A rain barrel is one of the few garden projects that costs little to start and pays you back every time the sky opens. Your roof sheds more water than most people expect: about 623 gallons from a single inch of rain falling on 1,000 square feet, according to university extension services. A barrel catches a slice of that and holds it for the dry week that follows.
This guide is written for first-timers. It covers how much water you can realistically collect, the rules worth checking before you buy, seven ways to set up a barrel, a step-by-step install, and how to keep the whole thing safe, mosquito-free and unfrozen. It is written for US and UK gardeners, so if you call it a water butt, you are in the right place.
What You'll Learn
- How to work out how much water your roof can send to a barrel
- What to check on local rules, HOAs and placement before you buy
- Seven rain barrel setups, from a ready-made barrel to a disguised DIY drum
- How to install a barrel on a stable, raised base with a proper overflow
- How to control mosquitoes, avoid tip-overs and winterize
- What the water is good for, and what it is not
The Short Version
For most households, the right first step is one opaque, lidded 50 to 55 gallon barrel with a screen, a spigot near the base and an overflow hose, set on a level, raised base under a downspout. A diverter makes it a sealed system that fills from the side. The water is for the garden, not for drinking.
Check local rules first. Colorado, for example, caps households at two barrels and 110 gallons in total, and most other places leave it to local ordinances, homeowner associations and water companies.
How Much Water You Will Collect
Extension services share one formula. Multiply the roof area that drains to your downspout (in square feet) by the inches of rain, then by 0.623 gallons. The University of Arkansas Extension and Texas A&M AgriLife both publish it, and it gives the familiar answer of about 623 gallons for 1 inch of rain on 1,000 square feet. To find your own number, measure the length and width of the roof section that feeds the downspout.
The table below applies that formula to a few common roof sections. It is our own arithmetic, rounded to whole gallons, so treat it as a planning guide.
| Roof section draining to the barrel | ¼ inch of rain | ½ inch of rain | 1 inch of rain |
|---|---|---|---|
| 300 sq ft | 47 gallons | 93 gallons | 187 gallons |
| 500 sq ft | 78 gallons | 156 gallons | 312 gallons |
| 750 sq ft | 117 gallons | 234 gallons | 467 gallons |
| 1,000 sq ft | 156 gallons | 312 gallons | 623 gallons |
Two things stand out. First, a single barrel is rarely the limit on your roof; it is the limit on your storage. Frederick County, Maryland notes that 1/8 inch of rain on 750 square feet of roof will fill a 60-gallon barrel, and Clemson Extension says a roof section as small as 100 square feet can fill one quickly. That is why the overflow matters as much as the barrel itself.
Second, UK gardeners can skip the gallons. One millimetre of rain on one square metre of roof gives one litre, so 10 mm of rain on a 20 m² roof section sends about 200 litres to the downpipe. The RSPB says a standard water butt holds over 200 litres.
A roof section that sends more water than a barrel can hold is not a problem if the overflow is set up well. It is only a problem when the overflow dumps water against your foundation, which is the first thing to design out.
Before You Buy: Rules and Placement
Rules. There is no federal rule against collecting rainwater from your roof, but states and towns can set their own. Colorado is the best-known example: under HB 16-1005, a household may use up to two rain barrels with a combined 110 gallons, and, per Colorado State University Extension, the barrels count as a use of rooftop water, not a water right. Elsewhere, the usual advice is to start with a call to your municipality. Some towns restrict water harvesting, but many encourage it and some offer rebates or discounted barrels. If you live in a homeowner association, read its rules on visible barrels before you order. In the UK, councils and water companies often discount water butts, so check before you pay full price.
Placement. Pick a downspout that serves a decent roof section and sits close to where you water. Shade helps: the RHS says siting a water butt in shade keeps the water cooler and slows bacterial growth, and WebMD's rain barrel guide also suggests a shaded side of the house. The ground has to be firm and level, and you need room to run the overflow hose well away from the foundation.
7 Rain Barrel Ideas for Beginners
These are seven distinct setups, not seven versions of the same barrel. Start with the one that matches your skills, your downspout and your space.
