Wherever you have Acid rain,Dirty water will be coming from the sky,So one would not be collecting in those locations!I think it was El Nino that,Actually gave So.Cal, The Statistical 14" of rain,Other than that,It rained last Thursday night into Friday,1st Real Rain,I've seen in Months!It would take a Solid Week of Rain,to Clean the Roofs off,Here in The Dirty Basin,Probably longer for The Filthy&Smoggy San Fernando Valley!Anyone who's lived here Know's,It's Very Rare to have,Even a Solid day of Rain!Without an Infrastructure in Semi-Decent condition,It's not too practical,for everyone to collect water! But it Certainly is a Great idea! I say No Running water for Jail/Prisons,That would save trillions of gallons,Alone!