I have 3 rain barrels at 4 of my houses downspouts, I bought mine from Orschelins farm and home and they are recycled 50 gal barrels from Greece that had olives shipped in them, this is near the same way mine are done, mine are down for the winter now, but during the summer I never ran out of water w/these 3 barrels and they fill up really fast!
http://dnr.metrokc.gov/wlr/PI/pdf/covington-rain-barrels.pdf
http://dnr.metrokc.gov/wlr/PI/pdf/covington-rain-barrels.pdf