A Ready-Made Flat-Back Barrel
The easiest start is a purpose-built barrel with a flat back that sits flush against the wall. Most come with a screened opening, a spigot or hose connection and an overflow outlet already built in, so you only have to deal with the downspout. A city installation guide notes that residential barrels commonly come in 50 to 90 gallon sizes, and most are around 50 to 60.
You shorten the downspout so it ends above the barrel's opening, or add a flexible extension that reaches it. Texas A&M AgriLife shows the flexible-extension method in its barrel guide, and it also lets you swap the downspout back in winter.
Trade-off: a ready-made barrel costs more than a DIY drum, and the plastic is not designed to freeze when full.
FCMP Outdoor Raincatcher 4000 Rain Barrel (50 gallon)
One suitable option for a first barrel. The listing describes a 50-gallon, flat-back polyethylene barrel, about 24 by 24 by 32 inches and 21 pounds empty, with a debris screen, a hose and shut-off valve, an overflow tube and a linking tube, plus side spigots for connecting a second barrel later. The maker states it is not suitable for freezing temperatures, so plan to drain it in fall. The listing offers several colours, so check the variant in your cart.
View on Amazon →
A DIY Drum Barrel
A food-grade 55-gallon plastic drum, a hose bib for the spigot, an overflow fitting and a piece of fiberglass window screen are the core parts. The University of Arkansas build uses a 3/4-inch outdoor hose bib, a 6-inch hole saw for the screened opening and a 2-inch pipe for the overflow. The University of Delaware's version adds a step that is easy to skip: caulk around the hose bibs inside and outside, and re-caulk them in spring.
Use a barrel that held something safe, and rinse it thoroughly if it contained any product. Texas A&M AgriLife publishes a build from a 44-gallon trash can, but Frederick County, Maryland steers people away from trash cans because they are hard to make child-safe and mosquito-proof. A lidded drum is the safer starting point. Plan an afternoon for the build (our estimate).
Trade-off: cheaper, but every drilled hole is a place that can leak if you rush the sealing.
A Sealed Barrel Fed by a Diverter
A diverter sits in the downspout and feeds the barrel through a flexible tube at the side. When the barrel is full, water carries on down the downspout as usual. The barrel stays closed, which keeps debris and mosquitoes out, and you keep your downspout in one piece. RainReserve and Good Ideas both sell kits for common downspout sizes, and the Good Ideas Flex Kit lists hole saws and a winter cover for the downspout hole. Those are manufacturer descriptions, not independent tests.
Measure your downspout before you order, because kits are sized for particular shapes, commonly 2 by 3 inch and 3 by 4 inch. We could not verify a trustworthy Amazon listing for these kits, so we have not linked one. Look for a kit that includes a way to connect to your barrel.
Trade-off: the diverter fills the barrel from one side, so you need a hole in the barrel at the right height, and a leaf-clogged diverter will need clearing.
Two Barrels, Daisy-Chained
Link two barrels near the base or via the overflow, so that when the first one fills it feeds the second. Frederick County suggests choosing a barrel that can be linked, and many ready-made models include a linking tube. Two 55-gallon barrels also match Colorado's limit of two barrels and 110 gallons, which makes this a useful template there.
Weight matters here. Using the 8.3 pounds per gallon that Rutgers NJ WaterSavers quotes, two full 55-gallon barrels weigh over 900 pounds, so both need a level, solid base.
Trade-off: twice the storage, but twice the weight and twice the footprint.
A Barrel at the Shed or Greenhouse
You do not need a house roof. A shed, garage or greenhouse roof is often the better source because the water is already close to where you use it. Clemson Extension says as little as 100 square feet of roof can fill a single barrel quickly, and a small roof also means a short gutter run. Put the barrel at a corner, and run the downspout straight into it.
If you grow under glass, this is a natural pairing. Our guide to backyard greenhouse ideas for year-round growing covers the structures, and a barrel at the corner keeps watering close to the plants.
