Starting a Rain Barrel

Why Collect Rainwater? At a Glance

The math is simple but striking: a 1,000-square-foot roof sheds approximately 600 gallons of water per inch of rainfall. A single 1.5-inch rain event — not unusual anywhere in the United States — produces 900 gallons from that roof alone. A standard 55-gallon rain barrel captures what falls on about 90 square feet of that roof; a pair of linked barrels captures twice as much. A modest cistern system captures thousands of gallons from a single storm.

Rain barrels represent one of the most accessible sustainable home improvements available — they require no special skills, a modest investment of $30 to $200 for a basic setup, and produce tangible, measurable results immediately. They are also a gateway into a broader understanding of how water moves through residential landscapes and how thoughtful design can keep more of that water on-site and working for the garden.

Section 1: The Legal Landscape — State Laws, Restrictions & Rebates

Rainwater collection law in the United States is a patchwork of state-by-state regulation that reflects the very different water law traditions of the eastern and western halves of the country. In most of the East, rainwater collection is unregulated and often encouraged. In some western states, it has historically been prohibited or restricted under prior appropriation water law — though this is changing rapidly as drought concerns drive policy reform. Before installing a rain barrel system, it is your responsibility to understand your state's current regulations.

The Water Law Divide: East vs. West

Eastern water law is generally based on riparian rights — the principle that landowners have the right to use water that flows through their property. In this framework, collecting rainwater that falls on your roof is simply using water already on your property and is unrestricted in most eastern states. Western water law is generally based on prior appropriation — the principle that water rights are established by historical use and belong to specific rights-holders rather than to the landowner. Under strict prior appropriation doctrine, rainwater falling on your property was historically considered part of a stream's water supply and "belonged" to downstream water rights holders. This doctrine led several western states to prohibit or severely restrict residential rainwater collection for much of the 20th century. However, the ongoing western drought crisis has driven significant legislative reform since the early 2000s, and most western states now permit residential rainwater collection with varying limits.

Rebates, Incentives & Subsidized Programs

In addition to state law, many local water utilities, municipalities, and regional water authorities offer financial incentives to encourage residential rainwater collection. These programs vary enormously by location and change frequently, but can dramatically reduce the cost of installation.

• •Cash rebates: Many utilities offer cash rebates per barrel installed (often $50–$100) or per gallon of storage capacity added. Southern California water agencies, Tucson Water, Denver Water, and many Texas water utilities have active rebate programs. Check your water utility's conservation program website first.
• •Subsidized or free barrel programs: Many municipalities partner with local suppliers to offer rain barrels at a steep discount (often $20–$40 for a barrel that retails for $80–$120) through a one-day distribution event or ongoing program. Search "[your city] rain barrel program" to find current offerings.
• •Tax incentives: New Mexico offers a tax deduction for qualified rainwater harvesting systems. Texas exempts rainwater harvesting equipment from sales tax. Oregon has offered tax credits for larger systems. Check your state revenue department for current programs.
• •HOA protections: Several states including Texas, California, Colorado, and Florida have passed laws preventing HOAs from prohibiting rainwater collection systems. If you live in an HOA, check your state's current law before assuming a prohibition is enforceable.

Section 2: How Much Water Can You Collect?

Understanding your potential collection volume is the foundation of system design. It tells you how large your storage needs to be, whether a single barrel is sufficient or whether a cistern is warranted, and how much of your garden irrigation need can realistically be offset by harvested rainwater.

The Collection Formula

The amount of water collectible from a roof is determined by three variables: the rainfall amount, the roof area draining to the collection point, and a collection efficiency factor that accounts for evaporation, splash, and first-flush losses.

Roof Area Calculation

You don't need to measure your roof directly. The "footprint" — the horizontal area it covers, measured from the eaves, not along the slope — is what determines collection. Measure the outside dimensions of your house at ground level and multiply length by width for a rectangular home. For L-shaped or more complex footprints, break it into rectangles and sum them. Then divide the total footprint by the number of downspouts to estimate what each downspout serves.

• •In a typical 1,500 sq ft ranch-style home with four downspouts, each downspout drains approximately 375 sq ft.
• •In a 2,500 sq ft two-story home with six downspouts, each drains about 415 sq ft.
• •Garage and outbuilding downspouts can be excellent collection points: the roof is often simpler (one or two downspouts draining the full footprint), the drainage area is clean, and the location is convenient for a garden barrel.

