joesreef... that's understandable about the water level issue with the timer. With mine setup the way it is now, my level varies about 1/4" which is the evaporation of 1hr45mins, but the variation of water level will depend on how big or small the return section of the sump is. My entire sump is unbaffled, so the whole thing evaps evenly, so the level drops slowly with evaporation.
Waggs, here's a couple quick pics of mine (sorry it took so long). This is just to give an idea, and probably should be cleaned up a little bit.
Here, you can see the float bracket in the sump and the wires coming from them. The two black wires on the left from the sump go to the little black box that has the relay (seen in next pic). The bottom float sits down in the white cup. The white cup has only a few small holes drilled in it, so when the sump level bounces up and down from the high flow, the level in the cup stays mostly constant, so the switch isn't kicking on and off constantly.
Inside-the-sump shot of the floats. You can see my top (emergency) float is too high. It should be closer to the bottom float so it will shutoff the topoff pump sooner in the case of a sticky bottom float.
You can see where I have the relay box mounted here. Not the best spot, but I haven't moved it since I rearranged the sump. Put it somewhere out of the way.
The timer with the 12v relay power adapter. Notice that since my bottom float got sticky couple day ago, I haven't had time to clean it, so I just changed my schedule to topoff every 4hrs, instead of 2hrs. Set this to whatever works for you to keep sump level from varying too much (if your skimmer is in there)
This is my ATO reservoir, RO/DI, topoff pump, and tubing everywhere! Labels should help..
Inside the ATO reservoir. I use kalkwasser, so the feed line for ATO pump doesn't draw directly from the bottom, but 1" above it. I also have the float setup so the inside water level doesn't go up to the actual inlet of the float valve, so there's less chance of kalk building up on the float valve and sticking it open.
And last, you can see where the ATO line comes into the sump. It is zip-tied to the return line. It has to be high like this (above the highest water level of the ATO reservoir) to prevent a siphon continuing flow after the ATO pump turns off.
So, nothing special here. This is just the way I do it with pretty good results. Maybe others can give ideas how to make this better or cleaner. Hope that helps...