Trade-off: a small roof fills the barrel quickly but empties it quickly too, so plan to use the water regularly.
A Raised Barrel on a Stand
Raising the barrel gives the spigot room for a watering can and adds pressure. Clemson Extension says barrels are typically raised 12 to 36 inches, and that each foot of height adds about 0.4 psi. By our arithmetic, a 3-foot stand gives roughly 1.2 psi, which is enough for a watering can, a gravity-fed hose or drip irrigation, as Clemson notes, but not for a spray nozzle.
Cinder blocks topped with pavers work, as do timber platforms and manufactured stands. Clemson also points out that a full 55-gallon barrel weighs over 450 pounds and elevated barrels must be properly secured to prevent injury. Never stack loose blocks, and never set a barrel on bare soil that can settle.
Trade-off: a higher barrel is more useful and more dangerous if it tips, so the base needs more care than the barrel does.
Good Ideas Rain Wizard Sturdy Stand (Oak)
A manufactured stand is one way to lift a barrel without building a base. This one is made for specific barrels: the maker's listing says it fits the Good Ideas 50-gallon Rain Wizard, Impressions Bali, Impressions Palm and Impressions series and supports over 600 pounds of water weight. It will not suit other brands, so check your barrel before ordering. If you buy a different barrel, such as the FCMP above, use cinder blocks and pavers or build a platform instead.
View on Amazon →
A Barrel Dressed for the Front of the House
If the barrel has to sit where people can see it, make it part of the planting. Frederick County notes that it is easy to screen a barrel with plants, and the Watershed Center suggests painting it. Keep the dark, opaque colour that Clemson recommends for blocking light and algae, and leave the lid, screen, spigot and overflow accessible. For painting plastic, follow the paint maker's directions for the surface.
A trellis with a climber, a planter at the base or a short screen of shrubs hides most of the barrel. Do not box it in so tightly that you cannot clean the screen or reach the spigot.
Trade-off: a handsome barrel is only handsome if you can still reach the parts that need maintenance.
How to Install a Rain Barrel
The steps are the same for most setups. The order matters, because the base comes first and the overflow comes before you ever fill the barrel.
What You Need
- A barrel with a lid or screen, a spigot and an overflow outlet
- A level base: pavers, cinder blocks, or a built stand
- A way to connect to the downspout: flexible extension, or a diverter kit
- An overflow hose long enough to carry water away from the foundation
- Fine mesh screen, if your barrel does not already include one
- A level, a hacksaw or tin snips, gloves, and a drill if you are cutting holes
- Pick the downspout. Choose one near where you water, with a decent roof section above it, and check any local or HOA rules.
- Build the base. Level the ground, then set pavers or blocks that can carry the load. Rutgers NJ WaterSavers puts a full 55-gallon barrel at about 460 pounds, and says the area must be level to prevent tipping.
- Set the barrel and check the spigot height. There should be room for your watering can, or a bucket, underneath it.
- Connect the downspout. Either cut the downspout above the barrel and add a flexible extension, or fit a diverter. Keep the piece you cut off, because many city guides tell you to put it back for winter.
- Fit the screen and overflow. The screen should be fine enough to stop mosquitoes. Run the overflow hose to a safe spot: one city guide says to direct it at least 6 feet from the foundation, ideally toward a garden bed or rain garden.
- Test it. Texas A&M and Coweta County Extension both suggest spraying water on the roof or into the gutter to check that the flow lines up with the barrel opening before the first real storm.
The diverter itself is quick. The Flex Kit's maker claims about five minutes of setup, which refers to the diverter and not the whole job. For a ready-made barrel on a prepared base, plan on an afternoon, and longer for a DIY drum (our estimate).
Cut downspouts leave sharp edges, so wear gloves. An empty plastic barrel can also blow away in strong wind, according to the University of Delaware, so strap or weigh it down until it has some water in it.
