Where to add Top off water?

[eliramos]

It's not safe to add water in any location separated from where your topoff level sensor is.

The sump return chamber is a great place for the ATO level sensor, since it's the primary site of evaporation loss. Ideally, you should add the topoff water back there. Adding water elsewhere in the sump isn't bad if there's nothing preventing free flowing water to the return chamber - but there may be delays between water being added and the return level. If you add water to the display, it will eventually oerflow into the sump, and raise the level in the return chamber but with both a potential larger delay or blockages.

The only gotcha when running an ATO topoff line to the sump is ensuring that the source reservoir is lower than return site to prevent siphoning. If your ATO reservoir is higher than the ATO topoff line, you can create a raised siphon break to address this.

Happened to me once... That was a fun day lol

 

[twreefer]

It's not safe to add water in any location separated from where your topoff level sensor is.

The sump return chamber is a great place for the ATO level sensor, since it's the primary site of evaporation loss. Ideally, you should add the topoff water back there. Adding water elsewhere in the sump isn't bad if there's nothing preventing free flowing water to the return chamber - but there may be delays between water being added and the return level. If you add water to the display, it will eventually oerflow into the sump, and raise the level in the return chamber but with both a potential larger delay or blockages.

The only gotcha when running an ATO topoff line to the sump is ensuring that the source reservoir is lower than return site to prevent siphoning. If your ATO reservoir is higher than the ATO topoff line, you can create a raised siphon break to address this.

^^^ THIS ^^^

Put your topoff sensor and ATO water fill in the return section. File this under "learned the hard way". I used to return water to refugium, but unbeknownst to me, my foam block filter separating refugium and return was very slowly becoming blocked. One day, it reached a point where water flow was slowed down to a point where my ATO kept filling faster than the replaced water could make it into DT, overflow, sump, past the blocked filter, and finally into the return area. This caused the ATO to overfill my sump, resulting in several cascading problems....

1. Extra ATO water with kalk flooding my tank resulted in a calcium spike of nearly 70ppm = coral shock
2. Increase in water height in sump caused skimmer to overflow, filling sump with yucky skimmate
3. Above also leading to overly cloudy DT
   
4. Stink, mess, cleanup

While having a clogged foam block filter will always cause this issue, having ATO water go in upstream of it will accelerate the crash. If you are diligent to ensure you don't get blockages (as I am after experiencing this nightmare), then you will be safer going somewhere else in your system. However, even though I am now hyper-aware of the foam block filter slowdown, I still put my ATO water into the sump return area for extra safety.

Also, since we are on the subject, I recommend a water leak sensor outside your sump. My problem had only been going a short while, when the skimmer overflow caused water to go outside the sump where I have a water leak sensor placed which quickly alerted me to the problem. Of course, my ATO reservoir is only 5g, so that does limit how bad it can get, but you still want to get in front of such issues as quickly as possible. I use the Leaksmart sensor which will send an alert notification to your Apple or Android phones so you'll know wherever you may be, in addition to an audible alarm. Bonus, it also reports air temp.

Another recommendation, I use a shower pan liner (the kind from HD or Lowe's that is meant to go under tile in custom shower builds) under my sump. It goes up the walls in my stand, giving me the ability to withstand up to 5 inches of water standing around my sump as extra precaution before running all over my floor. Fortunately, it has only had to protect me from a few millimeters of water, which has happened on several occasions. This also allows any problems to cause the water to stand (rather than run away across your floor) so that the leak sensor can definitely catch the problem.

 

[srad750c]

I had mine hooked up to my return section but when I filled my ATO container up a siphon started when the pump turned off. Had to move to my DT after speaking with Tunze customer service. Anyone know if an inline check valve will keep it from siphoning?

Make sure its not in the waterflow, you won't have a siphon issue. My ATO feed tube is well above water line to prevent back siphon. My ATO water is only R/O water, no additives.

 

[Volcmreefer]

It is, thanks srad!