Why Build a Rain Barrel?

• Save money: Reduce municipal water use during dry spells.
• Protect local waterways: Capturing runoff reduces erosion and stormwater pollution.
• Plant health: Rainwater is soft and free of salts and chlorine, often preferred by plants.
• Emergency supply: Provides non-potable water for cleaning, flushing, and fire-safe landscaping.

Rain barrels are simple: water is routed from your roof’s downspout into a sealed, screened container with a spigot near the bottom for easy access. Overflow is directed safely away during heavy rain.

Planning and Sizing

Estimate Harvestable Water

Formula: Gallons captured ≈ Roof area (sq ft) × Rainfall (inches) × 0.623 × runoff factor (≈0.9)

Example: 500 sq ft of roof and 0.5 inches of rain → 500 × 0.5 × 0.623 × 0.9 ≈ 140 gallons. One standard 55-gallon barrel will fill quickly from even a modest rainfall.

Choose a Barrel

• Capacity: 50–65 gallons is common; consider multiple barrels in series for larger gardens.
• Material: Food-grade, UV-resistant plastic is easiest. Avoid containers that held chemicals.
• Color: Dark/opaque barrels reduce algae growth.
• Top style: Closed-top with bung holes is easiest to seal; open-top requires a secure lid and fine screen.

Check Local Rules

Some regions regulate rainwater harvesting. Verify legality, allowable uses, set-backs, overflow requirements, and mosquito control rules before building.

Materials and Tools

Materials

• 55-gallon food-grade plastic barrel with lid
• 3/4-inch bulkhead fitting or 3/4-inch female tank adapter for spigot
• 3/4-inch brass or PVC hose bib/spigot (garden-hose thread)
• 1–1.5-inch bulkhead fitting for overflow port
• 1–1.5-inch hose or PVC elbow for overflow, plus discharge hose
• Downspout diverter kit or 2x3 or 3x4 inch downspout elbow
• Fine stainless steel mesh or mosquito-proof screen (minimum 1 mm/18-mesh)
• Plumber’s tape (PTFE) and exterior-grade silicone sealant
• Cinder blocks or timber to build a level stand (12–18 inches tall)
• Optional: First-flush diverter kit, leaf filter, union valves, barrel linking kit

Tools

• Drill with hole saws (7/8–1 inch for spigot; 1.5–2 inches for overflow/inlet)
• Step bit, utility knife, and deburring tool or sandpaper
• Adjustable wrench, channel-lock pliers
• Measuring tape, marker, level, safety glasses, gloves

Cost and Time

• Estimated cost: $50–$150 per barrel (varies by barrel source and fittings)
• Build time: 2–4 hours for a first build

Step-by-Step Build

1) Prepare the Barrel

1. Clean thoroughly: Rinse and scrub inside. If it held food (e.g., olives), use a baking soda solution to remove residues and odors.
2. Plan layout: Mark spigot hole about 2–3 inches above the bottom (to avoid sediment), overflow port near the top side, and inlet on the lid/top.

2) Install the Spigot

1. Drill the spigot hole using the appropriate hole saw for your bulkhead fitting.
2. Deburr the hole edges for a clean seal.
3. Install the bulkhead from the inside (gasket inside the tank) and tighten the outside nut snugly by hand, then gently with pliers. Do not overtighten.
4. Wrap PTFE tape on the spigot threads and screw into the bulkhead. Orient the outlet downward. Hand-tighten plus an extra quarter-turn.

3) Add the Overflow

1. Drill a hole near the top side of the barrel for the overflow bulkhead (1–1.5 inches).
2. Install the bulkhead and attach an elbow pointing away from structures.
3. Connect a hose or pipe to route overflow to a safe drainage area, rain garden, or secondary barrel.

4) Create the Inlet and Screen

1. Closed-top barrels: Drill an inlet hole on the lid to match your diverter or downspout elbow. Open-top barrels: Ensure the lid accommodates a taut, fine mesh screen.
2. Secure the screen over the inlet with a retaining ring, screws with a clamping band, or a diverter that includes a built-in filter. The screen must exclude mosquitoes and debris.

5) Seal and Test

1. Apply a thin bead of exterior silicone around fittings if needed.
2. Fill the barrel partially with a hose to check for leaks at the spigot and overflow. Tighten gently if required.

6) Prepare the Stand

1. Level the ground and lay pavers or a compacted gravel base.
2. Stack cinder blocks or build a timber platform. Ensure it’s stable and level—the filled barrel can weigh 400–500 lbs (180–225 kg).

Placement and Setup

• Near a downspout: Choose the closest downspout to your garden.
• Elevate the barrel: Height increases pressure and makes it easier to fill watering cans. Aim for 12–24 inches.
• Connect the diverter: Install a downspout diverter at the manufacturer’s recommended height. It directs water in when the barrel has capacity and returns flow to the downspout when full.
• Overflow routing: Direct overflow onto permeable surfaces or a rain garden—never toward foundations or neighbors.
• Sun and algae: Shade reduces algae, but access matters more. An opaque barrel mitigates algae growth even in sun.

