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Diverting water from a downspout to a rain barrel is usually a simple job. The basic idea is to intercept some or all of the roof runoff, guide it into the barrel, and give excess water a safe path away when the barrel is full.
For most homes, there are two practical ways to do this:
- Install a downspout diverter that sends part of the flow through a hose into the barrel.
- Cut the downspout and direct it into the top of the barrel with an elbow or flexible extension.
A diverter is often the easier choice when you want the original downspout to keep working normally. A direct connection can move more water, but it requires a separate overflow system.
Before You Divert the Downspout
Start by deciding how you plan to use the collected water.
Rain barrel water is commonly used for non-potable purposes such as watering gardens and landscaping. Roof runoff can pick up dirt, bird droppings, roofing particles, chemicals, and other contaminants. Do not assume that water collected from a roof is safe to drink.
Also look at the entire path the water will follow:
- Rain falls on the roof.
- Gutters carry it to the downspout.
- The downspout or diverter sends it toward the barrel.
- The barrel stores the water.
- An overflow carries extra water away when the barrel is full.
The last step is easy to overlook. A typical rain barrel can fill quickly during a strong storm. Water still needs somewhere safe to go afterward.
Choose a Good Location for the Rain Barrel
Place the barrel close enough to the downspout that the connection does not require a long or awkward hose.
The ground should be firm and level.
A full barrel is very heavy. Water weighs about 8.3 pounds per U.S. gallon, so a 50-gallon barrel can hold more than 400 pounds of water before you count the container itself.
Use a stable base designed to support the loaded barrel. Do not place a large container on loose blocks, unstable soil, or a weak deck.
If you want to fill watering cans from a low-mounted spigot, raising the barrel slightly can also create useful clearance. Raising it does not create high water pressure, however. Gravity pressure from a short rain barrel is fairly low.
Method 1: Use a Downspout Diverter
A downspout diverter is often the cleanest way to connect a barrel while keeping the existing drainage system.
The diverter fits into the downspout. During rain, it redirects some water through a hose leading to the barrel.
Many diverter systems are designed so that when the barrel reaches a certain level, additional water continues down the original downspout instead of overflowing from the barrel.
1. Check the Downspout Size
Measure the downspout before choosing or installing a diverter.
Common downspouts are rectangular, but dimensions vary. The diverter needs to fit the actual downspout or use an appropriate adapter.
Do not rely only on what the downspout appears to measure from a distance.
2. Position the Barrel
Place the barrel in its final location before marking the downspout.
This matters because the height of the diverter relative to the barrel determines how the system fills.
With many diverter designs, the barrel's inlet or fill connection needs to be at a specified height relative to the diverter. Follow the instructions for the particular diverter design you are using.
3. Mark the Downspout
Hold the diverter or its installation template against the downspout and mark the required cut or hole.
Measure carefully before cutting.
Make sure there is enough room for:
- The diverter body
- The connecting hose
- Downspout brackets
- The barrel lid
- The barrel's inlet fitting
Avoid putting the hose where it will kink sharply.
4. Cut or Drill the Downspout
Use the type of cutting tool appropriate for the downspout material and the diverter design.
Wear eye protection and gloves because cut metal downspouts can have sharp edges.
Do not cut until you have checked the installation dimensions.
5. Install the Diverter
Fit the diverter into or through the downspout as required.
The connection should be secure enough that normal runoff does not leak excessively around it.
Make sure the remaining downspout is still properly supported. Cutting out a section can leave the lower part loose if the wall brackets are too far apart.
6. Connect the Hose to the Barrel
Run the diverter hose from the downspout to the barrel inlet.
Keep the hose:
- As short as practical
- Free of sharp bends
- Properly supported
- Sloped as required by the diverter design
A sagging hose can hold debris and standing water.
If the hose passes through the side of the barrel, use a fitting designed to create a watertight connection through the tank wall rather than pushing a loose hose through a rough hole.
7. Test the System
After installation, run water into the gutter or wait for a light rain and watch the entire system.
Check that:
- Water enters the barrel.
- Connections do not leak badly.
- The downspout remains secure.
- The hose does not back up.
