Rainwater Harvesting

The math is smaller than the barrel aisle suggests

Every rainwater setup starts with one formula: your roof collects about 0.62 gallons per square foot per inch of rain. A 1,000 sq ft roof in a one-inch storm sheds roughly 620 gallons — which is why a single 50-gallon barrel overflows in the first twenty minutes, and why the right question isn't "should I get a barrel" but "how much storage does my roof and climate justify." The catchment math guide works the formula with a reference table by roof size, so you can size storage before you buy it.

Buy the diverter before the second barrel

The unglamorous parts do the real work. A downspout diverter sends overflow back to the drain instead of your foundation; a first-flush diverter dumps the initial dirty runoff that carries most of the roof's dust, pollen, and bird droppings; a screen keeps mosquitoes from turning the barrel into a nursery. The barrels and diverters guide covers the picks by setup size, from a single barrel to linked IBC totes.

Common questions

Can I drink collected rainwater? Treat roof water as non-potable by default — garden, lawn, and washing uses are the safe lane. Roofing materials, gutters, and everything that lands on the roof end up in the water, and making it drinkable is a filtration-and-disinfection project, not a barrel purchase. The safety guide covers the contaminants, first-flush and filtration, and why testing and local rules decide the answer.

Is collecting rain even legal where I live? In most US states, yes, and several actively encourage it — but a few regulate volume or method, so check your state and city rules before plumbing anything permanent.

When does a system pay for itself? Fastest where water is priced steeply in summer and gardens are thirsty: a few hundred gallons of storage refilled by a dozen summer storms replaces a meaningful slice of peak-rate irrigation. In wet climates, the win is less about the bill and more about soft, chlorine-free water your plants prefer.