ATO & salinity problems

[sundancekid]

I have recently started using an auto-top off. This is the first time I've used one & when I checked my SG recently, it was at 1.022. I had been keeping it at 1.026. I raised the salinity over a few days back to 1.026 w/ the ATO off, but the same thing happened again when I turned the ATO back on. I've been using just RO water for the top off. Am I being a dunce & should have the top off water close to a SG of 1.026 or somewhere between? I thought that there would be minimal salt loss with evaporation & that using RO water would keep the salinity fairly stable.

Any thoughts/advice would be appreciated.

[Playa-1]

RO/DI water would be the best choice for the ATO.

How are you checking the SG?
What is the time frame of the SG drop?

Is it possible that you have a leak somewhere that is yet to be detected?, or maybe the ATO is filling the tank to a higher level then where your filling it to initially at the 1.026?

[dwd5813]

<a href=showthread.php?s=&postid=14275542#post14275542 target=_blank>Originally posted</a> by Playa-1
maybe the ATO is filling the tank to a higher level then where your filling it to initially at the 1.026?
this happened to me when i first set mine up. i measured the salinity, measured the water level on the mounting plate for my ato, set the valves, and proceeded to figure out that the ato was filling past where i thought it would. adjusting the valves on the ato and replacing some evaporated water with saltwater with the ato shut off eventually got it taken care of. sounds like you just need to do some adjusting.

[sundancekid]

I've been using RO unit because I bought an RO unit thinking it was RO/DI & I still have to get the DI part.

I'm checking the SG with a refractometer & a float arm hydrometer. As far as the time frame for the SG drop, maybe a week-10 days... The first time it happened, I had the tubing below the water line & I thought I created a vacuum and sucked a bunch of tank water into the RO water & then added the really dilute water back into the tank. So, I wasn't really checking the salinity since I thought I had an explanation.

I thought about maybe the ATO filling it past where I thought.... but 0.004 is quite a difference in salinity & the tank is only 29 gallons. I hadn't done a water change between the time I raised the salinity & the time I realized it was low again so I don't think that I underfilled the tank & the ATO diluted it. It's got to be less than a gallon between where I have the float switch sitting and the minimal water level before the pump blows air bubbles.

Does this still sound like it might be a problem with the float valve? And if so, how should I adjust it? Just for background info: I bought this used from another reefer who made it from a DIY kit. It has two valves on it & worked fine for him.

[sundancekid]

As far as a leak goes, I don't think so. I haven't seen any evidence of leaks, although it's about a 110 in my place & drier than a desert so maybe it's evaporating as fast as it's leaking...

[dwd5813]

disregard salinity for just a second and figure out if the water level is where you want it to be when the ato kicks OFF. no? adjust the valve so that when it kicks OFF the level is right where you want it to be. once you have that straight, mark that level with a tiny corner of tape or something and leave it turned off until you see enough evaporation to raise the salinity back to 1.026. once the salinity is right, take some premixed saltwater at 1.026 and fill to the mark, and turn your ato back on. that should do it.

[Playa-1]

Either way, fresh water is what you want for the ATO.

I think a gallon could make the difference of about 0.003 in a tank that size. Some ATO units have a much tighter fill threshold then others. Every Inch in that tank is a little over 1.5 gallons so if the tank drops and inch before the ATO kicks on then you could be getting some pretty big swings in some of your parameters.

There's a few things you need to check into.

Is the discharge hose from the ATO above the tank now and not in the water?

Use some tape and mark the levels on the tank. Where you fill it to, Where the ATO turns on and turns off at. Check the Salinity at all three levels and see how much of a swing your getting. I would fill it to the level that the ATO fills it to and then turns off. The idea is to find out how much water the ATO is topping off at one time and how much of a swing it's causing for your tank. There may be away to adjust the swing with the floats depending on how it is set up.

[THE ROOK]

If you find your ATO comes on when the lower float is activated but does not stop flowing until the upper float is turned off, then he set the two floats up to a "latching relay".

You could test the system with quickly with salt water.
-Put saltwater in a 5 gallon bucket & put your ATO pump in it.
- Put some masking tape vertically on your sump wall.
- Mark current level.
-Then start removing water slowly until the pump activates.
- Mark level.
- Wait till pump stops mark level if not at original mark.
- Watch for level to rise with pump off indicating your siphoning from your reservoir. (my theory)
-Report back & we can help you fix that.

This should give you a good indication of the issue without stressing your tank.