- Excess water follows the intended drainage route.
If the diverter depends on the barrel water level to return flow to the downspout, test that function as well.
Method 2: Direct the Downspout Into the Barrel
The second option is to cut the downspout and place its outlet directly over or into the barrel inlet.
This arrangement is simple and can handle substantial flow, but it makes the barrel part of the main drainage path.
That means a dependable overflow connection is essential.
1. Place the Barrel Under the Downspout
Position the barrel where you want it permanently.
Mark the downspout slightly above the barrel inlet, leaving enough room for an elbow or flexible downspout extension.
Avoid placing the end of the downspout so deeply into the barrel that you cannot remove the lid or clean the inlet.
2. Cut the Downspout
Cut the downspout at the marked location.
Be careful not to damage nearby siding, brackets, wiring, or pipes.
Sharp metal edges should not be left exposed where someone can easily reach them.
3. Attach an Elbow or Extension
Connect an elbow or suitable downspout extension to direct water toward the barrel opening.
The outlet should deliver water onto the screened inlet without easily becoming disconnected during heavy rain.
Avoid long horizontal sections that can collect leaves and sediment.
4. Screen the Barrel Inlet
Do not leave a large open hole at the top of the barrel.
Use a secure screen or screened inlet that helps keep out:
- Leaves
- Larger debris
- Mosquitoes
- Animals
The screen still needs enough open area to accept the expected flow. A tiny screened opening can become overwhelmed or clogged during heavy rainfall.
Inspect and clean it regularly.
5. Install an Overflow
A direct-fed barrel needs a way to discharge water once it is full.
An overflow fitting is normally installed near the top of the barrel. A hose or pipe then carries excess water to an appropriate drainage location.
The overflow should generally be able to handle substantial incoming flow. A very small overflow line may not keep up with water arriving through a full-size downspout.
Route overflow away from foundations and other places where concentrated water could cause problems.
Look closely at building a homemade rain barrel diverter to understand cleaning access that supports sediment and odor management.
Do not simply let a full barrel spill against the house.
Diverter or Direct Downspout: Which Is Better?
The best arrangement depends on how you want the system to work.
| Setup | Main advantage | Main concern |
|---|---|---|
| Downspout diverter | Keeps the original downspout drainage path | Diverter and hose must be compatible and positioned correctly |
| Direct downspout connection | Simple path with good potential flow | Requires a properly sized and routed overflow |
A diverter is a good choice when you want the barrel to act as a side branch of the existing drainage system.
A direct connection makes sense when you want nearly all available downspout flow entering the barrel and you have a reliable overflow route.
Consider Adding Debris Control
Keeping leaves and roof debris out of the storage container reduces cleaning work later.
Your gutters are the first part of this system. Keep them reasonably clean.
Depending on the setup, you may also use:
- Gutter guards or leaf screens
- Downspout debris screens
- A screened barrel inlet
- A first-flush device
A first flush device redirects some of the initial roof runoff away from storage. The first runoff after a dry period may carry a larger amount of loose dirt and debris from the roof.
A first-flush device does not make rainwater safe to drink. It is simply one possible prefiltration step.
Make Sure the Barrel Can Vent
As water enters a closed barrel, air has to leave.
If the barrel is tightly sealed without adequate venting, incoming water can be restricted or create unwanted pressure.
A vent should be screened so mosquitoes and debris cannot easily enter through it.
Some barrel designs combine venting with a screened top inlet.
Do Not Forget Mosquito Protection
Standing water can become a mosquito breeding site if insects can reach it.
Keep openings securely screened, including:
- Main inlet
- Vents
- Overflow openings where appropriate
- Unused openings
Inspect screens for holes or gaps during routine maintenance.
A lid sitting loosely on top of an open barrel is not the same as a properly screened system.
How Much Water Can a Downspout Send to a Barrel?
Potential collection depends mostly on:
- Roof area draining to that downspout
- Amount of rainfall
- Gutter layout
- System losses
A rough theoretical estimate in U.S. units is:
Gallons = roof area in square feet × rainfall in inches × 0.623
For example, if 500 square feet of roof drains toward one downspout and the roof receives 1 inch of rain:
500 × 1 × 0.623 = about 312 gallons
Actual collection will be lower because some water is lost through wetting, splashing, overflow, first flush, gutter losses, and other factors.