Annual Rainfall by Region: Collection Potential

How Much Do You Need? Matching Storage to Use

Section 3: Choosing Your Rain Barrel

Rain barrels range from a repurposed 55-gallon food-grade drum to a decorative urn-style barrel to a professional 100-gallon barrel with integrated first-flush diverter. The right choice depends on your collection goals, the aesthetics of your setting, your budget, and whether you are buying a ready-made product or assembling your own from components.

Commercial vs. DIY Rain Barrels

Key Features to Look For in a Rain Barrel

• •Closed, screened lid: The lid must be fully sealed or screened to prevent mosquito breeding. Aedes albopictus (Asian tiger mosquito) can complete its life cycle in as little as a week in standing water — an unscreened rain barrel becomes a mosquito hatchery within days in warm weather. The screen mesh must be fine enough to exclude mosquitoes (1/16-inch mesh minimum; finer is better). Commercial barrels almost always include appropriate screens; DIY barrels require fitting a screen over any opening.
• •Overflow port at or near the top: When the barrel is full, water must go somewhere controlled. An overflow port near the barrel's top, fitted with a hose or tube that directs overflow away from the foundation, is essential. Without it, overflow will run down the side of the barrel and pool against the foundation — the exact problem a functioning downspout was preventing.
• •Spigot positioned for gravity drainage: The spigot should be positioned as close to the bottom of the barrel as possible for maximum drainage volume. However, it also needs to be high enough off the ground that a watering can or hose fits underneath it — 3–4 inches of clearance is minimum; 6–8 is better. An elevated barrel platform solves both problems.
• •UV-resistant material: Barrels placed in outdoor sunlight must be made of UV-resistant polyethylene or similar material. Non-UV-treated plastic becomes brittle within 1–2 years in direct sun. Most commercial rain barrels are UV-stabilized; verify this when purchasing. Alternatively, paint a DIY barrel with exterior latex paint to provide UV protection.
• •Food-grade material: Even though rainwater collected for garden irrigation does not need to be potable, using food-grade barrels (previously used for food-grade liquids) ensures no leaching of industrial chemicals. Look for the recycling symbol with the number 1 (PETE), 2 (HDPE), or 5 (PP) — all food-safe. Avoid barrels previously used for chemicals, herbicides, or industrial solvents, even if apparently clean.

Single vs. Linked Barrel Systems

A single 55-gallon barrel fills quickly in a significant rain event and then provides no additional collection for the remainder of the storm. Linking two or more barrels in series dramatically increases storage capacity and slows the rate at which you overflow during large events. The math is simple: two linked 55-gallon barrels double the capture volume of a single barrel and more than double the effective capture for any event larger than 0.2–0.3 inches of rain.

• •Parallel linking (barrels fill simultaneously): Connect a T-fitting at the overflow port so that as the first barrel fills, overflow goes into a second barrel at the same level. Both barrels receive water simultaneously if the inlet is split; more commonly, barrels are linked at the overflow port so the first fills, then overflow feeds the second. Both methods work; the overflow-linked method is simpler.
• •Practical limit for linked barrels: Three to four standard barrels linked in series is typically the practical limit before plumbing complexity and the structural challenge of building a level, stable platform for multiple heavy barrels becomes a reason to consider a larger single tank instead.

Section 4: Installation — Step by Step

A standard rain barrel installation takes 2 to 4 hours for a first-time installer. The most technically demanding part is modifying the downspout; the rest is positioning, plumbing, and testing. The tools required are basic: a drill, a utility knife or hacksaw, a level, and basic plumbing fittings.

Tools and Materials

• •Tools needed: Drill with 1-1/8 inch spade bit (for spigot hole in DIY barrel); utility knife or jigsaw for downspout modification; hacksaw for PVC pipe (if building a first-flush diverter); tape measure; pencil; level; adjustable wrench; Teflon tape.
• •Materials for a complete basic installation: The barrel itself; a downspout diverter or diverter kit; a spigot / brass or PVC hose bib (for DIY barrels); a grommet or silicone sealant for the spigot fitting; an overflow hose or fitting and extension; Teflon thread tape; mosquito screening (if not included); lumber or cinder blocks for a platform (optional).

