This week's poll has to do with what people want to use rainwater collection for, whether it be watering lawns or running the commode. Even ambitious LIDers won't be using rainwater to wash clothes anytime soon b/c they don't have dual plumbing systems (potable/non-potable) in their homes. So that leaves most us looking at outside uses, watering the lawn and the like.
Rain barrels are becoming more and more popular. But it seems the minute most people put one in they want it bigger: a 55-gallon barrel doesn't go very far. How far you might ask? Well, I use a 55-gallon barrel for air conditioner condensate collection and am able to water my container plants for about week from one barrel. How much water do you need?
A traditional lawn needs about 1-inch of water per week during the summer. That's 0.623 gallons per week per square foot. (Sometimes I just call it a half-gallon per foot to make it easy.) If you have a lawn that is 20' x 50', that's 1,000 square feet of lawn. It would take 623 gallons of water per week. During the summer, let's say that it doesn't rain for a month. Over those four weeks your lawn would need 4 x 623 gallons = 2,480 gallons. If your lawn is bigger, you'll need more, maybe much more!
So, here's where reason kicks in. Are you ready for a 2,500 gallon (or larger) tank? Do you have the space? (A 2,500 gallon-tank is about 8 feet in diameter and 7 feet tall.) Does your neighborhood allow these kinds of appurtenances?
There are a number of factors to consider when evaluating "How Much is Enough?". Maybe for you it is a rain barrel to refill the fish pond, maybe it's finding out if the old cistern in the backyard still holds water, or maybe its having a system engineered for your specific needs. Whatever you decide, there's an opportunity every time the rain falls.