This example also shows why overflow matters. A small rain barrel connected to a large section of roof may reach capacity well before a storm ends.
What If You Have More Than One Rain Barrel?
You can sometimes connect multiple barrels, but the plumbing arrangement matters.
A common approach is to connect barrels so water can move between them as the first barrel fills. The connecting fittings and hoses need enough capacity to transfer incoming water without causing the first barrel to overflow prematurely.
Another option is to divide incoming water between containers.
Do not assume that several barrels connected with a small garden hose will behave like one large tank during a heavy storm. Water may enter the first barrel faster than the connecting line can move it to the next one.
The final barrel or the overall system still needs a safe overflow route.
Common Problems to Avoid
Cutting the Downspout Before Positioning the Barrel
Small differences in barrel height can leave the diverter or elbow in the wrong position.
Place the barrel first, then measure.
Using an Overflow That Is Too Small
A barrel can receive a large amount of runoff quickly. A tiny overflow fitting may become the bottleneck.
Sending Overflow Toward the Foundation
The rain barrel should not turn a functioning downspout into a drainage problem.
Maintain a safe route for excess stormwater.
Leaving the Barrel Open
Open water encourages debris, insects, and animals to enter.
Use a secure lid and screened openings.
Using an Unsupported Barrel
Water is heavy. Make sure the barrel and any raised platform have a stable foundation.
Ignoring Freezing Weather
Water trapped in barrels, hoses, fittings, valves, and diverters can freeze.
In climates with hard freezes, follow an appropriate seasonal shutdown plan. This may include draining vulnerable parts and returning the downspout to its normal drainage configuration. The right method depends on the barrel, fittings, and local conditions.
A Simple Setup for Most Homes
For a basic garden-water system, a practical arrangement is:
Roof → gutter → downspout → diverter → screened rain barrel → overflow or normal downspout drainage
This keeps the original stormwater route available while allowing the barrel to collect useful water.
If you instead send the entire downspout directly into the barrel, treat the overflow as part of the main drainage system rather than as an optional accessory.
Once everything is connected, test the setup during rain. Watch where the water actually goes instead of assuming the system will behave as expected.
Frequently Asked Questions
Can I put a rain barrel directly under a downspout?
Yes. You can cut the downspout and use an elbow or extension to direct runoff into a screened barrel inlet. The barrel then needs a dependable overflow route for water that arrives after it is full.
Do I need to cut my downspout to install a rain barrel?
Often, yes, but not always. Many diverters require either cutting out a short section or drilling an opening into the downspout. The exact method depends on the diverter design.
What happens when a rain barrel connected to a downspout gets full?
Excess water must be redirected. Some diverters return it to the original downspout. Direct-fed barrels normally use an overflow hose or pipe that carries water to a safe drainage area.
Does a rain barrel need an overflow hose?
A directly connected barrel generally needs a dedicated overflow. Some downspout diverter systems handle excess water through the original downspout, which may reduce the need for a separate barrel overflow under normal operation.
Should the downspout go inside the rain barrel?
It can discharge through a screened top opening, but there is usually no need to extend the downspout deep into the barrel. Keep the inlet accessible for inspection and cleaning, and prevent mosquitoes and debris from entering.
How high should a rain barrel diverter be installed?
The correct height depends on the diverter design and the barrel's fill connection. Position the barrel first and follow the diverter's required relationship between its outlet and the barrel's maximum water level.
Can I use rain barrel water for drinking?
Do not assume roof-collected rainwater is potable, meaning safe for drinking. Drinking-water use requires consideration of the collection surface, contamination risks, prefiltration, suitable treatment, current laboratory testing, maintenance, and applicable local requirements. A rain barrel screen or simple filter alone does not establish that the water is safe to drink.
Can I connect two rain barrels to one downspout?
Yes, but the barrels and connecting plumbing need enough flow capacity to move water between them. The system also needs a final overflow path so excess rainfall can drain safely.
