container with plenty of fresh RODI so know its being sent into the tank?

It almost certainly has to be an ATO issue realistically - I wouldnt rely on the salinity being stable as a way of saying the ATO is working as it should, salt creep entering back into the tank etc can sometimes cause this anyway.

Thanks for the reply - I'd ruled out the ATO being an issue because the salinity was stable but I'll definitely make sure it's working properly now. It's a red sea reefer tank with the ATO that comes with it - the ATO sensor float is in the return chamber and that's where the RODI water gets sent to.
The ATO empties every 4 or 5 days on average I'd say, (hard to know exactly how much is lost every day as I keep it topped up daily), but I'll definitely make sure it's working as intended.

Reef_Frank · Dec 13, 2022

Boreas_SA said:
Is your ATO float switch in the final return chamber of the sump?

Yes it is - but I will have to make sure it's working properly as your comment and the comment above have made it clear the ATO is likely an issue

A Young Reefer · Dec 13, 2022

make sure your return gate valve is properly tuned, the micro bubble sponge that come before your return chamber is not clogged and that your ato is working properly.

exnisstech · Dec 13, 2022

If the ato is working correctly the ato would empty into the return chamber because that is where the float valve is. No matter what the cause if the return chamber is running low the ato is not working or the ato container would be empty as it is a float switch so it will drain untill the return is full or the ato is empty. Not sure how old the tank is but I recently had to clean the float switches on my rodi and fresh salt mix brute containers as they were plugged and barely dripping. Easy enough to test, pull the float down and see if water flows through.