Mosquitoes, Kids and Weight
Mosquitoes. Standing water is a breeding site. Extension guidance converges on three habits: a tight lid or fine mesh screen, a clean screen, and a treatment for larvae. The University of Wisconsin says a fine mesh screen or filter on the lid keeps adult mosquitoes from laying eggs, and the Texas A&M, Kentucky and Coweta County guides all mention Bti, a bacterium that targets mosquito larvae. It is commonly sold as mosquito dunks.
Summit Mosquito Dunks (6-pack)
A Bti product for standing water. The maker says one dunk treats 100 square feet of surface water for 30 days, that it targets mosquito larvae only and that it is labelled for organic gardening by the EPA. Those are manufacturer claims, not independent testing. A barrel has a small surface, so follow the label for how much to use, and replace it on the schedule the label gives.
View on Amazon →Kids and animals. Keep the lid secure, and fix the barrel so it cannot be climbed or tipped. Colorado's law requires a sealable lid, and the rule is sensible everywhere. A barrel that fell over would release hundreds of pounds of water and weigh more than most adults.
Weight. Water weighs about 8.3 pounds per gallon, which puts a full 55-gallon barrel at about 460 pounds (Rutgers NJ WaterSavers). Our arithmetic for a 50-gallon barrel is roughly 415 pounds.
Rain that runs off a roof picks up bird droppings, leaves and other material. A Nebraska city's rain barrel brochure says plainly not to drink the water or use it on edible plants, and the Kentucky Energy and Environment Cabinet says rain barrel water is not for drinking.
What to Water With It
Barrel water suits lawns, flower beds, shrubs, trees and containers, and it is useful for rinsing tools or washing a car. Penn State's guide says to use it for lawns, plants, cars, tools and boots, but not for consumption. The City of La Vista, Nebraska says the water is naturally soft and free of minerals and chemicals, which plants like.
Edibles are where guidance differs. Penn State says it is best to use the water on inedible plants such as lawn, flowers, shrubs or trees, and La Vista advises against using it on edible garden plants. Clemson Extension publishes a separate factsheet, HGIC 1728, on applying harvested rainwater to edibles. If you plan to water vegetables, read your local extension's advice first, and consider our look at elevated metal raised beds for ideas where watering at the base of the plant is easy.
Use the water regularly. The Watershed Center's guide says to keep it moving so the barrel is empty for the next rain, which also means you get the most from every storm. For lawn watering amounts, our guide to how often to water your lawn will help you decide how much to apply.
Cleaning and Winterizing
A barrel is low maintenance, but not no maintenance. Clean the screen regularly so debris cannot block it. The Kentucky Energy and Environment Cabinet suggests cleaning the barrel itself once a year and using gutter guards to keep leaves out. In fall, keep your gutters clear of leaves, since organic matter in the gutter ends up in the barrel; the RHS says it can encourage bacterial growth in stored water.
Freezing is the main seasonal risk. Penn State says to drain and disconnect the barrel in winter because freezing and thawing can crack it. A city guide adds the details: empty it, remove it from under the downspout, reattach the cut-off piece of downspout, clean the barrel, and store it in a garage or shed or upside down outdoors. In the UK, Screwfix advises draining the water butt, disconnecting the diverter and leaving the tap open before hard frosts. Our guide on protecting your garden from the first frost fits alongside the fall routine.
| When | What to do |
|---|---|
| Spring | Check the barrel for cracks and leaks. Clear the screen, re-seal any fittings that need it, and reconnect the downspout or diverter. |
| Summer | Use the water often, keep the lid and screen in place and treat for mosquito larvae as the label directs. |
| Fall | Clear leaves from the gutters. Clean the screen, and consider gutter guards. Give the barrel its yearly clean. |
| Before the first hard freeze | Drain the barrel, disconnect it, put the downspout back to normal, and store the barrel upside down or under cover. |
Track Your Seasonal Jobs, Products and Equipment
A rain barrel only works if the spring check, the mosquito treatment and the fall drain-down actually happen. The Gardensted Lawn Care Planner is a 46-page printable PDF with seasonal checklists, a log of every product you use, equipment maintenance pages, a budget and shopping list and a year-end review. Its monthly pages and guides are written for lawns, so use the checklist and log pages to keep your barrel routine on the calendar next to your watering and mowing.
