I've considered setting up 6 or 8 blue 55 gallon drums in series to my down spout. with a roof as large and steep as mine it would fill them in a couple of rains. It should let the debris settle into the first drum. After that most of the water would be free of debris. Filter or boil as I need it. I've also looked at putting one or 2 of those 1300 gallon farm tanks in one of my garage stalls to store the filtered water. Winter time would be the killer for that idea though.

Colt: No one needs to know about your well. If you can seal the casing air tight, you could put the well in your basement. You'd already have it down about 8' by putting it in the basement.

If you don't want to seal it, it could be put in thru the garage floor. Some areas will allow a well if it is for watering a yard or garden.