Sump levels, ATO and evaporation

[bkostuch]

I have a 3 chamber sump/refug. First chamber is the skimmer chamber and the water is about 3/4 the way to the top, which I think is normal. Second chamber is the refug and the water level is about 1/2 way and trickles over the baffle through the filter into the third chamber. Third chamber is the return chamber, the water level fluctuates a good bit here. I attribute this to evaporation as I am filling about a gallon a day.

So on to my question, with an ATO I am assuming I am placing the float in the third chamber where the water is fluctuating the most correct?

 

[butch]

I have a similar sump and that is where I keep my float valve. The water level remains very constant.

 

[tbub1221]

Correct