Step-by-Step Installation

• •Choose your location: Select the downspout that drains the largest roof area and is closest to your primary garden use area. The barrel must be on firm, level ground — a full 55-gallon barrel weighs 458 pounds and will tip over or sink into soft ground if improperly placed. Check that the location allows for the overflow hose to direct water away from the foundation (ideally 6 feet or more from the house).
• •Build the platform (optional but recommended): A platform of stacked concrete blocks, a commercial rain barrel stand, or a simple frame of 4×4 lumber raises the barrel 12–24 inches, creating gravity pressure at the spigot and making it easier to fill a watering can underneath. Ensure the platform is level in all directions before placing the barrel. A full barrel on an unlevel platform will tip. Use a level on all sides.
• •Prepare the downspout: Most installation methods involve either (a) a downspout diverter — a T-fitting inserted into the downspout that redirects flow to the barrel when it is below capacity and continues to the original drainage path when the barrel is full; or (b) cutting the downspout and directing the cut end directly into the barrel inlet. Option (a) is reversible and preferred for most installations.
• •Install the downspout diverter: Measure and mark the diverter location on the downspout. The diverter must be positioned so the outlet that connects to the barrel is at or above the height of the barrel's inlet. Use a utility knife, tin snips, or a jigsaw to cut the downspout at the marked line. Insert the diverter following the manufacturer's instructions; secure with the provided screws or clips. Connect the diverter's barrel outlet to the barrel inlet with the flex hose or tubing provided.
• •Install the spigot (DIY barrels only): Drill a hole near the base of the barrel using the appropriate spade bit for your spigot's thread diameter (usually a 1-1/8 inch bit for a 3/4-inch hose bib). Apply Teflon tape to the spigot threads. Insert the spigot through the hole from the outside and thread the interior nut or backing fitting tight against the barrel wall. Use silicone sealant around the fitting to prevent leaks; allow to cure 24 hours before filling.
• •Install the overflow fitting: Insert or drill a hole for the overflow port near the top of the barrel (2–4 inches below the rim, or at the rim if the lid is sealed). Attach a 1-inch or larger overflow hose fitting. Extend the overflow hose or pipe to direct overflow at least 4–6 feet away from the foundation, ideally toward a garden bed, rain garden, or lawn area where the water will be absorbed rather than running off.
• •Ensure the lid is secured and screened: The lid must be in place and secured before the first use. Check that all gaps, inlet openings, and the overflow port outlet are screened with fine-mesh screen (mosquitoes can enter through the overflow hose and lay eggs if the outlet end is not screened or dipped in water). For DIY barrels with an open top, cut a piece of fiberglass window screen to fit and secure with a bungee cord or cut-and-press-fit ring.
• •Test the system: Run a hose into the gutter above the downspout diverter, or wait for rain. Check: water flows into the barrel correctly; no leaks at the spigot or overflow fittings; the overflow hose directs water away from the foundation; the lid remains in place and screened when the barrel fills and water pressure builds inside. Adjust as needed.

Downspout Diverter Options

Section 5: First Flush Diverters & Water Quality

The quality of harvested rainwater depends enormously on what it washes off the roof before reaching the barrel. The first flow of water from a roof after a dry period carries accumulated bird droppings, dust, atmospheric pollutants, pollen, leaf debris, and roof material residue. This "first flush" water is the most contaminated portion of any rainfall event. A first-flush diverter automatically discards this initial volume and only sends cleaner subsequent flow into storage.

What's in Roof Runoff?

Rainwater arriving at your barrel has passed over the roof surface, through the gutter, and down the downspout. Each stage adds potential contaminants:

• •Atmospheric deposition: Dust, pollen, particulates, and atmospheric pollutants settle on the roof between rain events. The first flush washes most of these off. Rainwater in areas near industrial sites, highways, or agricultural operations with pesticide application may carry higher atmospheric contamination.
• •Roof material: Asphalt shingles can leach polycyclic aromatic hydrocarbons (PAHs) and zinc from metal flashings. Treated wood shakes historically leached preservatives. Copper roofing and gutters can elevate copper levels. Galvanized metal roofing can elevate zinc levels. For ornamental garden irrigation (not vegetables, not edibles, not lawns where children play), these levels are generally not a concern. For vegetable garden irrigation, the scientific evidence is mixed; many studies show levels below EPA thresholds after the first flush.
• •Biological contamination: Bird and squirrel droppings on roofs are the primary source of biological contamination in roof runoff. Salmonella and other pathogens from droppings can be present, particularly in the first flush. Studies consistently show that first-flush diversion and allowing water to settle dramatically reduces biological contamination in stored water.
• •Lead: Older homes with lead-soldered gutters or lead-based painted eaves may have elevated lead in roof runoff. Inspect gutters and fascia on older homes; replace lead-soldered gutters before installing a collection system.

