Man you guys are fancy... My water topoff system consists of me and a gallong jug.
coralnutz, that was the way i've ALWAYS done it also, and am still doing it that way but i need something more automated that i can rely on so i can go away for an extended weekend, or if i'm just way too busy to add water to the tank every day or two. right now the sump part is quite big, as i can withstand about 5g, maaaaybe 6g of evaporation in the sump before my pumps will start sucking air. i made it that big on purpose b/c i knew i would be lazy in adding new water, and hoped it could go about 3 full days without needing water.
however, i'd like to make a bigger fuge area, which means less return area. i.e. i would need to have something kinda of automatic auto-top off in order to achieve that same 3-5day window (or longer) without having to check on it.
twon, i lose about 1g of water per day right now. during the summer or when i have the fans blowing hard to keep the temp down, i sometimes lose 1.5-2g/day.
i looked through my manual, and the way i read it is that the top-off control module is just a transformer, that connects the water sensor to the LM3. you would still need to purchase an additional pump to add top-off water. as the module just turns one of the pumps (A, B, or C) on and off accordingly.
i guess that makes sense though, if i set the pump to 3.7L/day (1g), it would never over shoot that mark b/c its essentially "dosing", and not turning a pump on full force and relying on the float switch or sensor to cut it off. so i guess the fact that it is dosing a set amount per day anyways, it is essentially a back up system in itself. so i can never over shoot and over fill the sump as long as my evap rates stay somewhat constant.
so what is the point of the sensor then?