I think we calculated it to be about 22 gallons, at 16"X16"x20". With two inches to spare at the top it will hold about 19 gallons.
I am about to oder this float switch from Amazon.
http://www.amazon.com/gp/product/B00FHBY7SS/ref=ox_sc_act_title_3?ie=UTF8&psc=1&smid=A1THAZDOWP300U
That will have one switch to warn me that the water is getting low in the reservoir and the other switch will prevent the pump from running. I was going to go with a gravity feed, but while testing my programming on the APEX I was blowing through the solenoid and it required too much effort. I figured gravity wasn't going to flow with that.
This is the pump I am ordering from Amazon because a lot of people said it worked for their ATO:
http://www.amazon.com/gp/product/B001BOD9JI/ref=ox_sc_act_title_5?ie=UTF8&psc=1&smid=ATVPDKIKX0DER
The low GPH should make for a nice gradual flow in to my sump. I think I am going to put the other double float in the sump. One side will kick on the ATO progrma and the other will shut down the return pump (which shuts down the skimmer and heaters) in case the sump goes to low. Unfortunately if I do that I have to ditch my switch that will tell me the sump flooded. The breakout box has six inputs and I will be full.
I created virtual outlets for all of the controls.
Skimmer_Full is for when the float switch in skimmer collection cylinder is tripped.
Sump_Low for when the ATO needs to kick on
Sump_High to turn off the skimmer when the sump level is high to prevent it from pumping too much water in to the collection cylinder.
Sump_Flooded if the sump level is way high (this is going to get replaced with the new outlet)
Sump_Dry will be the new outlet created so if the sump is too low it shuts down the return pump and then the skimmer and heaters automatically go off with that.
Reserve_Low to let me know my reservoir needs water
Reserve_dry to shut prevent the ATO pump from running dry
I created the virtual outlets because it was easier to know why the APEX texted me with an alarm. Rather than trying to remember when switch 6 opened, what switch 6 was for, the alarm tells me what outlet just engaged, and therefore tells me that the skimmer is full.
The ATO pump will shut off when the Sump_Low switch closes, and is backed up with the Sump_High outlet as well. The Sump_Flooded outlet would have been a tertiary backup, but I am repurposing that outlet. I also have a manual float valve coming in to the sump that should shut the water off from the reservoir as well.
I know most of this wouldn't have bene necessary if I had just plumbed directly from the RODI unit in the basement, but I didn't garner permission to drill holes to run new water lines.
I also relocated my APEX probes to my sump and repurposed the APEX magnetic probe holder. That is what I am going to attach my float switches in my sump to. I figured this was safer than glueing the pieces we made today while my sump has aquarium water in it. This will also allow me play with the positioning of the switches to get the water level just where I want it.
Overall this has been fun. I have increased my knowledge of programming an APEX unit, and although I am not an expert, I am able to get it to do what I want it to do. And I learned how to weld acrylic pieces together to make a tank.
Thanks again, Shawn, this project has taught me more about the APEX and tank fabrication than I ever imagined that I would learn.
View attachment 23707
This was while under construction.
View attachment 23708
The finished product.
