Thank you hlem for the additional info, would appreciate the actual measurement if you have time (the manual didn't provide actual dimension), it's going to be pretty close...
For the Smart ATO glitching, in one of the reviews I came across the reviewer mentioned that if there is a power interruption and the water level got higher than the unit, if the unit restarted under water it would continue to beep until the the unit is unplugged and restarted with the proper water level... could this be the case? (http://reefbuilders.com/2013/12/10/smart-ato-review-perfect-couple-quirks/)