Need some advice on an ATO system

[Steve'o]

Pretty new to reefing - 7 months now and constantly learning.
I have gone from a 29Gal up to a 90 Gal that I have to keep adding water to almost every other day.
I would like to have an Automatic Top off system for the tank but it is way to far from any water source.
I was thinking of having a large barrel close by the tank that I could keep full and would top off my sump when it get's below a certain level...
Any ideas on what I would need and how to do something like this without flooding my finished basement?
Thanks,
Steve'o