The First-Flush Diverter: How It Works

A first-flush diverter is a simple device — most commonly a standpipe of PVC pipe — that fills with the initial dirty flow from the roof before the cleaner water reaches the storage barrel. Once the standpipe is full, overflow into the barrel begins. When rain stops, the standpipe slowly drains through a small orifice or ball valve, clearing it for the next rain event.

• •Sizing the first-flush volume: The standard recommendation is to divert the first 10 gallons per 1,000 square feet of roof area (or approximately 0.016 inches of rainfall times the roof area draining to that downspout). For a downspout serving 500 square feet of roof, divert the first 5 gallons — approximately 32 inches of 4-inch PVC pipe.
• •Commercial first-flush diverters: Available in several designs; typically $20–$50. They integrate with the downspout above the barrel inlet and include a self-cleaning ball or float mechanism. Follow manufacturer instructions for sizing to your roof area.
• •DIY first-flush diverter (PVC): The simplest DIY design uses 4-inch PVC pipe as the standpipe, a 4-inch Y-fitting at the top to connect to the downspout, a 4-inch end cap at the bottom of the standpipe with a small hole (1/4 inch) drilled through it to allow slow draining, and a T or Y fitting at the standpipe-to-barrel connection point. This is a straightforward PVC plumbing project requiring basic skills and a pipe cutter.

Water Quality by Intended Use

Section 6: Using Your Stored Water

The most common frustration with rain barrels is low water pressure. A standard rain barrel sitting at ground level produces essentially no usable gravity pressure at the spigot — water will dribble rather than flow with the force needed to fill a watering can quickly or run a soaker hose. Understanding gravity pressure, elevation, and the solutions to low pressure transforms the rain barrel from a curiosity into a genuinely productive irrigation tool.

Gravity Pressure: The Physics

Water pressure in a gravity-fed system is determined entirely by the height difference (head) between the water surface in the barrel and the outlet point. The relationship is direct: every foot of elevation above the outlet produces 0.43 PSI (pounds per square inch) of water pressure.

Delivery Methods

• •Watering can: The simplest and most controlled method. Fill directly from the spigot. Works at any elevation but is slow at ground level. Best for targeted hand-watering of containers and individual plants.
• •Garden hose (gravity): A standard garden hose connected to the barrel's spigot works at low pressure but delivers water much more slowly than from a municipal supply. Use a hose with the nozzle removed or set to open flow; sprinkler nozzles and hose-end sprayers require more pressure than gravity barrels can typically provide. Drip the hose at the base of plants; it works well for slow, deep watering.
• •Soaker hose: Soaker hoses are specifically designed for low-pressure operation and pair well with rain barrels at 12–36 inches of elevation. Run soaker hoses along plant rows; connect to the barrel spigot with a short length of regular hose. Keep runs short (50–100 feet maximum for gravity-only pressure) for even distribution.
• •Drip irrigation: Standard drip irrigation emitters typically require 8–15 PSI — far above what a gravity barrel provides. Low-pressure or gravity-fed drip emitters (specifically labeled as such, requiring as little as 2–3 PSI) are available and work with elevated barrels. These are an excellent long-term investment for a garden irrigation system fed from a rain barrel or cistern.
• •Pump-assisted delivery: A small submersible pump (12V DC solar-powered pumps are ideal for rain barrel applications; small AC pumps also work) placed inside the barrel and connected to a standard hose or drip system provides full irrigation pressure regardless of barrel elevation. A 12V solar pump with a small solar panel costs $30–$80 and provides completely independent, electricity-free operation.

Keeping Stored Water Healthy

• •Use it regularly: The single most effective practice. Water used frequently is replaced by fresh rainfall, preventing long-term stagnation. A barrel that sits full all summer while the garden is watered from the hose provides no benefit and may develop water quality issues. Use the barrel water first, before reaching for the hose.
• •Keep the barrel shaded: Algae require light. An opaque barrel blocks light and prevents algae growth. For translucent or light-colored barrels, shade with a burlap cover, wooden screen, or plant material. Alternatively, wrap in a dark fabric or paint the exterior.
• •Refresh stagnant water: If the barrel sits full for more than 2–3 weeks in summer without being used or replenished by rain, drain it partially onto the garden (the water is still excellent for irrigation even if the barrel smells slightly stale) and allow fresh rain to refill it.
• •Bti dunks for larval control: One Bti mosquito dunk treats 100 gallons for 30 days and kills any mosquito larvae present without harming other organisms. Add a dunk as a precaution during summer even when screens appear intact. Break the dunk in half for a 55-gallon barrel.

