Of all the second-life uses we ship totes into, rainwater harvesting is the most popular by volume. Every spring we sell a couple hundred Grade C bottles to homeowners, gardeners, market farms, and the occasional landscape architect. The application is good for a tote, good for the user, and good for our circular-economy thesis. But the math people start with is often wrong, and the regulations are not as wide-open as the internet suggests. Here’s a complete field guide.
How much rain can you actually catch
The exact formula is: (roof square footage) × (rainfall in inches) × 0.623 = gallons captured, with a real-world capture efficiency of 75–90% after losses to splash, gutter overflow, and evaporation. The 0.623 constant converts inches of rain over a square foot to gallons.
Some practical numbers: a 1,500-square-foot roof in Northeast Ohio, with average annual rainfall of ~39 inches, theoretically yields ~36,000 gallons. At 80% efficiency that’s ~29,000 gallons, far more than one tote can hold and more than most home garden uses need. The constraint is not annual total — it’s peak storm volume. A single 1.5-inch storm over that same roof yields ~1,400 gallons in an hour, which means you need overflow, period.
Sizing the array
For a productive market-garden operation, our typical recommendation is 4–6 totes linked together with bulkhead fittings at the bottom and a common overflow at the top. This gives you 1,100–1,650 gallons of buffer, enough to cover a typical 10–14 day dry spell during peak growing season. For a homeowner’s ornamental garden, one or two totes is usually enough.
The build
The basic build is straightforward: a first-flush diverter on the downspout, a screened inlet on the top of the tote (mosquito control), a sealed top hatch, a bottom valve fitted with a 3/4″ garden hose adapter or 1″ bulkhead, and an overflow at the top of the tote routed to a rain garden or a daylight outlet.
Pieces we’ve seen people skip and regret: the first-flush diverter (without it, the first 5–10 gallons of every storm carries roof grit and bird waste straight into your supply), the mosquito screen, and the overflow plumbing. The overflow especially: a tote with no overflow that fills to the top during a heavy storm will pop the top hatch, geyser, and possibly knock itself off its base. Always plumb an overflow.
Regulations in OH and MI
Ohio: rainwater harvesting is permitted and lightly regulated. ORC 3701.344 and OAC 3701-28 cover potable use; non-potable use is largely unregulated. If your harvested water touches the interior of the house or is used for any drinking, washing, or food prep, you’re in “private water system” territory and your county health department has rules. For outdoor irrigation only, you’re unregulated as long as you don’t cross-connect to a municipal supply (no shared piping, no submerged fill hoses).
Michigan: similar regime, regulated by the Michigan Department of Environment, Great Lakes, and Energy (EGLE). Outdoor non-potable use is essentially unregulated. Potable use requires a private water supply permit and an annual coliform test.
Both states: you cannot use rainwater harvesting to claim a stormwater fee reduction without a separately approved best-management-practice (BMP) plan in most municipalities. If your goal is utility savings, the irrigation use case usually pays for itself; the stormwater offset usually does not.
What grade tote to buy
Grade C is fine. The water you’re catching has already touched a roof, a gutter, and a downspout; it is not sterile, and any residue inside a rinsed-only Grade C bottle is irrelevant in this application. Save the food-grade premium for applications where it matters.
UV and algae
The single biggest maintenance issue with tote-based rainwater systems is algae growth, which is fueled by sunlight reaching the water. Two solutions: paint the outside of the tote with two coats of exterior latex paint (any opaque color), or wrap the tote in a UV-blocking cover. Painted totes hold up for 6–8 years in our climate before the paint chalks. Black totes are not appreciably better than painted white ones for algae control; what matters is opacity, not color.
Winter
Drain rainwater systems below the bottom valve before the first hard freeze. A tote of water that freezes solid will not crack the HDPE, but it will distort the bottom valve area and shorten the bottle’s life. Leave the valve open all winter so any thaw-water can drain freely.
Questions on this one? Email info@ibctankscleveland.com. We answer everything inside one business day — usually inside four hours.