Why collect rainwater?

Rainwater is the gold standard. Unlike most well water, it has a hardness of zero. This means you'll use less soap on your clothes, dishes and body--and calcium won't collect on your faucets, tiles, glassware and hair. And if you size your system correctly, your rainwater supply is as dependable—if not more dependable--than a well. Unlike most public water supplies, which rely on chlorine for disinfection, rainwater can easily be made safe and potable without the use of any chemicals.

How much rainwater can I collect?

In the real world, where gutters are imperfect and the wind scatters the raindrops, you can collect around 550 gallons for every 1000 square feet of collection surface for every one-inch of rain. To estimate how much you could collect in one year, take the square footage of your collection surface, divide by 1000, multiply by 550 and then multiply by the average annual rainfall for your area.

How much rainwater do I need?

A reasonably conservative person will use between 25 and 50 gallons a day, excluding any landscaping needs. So, a family of four water-wise souls would need around 40,000 gallons per year. You'll want to store enough water to see you through the worst drought on record in your area. Here in the Texas Hill Country, that's around 75 days without rain, which means that family of four would need to store at least 7500.

How much does a system cost?

A modest Tank Town system for a family of four would include one 10,000-gallon fiberglass tank, some type of roof washer or first flush device, a pump, filters and an ultraviolet light. A very ballpark figure for this system would be $10,000-$15,000 installed, not including trenching or gutters. You can trim the cost by doing all or some of the work yourself. You can also spend a lot more loot depending on how complicated your system is.