Section 7: Winterizing & Seasonal Care

In climates where temperatures drop below freezing, a rain barrel left full or partially full through winter will freeze, expand, and crack the barrel, split fittings, and damage the entire installation. Winterization is mandatory for any climate in Zones 6 and colder (where freezing temperatures are reliably present for extended periods), and advisable in Zone 7 where hard freezes occur occasionally.

When to Winterize

Winterization Procedure

• •Use the water: In the weeks before winterizing, use down your stored water on the garden, compost, or lawn. It is better irrigation than tap water and costs nothing to use.
• •Disconnect the downspout: Reconnect the original downspout section (or close the diverter) so winter rain and snow melt flows through the original drainage path rather than into your barrel. This prevents the barrel from filling during freeze/thaw cycles.
• •Drain the barrel completely: Open the spigot fully and drain all water. Tip the barrel slightly if needed to drain the last few inches. Turn the barrel upside down if possible to ensure complete drainage.
• •Remove and store fittings (optional but recommended): The spigot, overflow fitting, and any flexible hose connections are the most vulnerable to freeze damage. Remove them and store indoors for winter. Plug the holes with a rubber stopper or rag to prevent insects from nesting in the empty barrel.
• •Store the barrel: If possible, store the barrel upside down in a garage, shed, or under an overhang. Stored upside down, it cannot collect rain or snow melt and will not freeze-crack. If the barrel must remain outside in place, leave the spigot open (so any water that enters can drain) and secure the inverted or unsealed lid so it cannot blow away.
• •Inspect in spring: Before reactivation, inspect the barrel for cracks, loose fittings, and screen integrity. Replace any damaged components before the first use of the season.

Spring Reactivation

• •Clean the barrel: Before the first use of the season, rinse the interior with clean water and a mild soap solution; rinse thoroughly. Check the screen for tears or gaps; repair or replace.
• •Inspect and reinstall fittings: Apply fresh Teflon tape to spigot threads; reinstall fittings snugly. Check all gaskets and seals; replace if the rubber has hardened or cracked.
• •Check the overflow path: Make sure the overflow hose is intact and positioned to direct water away from the foundation. Check that the downspout diverter is properly reconnected.
• •Reconnect to the downspout: Open the diverter or reconnect the downspout to the barrel inlet. The system is ready to collect the first spring rain.

Section 8: Troubleshooting Common Problems

Section 9: Scaling Up — Cisterns, Tanks & Advanced Systems

Once the rain barrel is installed and working, many gardeners reach the same conclusion: they want more. A single barrel fills quickly, empties quickly, and leaves the majority of the rooftop runoff potential untapped. Scaling up to cisterns and more sophisticated collection systems is the logical next step for gardeners serious about reducing their irrigation water footprint.

Storage Tank Options Beyond the Barrel

Designing a Multi-Barrel or Cistern System

• •Multiple downspout collection: Rather than collecting only from the nearest downspout, a more sophisticated system collects from multiple downspouts around the house and routes water to a central storage tank. This requires underground or above-ground piping to connect multiple collection points, which is a plumbing project requiring some planning but no specialized skills.
• •Gravity-fed distribution from an elevated tank: An IBC tote or above-ground cistern elevated 3–5 feet (on a reinforced concrete pad or heavy structural platform) provides meaningful gravity pressure for drip irrigation. The weight of a full 275-gallon IBC tote is 2,290 pounds — the platform must be engineered accordingly.
• •Pump-fed distribution: A small electric pump (submersible or inline) converts a low-pressure gravity system into a full-pressure irrigation supply. A 1/2 HP submersible pump costs $100–$200 and can pressurize a full drip irrigation system from a ground-level cistern. Pair with a timer and a simple drip system for automated, harvested-water irrigation.
• •First flush at scale: At larger collection volumes, a first-flush diverter becomes more important. For a 275-gallon IBC tote collecting from multiple downspouts, a proportionally larger first-flush standpipe (or multiple downspout-level diverters) ensures that stored water quality is consistently good.

Permits and HOA Considerations for Larger Systems

While a standard 55-gallon rain barrel typically requires no permit anywhere in the US, larger cisterns and underground tanks may trigger local requirements:

• •Building permits: Underground cisterns (typically any tank buried in the ground) may require a building permit in many jurisdictions. Above-ground cisterns over a certain size (varies by municipality, often 500–1,000 gallons) may also require permits. Check with your local building department before installing any large tank.
• •HOA restrictions: If you live in a community with an HOA, check the CC&Rs for restrictions on above-ground structures or water storage tanks. Many states now prohibit HOAs from banning rain barrels entirely, but restrictions on visible larger tanks may still be enforceable. Concealing an IBC tote with a wooden enclosure or lattice is a practical solution where visibility is restricted.
• •Structural considerations: Any water storage system above ground must have an adequately rated structural base. A full IBC tote (275 gallons = 2,290 lbs) on an inadequate surface can fail catastrophically. Underground cisterns require proper backfill and may require anti-flotation measures in areas with high groundwater.

