How to Install a Rain Barrel: Downspout, Overflow, and Placement

A single inch of rain falling on a 1,000-square-foot roof produces roughly 600 gallons of water. Capturing even a fraction of that with a rain barrel slashes your summer watering bill and reduces stormwater runoff. When you install a rain barrel, you are setting up a simple gravity-fed system that collects roof runoff and stores it until your garden needs it. The setup costs $30 to $120 and takes about an hour.

Choosing the Right Rain Barrel

Rain barrels range from basic repurposed 55-gallon drums to decorative models that look like planters or stone urns. Key features to compare:

• Capacity: 50 to 65 gallons is standard. A 55-gallon barrel fills up in about 20 minutes during moderate rainfall from a typical residential downspout
• Material: Food-grade HDPE plastic is the most common and affordable ($30 to $80). Wooden whiskey barrel styles cost $80 to $150. Avoid barrels that previously held chemicals
• Spigot: Look for a brass spigot rather than plastic. Brass threads last longer and seal better. Position matters — a spigot 4 to 6 inches from the bottom allows you to place a watering can underneath
• Screen: A fine mesh screen on top keeps mosquitoes, leaves, and debris out of the barrel
• Overflow port: Essential for directing excess water away from your foundation when the barrel is full

Popular models include the RTS Home Accents 50-Gallon ($90 to $110), the Good Ideas Rain Wizard ($80 to $100), and budget-friendly plain drum conversions available at farm supply stores for $30 to $50.

Selecting the Best Location

Placement determines how well your rain barrel performs and how easy it is to use. Every location decision comes back to one principle: gravity moves the water, so elevation matters.

Position the barrel directly under a downspout that drains the largest section of your roof for maximum collection. Place the barrel on a raised platform — two or three stacked cinder blocks or a purpose-built wooden stand — to increase water pressure at the spigot and provide clearance for a watering can underneath. A full 55-gallon barrel weighs about 460 pounds, so the platform must sit on level, compacted ground. Patio pavers or a concrete pad work well. Never set a full rain barrel on soft soil or a wooden deck that is not rated for the load.

Keep the barrel at least 2 feet from your foundation wall. Water that overflows or leaks near the foundation can cause basement seepage or erosion over time. Direct the overflow hose toward a garden bed, rain garden, or storm drain — never toward a neighbor’s property.

Modifying the Downspout

You have two main options for connecting the downspout to the barrel: cutting the downspout directly or using a diverter kit.

Direct cut method: Measure the height of the barrel’s inlet (including the raised platform). Mark the downspout at that height and cut with a hacksaw or tin snips. Attach a flexible downspout elbow to direct water into the barrel’s screened opening. This is the cheapest method but means all water enters the barrel — and all excess overflows — with no way to bypass the barrel in winter.

Diverter kit method: A downspout diverter ($15 to $30) installs in the middle of the downspout and routes water to the barrel through a connecting hose. When the barrel is full, the diverter automatically sends excess water down the original downspout path. In winter, you can disconnect the hose and water flows normally. The Oatey Mystic Rainwater Collection System ($20) and the Flexi-Fit Diverter ($25) are two reliable options. Installation requires cutting a small section of the downspout and snapping the diverter into place.

Setting Up the Overflow System

Every rain barrel needs an overflow outlet, and ignoring this step is the most common installation mistake. A 55-gallon barrel fills completely from just 0.1 inches of rain on a 1,000-square-foot roof section. Without overflow management, water pours over the top, floods the barrel base, and pools against your foundation.

Most barrels include an overflow port near the top. Attach a garden hose or flexible tubing to this port and route it at least 4 to 6 feet away from your foundation. Angle the hose downhill so water drains by gravity. For a cleaner setup, connect the overflow hose to a second rain barrel in series, effectively doubling your storage capacity. Link the two barrels with a short hose connected at the overflow port height. The first barrel fills completely before water transfers to the second.

Mosquito Prevention and Water Quality

Standing water breeds mosquitoes in as little as 7 days. A properly screened rain barrel prevents mosquito access, but you need to maintain that barrier.

• Ensure the mesh screen on the barrel inlet has no tears or gaps larger than 1/16 inch
• Keep the overflow hose connection sealed — mosquitoes can enter through loose fittings
• Add mosquito dunks ($8 for a 6-pack) to the barrel if you suspect any breaches. Each dunk treats 100 square feet of water surface for 30 days and is safe for plants and pets
• Use collected water regularly. A barrel that sits full for weeks becomes stagnant

Rainwater collected from asphalt shingle roofs is safe for watering ornamental plants, lawns, and most vegetable gardens. However, it is not potable. Avoid using rain barrel water on leafy greens that you eat raw unless you add a first-flush diverter that discards the initial dirty runoff from the roof. First-flush diverters ($20 to $40) capture the first 1 to 2 gallons of each rainfall event, which contains the highest concentration of bird droppings, pollen, and roofing granules.

Winterizing Your Rain Barrel

In regions where temperatures drop below 32 degrees F, you must drain and disconnect rain barrels before the first hard freeze. Ice expansion cracks plastic barrels, splits spigots, and breaks fittings.

1. Disconnect the downspout connection or diverter hose and reattach the original downspout extension
2. Open the spigot and drain the barrel completely
3. Remove the spigot and overflow fitting if possible, and store them indoors
4. Flip the empty barrel upside down or store it in a garage or shed
5. If the barrel is too heavy to move, leave it right-side up with the lid off so any rain or snow can drain freely through the open spigot

Reconnect in spring after the last hard frost date for your zone. Flush the barrel with a garden hose before the first use to clear any dust or debris that accumulated over winter.

Local Regulations and Rebates

Rainwater harvesting is legal in all 50 states, but some states and municipalities have restrictions on barrel size, number of barrels, or intended use. Colorado limited residential collection to two barrels (110 gallons total) until 2016 and still caps collection at 110 gallons per household. Most other states have no volume limits for residential use.

Many cities and counties offer rebates or subsidized rain barrels to reduce stormwater load on municipal systems. Programs in cities like Austin, Portland, Tucson, and Philadelphia have offered barrels at 50% to 75% off retail price. Check your city’s stormwater management or conservation department website before purchasing — you may get a $100 barrel for $25. Some utilities also offer free rain barrel workshops where you build your own barrel from a recycled food-grade drum.