to my mixing station I come off the rodi to the water barrel. Water barrel has a float valve and a small JG type valve between the rodi and the float. When I want to fill the mixing barrel I open the JG valve a the float prevents a flood.

You go do similar, every few days refill the brute, your ATO doesn't short cycle your rodi.

Anyone ever use one of these? Although, now that I've thought about it for 2 seconds, I guess an Apex could accomplish the same thing...
http://www.buckeyehydro.com/hi-lo-ta...el-controller/

Apex with 2 float switches, or DIY with couple of float switches and a relay. Big thing is upper and lower limit you can set a distance (volume) apart.