Get the Lawn Care Planner — $19.99Common Mistakes
- No overflow plan. The University of Wisconsin calls an overflow critical, and the Alliance for the Bay notes that an overflow smaller than the inlet can back water up and leak out of the barrel.
- Setting the barrel on soil. It can settle, and with 450 pounds of water that is a tip-over waiting to happen.
- Leaving the top open. A fine mesh screen or tight lid is the main defense against mosquitoes.
- Choosing a clear or light-coloured barrel. Clemson recommends a dark, opaque barrel to block sunlight and algae.
- Skipping the winter routine. Freezing and thawing can crack the barrel.
- Ignoring the rules. Colorado, homeowner associations and some towns have limits, so check first.
- Buying a stand that does not fit. Manufactured stands are matched to particular barrels.
- Treating the water as drinkable. It is not.
US and UK Differences
In the UK, a rain barrel is a water butt, and the usual setup is a butt with a tap, a lid and a diverter on a plastic downpipe. RHS-linked diverter kits are sized for standard 68 mm round or 65 mm square plastic downpipes and are not suitable for cast iron. The RSPB says a standard butt holds over 200 litres and fills quickly over winter, and suggests laying an old slab if the butt will stand on grass or soil. Water companies and councils often discount butts, and the diverter will cope with an overfull butt by passing water back to the downpipe, as Screwfix explains.
In the US, the local picture matters more. Rules vary by state, county and HOA, and climates differ: a barrel in a dry Colorado summer is used differently from one in a wet Mid-Atlantic spring. Follow your county extension office for freeze dates, the water's use on edibles and any local restrictions.
FAQ
How big should my first rain barrel be?
Most households start with 50 to 60 gallons. Roof area and rainfall decide how fast it fills, and a single barrel often fills quickly, so a second barrel is the easiest upgrade.
Is it legal to collect rainwater?
There is no federal rule against it in the US, but local and state rules vary. Colorado limits households to two barrels with a combined capacity of 110 gallons. Check your town and HOA.
Can I drink rain barrel water?
No. Roof runoff can carry bird droppings and other material. Extension and municipal guides are consistent that the water is for non-potable uses.
Can I use it on vegetables?
Guidance differs. Penn State says to stick to inedible plants, La Vista advises against using it on edible plants, and Clemson has a separate factsheet on applying harvested rainwater to edibles. Check your local extension.
How do I stop mosquitoes?
Keep a tight lid or fine mesh screen, clean the screen, and treat the water with Bti as the product label directs.
Do I need an overflow?
Yes. A full barrel has to send excess water somewhere safe, away from the foundation, and the overflow should not be smaller than the inlet.
How do I keep the water fresh?
The RHS suggests siting the water butt in shade and keeping gutters clear of debris. Use the water regularly so the barrel can refill.
Final Takeaway
Start with one barrel and do the boring parts properly: a level base, a screen, an overflow that leads away from the house, and a plan for winter. Choose the setup that fits your skills, a ready-made flat-back barrel for ease or a DIY drum for savings, and add a diverter or a second barrel later if you want more. Check your local rules, keep the water out of your kitchen, and use it often.
Product Summary
Every product below also appears in the article above. We have not tested any of them.
| Product | Best For | Why It Fits This Article | Key Feature to Look For | Amazon |
|---|---|---|---|---|
| FCMP Outdoor Raincatcher 4000 (50 gallon) | A first, ready-made barrel | Includes the screen, spigot hose, overflow and linking parts a beginner needs | Flat back, side spigots for linking; not for freezing temperatures | View on Amazon |
| Good Ideas Rain Wizard Sturdy Stand (Oak) | Raising a compatible Good Ideas barrel | Elevation adds pressure and room for a watering can | Fits specific Good Ideas 50-gallon barrels only | View on Amazon |
| Summit Mosquito Dunks (6-pack) | Treating standing water for mosquito larvae | Extension guides recommend Bti for rain barrels | Bti active ingredient; follow the label for dose | View on Amazon |
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