Section 10: The Ecological Context — Beyond the Barrel

A rain barrel is a useful tool, but it is most powerful when understood as part of a broader approach to managing how water moves through your property. The larger ecological opportunity is to slow water down, spread it out, and let it sink in — rather than channeling all precipitation off the property as quickly as possible through engineered drainage systems designed for exactly the opposite goal.

The Stormwater Problem

In a natural landscape, a significant rainfall event infiltrates into the soil, is taken up by vegetation, and slowly percolates toward groundwater or moves as shallow subsurface flow toward streams. In a developed residential landscape, typically 50 to 70 percent of the same rainfall becomes immediate surface runoff that carries pollutants into storm drains and overwhelms streams with sudden peak flows that cause flooding and erosion.

A rain barrel intercepts a small fraction of that runoff. The real ecological leverage comes from combining the rain barrel with landscape practices that keep more water on-site: rain gardens, permeable paving, bioswales, and strategic grading that directs overflow toward planted areas rather than toward impermeable surfaces and storm drains.

Complementary Practices

• •Rain gardens: A planted depression in the landscape, positioned to receive overflow from the rain barrel (and from the rest of the downspout during large events), that holds water long enough to percolate into the soil rather than running off the property. A rain garden sized to capture a 1–2 inch rain event from its contributing area typically drains within 24–48 hours. It is not a pond; it is a planted infiltration basin. Combined with a rain barrel, the rain garden handles the overflow that the barrel cannot capture.
• •Permeable paving: Replacing impermeable concrete or asphalt driveways, paths, and patios with permeable pavers, gravel, or pervious concrete allows rainfall to infiltrate where it falls rather than running off. Permeable paving combined with rain barrels can capture the majority of a rain event from a residential property.
• •Strategic grading: Simple grading changes — sloping yard areas toward planted beds rather than toward paved surfaces; creating gentle swales that slow and spread runoff; building berms that hold water in place — can dramatically increase on-site infiltration without any plumbing or structures.
• •Sheet mulching: Maintaining 3–4 inches of organic mulch over all planted areas reduces runoff velocity, increases infiltration, and reduces soil evaporation — keeping more of the rain that does fall in place where it can benefit plants.
• •Native and deep-rooted plantings: Native plants with deep root systems create channels for water infiltration that dramatically exceed the infiltration rate of turf grass. A deep-rooted native prairie planting or native woodland garden captures and infiltrates far more rainfall per square foot than any lawn.

Calculating Your Impact

A single 55-gallon rain barrel, used consciously through a growing season, can save 1,000 to 2,000 gallons of municipal water annually — a meaningful but modest amount. The impact grows with each additional barrel, each linked cistern, each rain garden installed downstream of the barrel's overflow. A household that combines a 200-gallon cistern system with a 300-square-foot rain garden and strategic grading can retain and use 20,000 to 40,000 gallons of rainfall annually that would otherwise have flowed into the storm drain — a contribution to stormwater management that is genuinely significant at the watershed level when replicated across a neighborhood.

Quick Reference Checklist

• •Verify your state's rainwater collection laws and any local ordinances
• •Check your water utility and local municipality for rebates or subsidized barrel programs
• •Identify the best downspout location (largest roof area, closest to garden)
• •Calculate collection potential: Rainfall × Roof Area × 0.623 × 0.85
• •Choose barrel type and size appropriate to garden irrigation needs
• •Acquire materials: barrel, diverter, spigot, overflow fitting, screen, platform materials
• •Build elevated platform (12–24 inch minimum; ensure it is level and load-rated)
• •Modify downspout with diverter kit
• •Install overflow hose directed 4–6 feet from foundation
• •Verify all openings are screened (inlet, overflow outlet, any vents)
• •Install first-flush diverter if using water on edibles
• •Test system with a garden hose before the first rain event
• •Add a Bti mosquito dunk to water during warm months
• •Plan winterization (drain before first hard freeze in Zones 3–7)
• •Use stored water regularly; don't let it sit for more than 2–3 weeks in summer