ATO diluting salinity
 

Something seem not right with your setup. I have 2 JBJ auto top off and never had a problem with any of them.

Why is the water level fluctuate in your sump???

Whenever I do water change or maintenance I turn my top off offline so that it does not continue to fill up fresh water.

Sounds like your overflow downpipe is not large enough to handle the volume your return pump is pushing.
How long has this been an issue?
Is it possible you have the ato control in the wrong section of your sump?

my durso overflow would do the same thing , i had 2 1 inch drains and a 500gph return and if i didnt tune the drains with air intake and choke valves they would pull full siphon and drain the overflow box then lose siphon and the return would pump the retun section way down . So you might just have to fiddle with it a bit.

Do you have a Gate Valve? The Herbie takes some fine adjusting to exactly match the full siphon flow rate to your return rate. Once dialed in it should be steady.

even with a gate valve it's just slight adjustments to get flow balanced. Once that's sorted out shouldn't have to worry about your ATO

Agreed something is not set right.


Should be irrelevant. Unless he is never stopping the ATO, the water would mix completely within a relatively short amount of time.

I would say maybe your salt level was wrong to begin with. Perhaps your refractometer needs calibration, or in the case of float style, maybe it's off by several points like mine was before I tossed it.

I meant if he does not have a gate valve and only a ball valve it will be very hard to make those slight adjustments. The Gate Valve makes life infinitely easier to find the sweet spot compared to the 1/4 turn ball valves.

Wayne, I haven't setup my new Tunze ATO yet, but I remember reading in the manual that there is more than one way to set the on/off pump level by spacing the sensors further apart.
Have you checked your's to see if you can have the leeway you need?

I have a gate valve on the drain pipe, not a ball valve. The herbie causes the level in the sump to fluctuate very very slowly but still enough to cause the ATO to turn on. Im assuming i just need to spend more time dialing it in and getting the flows to match up, thanks philg3.

I have a refractometer and it reads 1.025 after a waterchange and then a day later the salinity will be 1.024 or 1.023 so that rules out my refractometer needing calibration..

I don't think I can adjust much with this system. Its just a single float switch that turns a pump on when the float drops and turns it off when the float rises up. Maybe I will have to spend some more money and get a more elaborate system. The JBJ ATO is fairly cheap ($70).

Is your overflow plumbing able to handle full flow from your return pump ?
I ask as I noticed during testing mine that there is a correlation between my sump level and my overflow level. Not just the actual levels, but the water level in the overflow affects drainage speed and so on.
I am wondering;
If your overflow can handle full flow maybe it will help you stabilize the whole setup ?
Good luck

From what I've gathered, you're overflow isn't tuned precisely, and is causing a slow change in the sump level. Albeit a slow change, it is a change nonetheless.
There isn't an ATO on the market that will compensate for a mistuned overflow.

Is your overflow internal? My herbie is internal, and if it were to swing way out of tune and drain the over flow, I'd have an extra 4.5 gallons of water in my sump. That would cause an extreme difference in my salinity also.

I'd make sure your overflow is 100% consistent before you go ahead and drop some money on an ATO that isn't going to help your problem at all.

Have you ever calibrated? If not then its still possible its wrong.

However, depending on your salt, some needs to sit 24hrs to fully dissolve, like H2Ocean. If I use mine right away I can guarantee salinity swings.

Also, do you turn your ATO off before water change? Maybe its pumping extra top off in while you remove dirty water. Just a thought. Maybe you are not adding EXACT amounts of new water to removed water and then ATO is diluting to bring top up to correct water level?

Just think the solution is a simple fix.

Good luck.



Just makes no sense at all that the ATO is doing it.

Just needed a little more dialing in guys. Seems to be holding now.

Thanks for all the insight.