How to Use the Water

Best Uses

• Watering ornamental beds, trees, shrubs, and lawns
• Vegetable gardens—apply to soil, not edible leaves; avoid pre-harvest foliar contact
• Tool and patio rinsing (non-potable)

Delivery Options

• Gravity feed: Connect a hose to the spigot. Works best with soaker hoses and gentle slopes.
• Watering can: Place the barrel high enough to fit a can under the spigot.
• Pump assist: A small 12V or AC transfer pump gives hose-spray pressure and supports drip irrigation.
• Drip/soaker systems: Use pressure-compensating drip emitters designed for low pressure or add a pump and filter (100–200 mesh) to protect emitters.

First-Flush and Filtration

• Leaf screen: At gutter or diverter to catch large debris.
• First-flush diverter: Captures the initial roof wash-off (dust, bird droppings) to improve water quality for garden use.
• Mesh screen: Required at inlet to block mosquitoes.

Maintenance and Winterizing

Routine Care

• Inspect monthly during rainy season: check screens, seals, and overflow routing.
• Clean inlet screen and diverter filters as needed.
• Flush sediment every few months by opening the spigot and gently agitating the barrel.
• Keep the lid tight and screens intact to prevent mosquitoes and algae.

Winterizing (Freezing Climates)

• Drain the barrel completely and leave the spigot open.
• Disconnect the diverter or set it to bypass the barrel.
• Store the barrel upside-down or indoors to avoid freeze damage.
• Ensure overflow and downspouts are clear to handle winter rains/snowmelt.

Safety, Health, and Legal Notes

• Non-potable: Do not drink rain barrel water without proper treatment. Keep “Non-Potable Water” labels visible.
• Stability: Place on a level, strong base. Secure in windy areas and keep away from pathways where it may be bumped.
• Child and pet safety: Keep lids secured; never leave open water that could pose a drowning risk.
• Mosquito control: All openings must be screened. Consider BTI mosquito dunks if needed (safe for gardens when used as directed).
• Roof materials: Avoid harvesting from roofs with copper, lead, or treated wood shingles. Asphalt and composite shingles are generally fine for ornamental watering; for edibles, water soil only and consider first-flush.
• Local codes: Comply with any regional restrictions, permitting, or overflow requirements.

Troubleshooting and Upgrades

Common Issues

• Leak at spigot/overflow: Check gasket orientation, avoid overtightening, add PTFE tape, and reseal with silicone if necessary.
• Slow flow: Raise the barrel higher, shorten hose length, use larger-diameter hose, or add a pump. li>
• Algae growth: Use opaque barrels, keep lid on, add shade, and clean quarterly.
• Mosquitoes present: Repair torn screens, seal gaps, add BTI dunks.
• Barrel bulging: Avoid overfilling with sealed systems—ensure a functional overflow. Inspect for sun damage or material fatigue.

Useful Upgrades

• Multiple barrels in series: Connect overflows at the top for equalizing, or daisy-chain from the first barrel’s overflow to the next inlet.
• Automatic irrigation: Timer + pump + drip lines with a filter and pressure regulator.
• Water level gauge: Clear tubing level indicator or a float gauge to check volume at a glance.
• Backflow prevention: If connecting to any pressurized system, use an air gap or approved backflow preventer.
• Decorative cladding: Hide barrels with lattice or planters while keeping access for maintenance.

FAQ

How much pressure does a rain barrel provide?

About 0.43 psi per foot of elevation. A barrel raised 2 feet provides roughly 0.86 psi—enough for short hoses or soaker hoses, but not for sprinklers without a pump.

Is rain barrel water safe for vegetables?

Generally acceptable for soil watering if your roof materials are garden-safe (avoid copper/lead). Use a first-flush diverter, avoid wetting edible leaves, and stop overhead watering 1–2 weeks before harvest. If uncertain, consider lab testing or use for ornamentals only.

Do I need a first-flush diverter?

Not required, but recommended. It improves water quality by diverting the initial roof runoff that can contain debris and contaminants.

What about mosquitoes?

Use fine mesh screens on all openings, keep the lid on, maintain seals, and add BTI dunks if necessary.

How do I connect to a downspout?

A diverter kit is the easiest and cleanest method. It also prevents overfilling by sending excess water back down the downspout once the barrel is full.

Can I paint the barrel?

Yes. Lightly sand, prime with a plastic-bonding primer, and use UV-resistant exterior paint. Dark colors inhibit algae.

Wrap-Up

A DIY rain barrel is a practical, low-cost way to reduce water bills, support a healthier garden, and manage stormwater. With proper planning, secure fittings, and regular maintenance, your system will provide years of reliable, eco-friendly irrigation. Start with one barrel, then expand as your garden and confidence grow.