As an affiliate, we may earn a commission from qualifying purchases. We get commissions for purchases made through links on this website from Amazon and other third parties.
You can make a homemade rain barrel diverter with basic downspout parts, a screened barrel inlet, and a clear path for extra water to keep flowing away from the house.
The simplest design sends the downspout toward the barrel during normal use and keeps the original lower downspout available as a bypass. A more advanced setup can return excess water to the downspout automatically when the barrel fills.
The important part is not just getting water into the barrel. Your diverter also needs to handle heavy rain, keep mosquitoes and debris out, and move overflow somewhere safe.
What a Rain Barrel Diverter Does
A rain barrel diverter takes some or all of the water flowing down a roof downspout and sends it into a rain barrel.
A good diverter should do three things:
- Send useful roof runoff into the barrel.
- Allow excess water to continue through the drainage system.
- Avoid creating a backup that could send water toward the foundation or gutter.
A rain barrel diverter is different from a first flush diverter. A first flush diverter discards the first portion of runoff from a storm because that water often carries more dust, bird droppings, and roof debris. A rain barrel diverter simply changes where the runoff goes.
CDC recommends considering first-flush diversion as one way to improve collected rainwater quality, but it does not make the water automatically safe to drink.
The Easiest Homemade Diverter Design
For a small garden rain barrel, the easiest dependable DIY design is a manual downspout bypass.
You cut the downspout above the barrel and attach a flexible downspout section or elbow. During the collection season, point it toward the screened barrel inlet. When the barrel is full, disconnected, or winterized, move the flexible section so it drains into the original lower downspout again.
This design is simple because it does not depend on a homemade internal valve or small hose to handle the entire roof flow.
The tradeoff is that it does not automatically switch itself when the barrel becomes full. You therefore need a separate barrel overflow unless you regularly move the diverter yourself.
What You Will Need
Exact parts depend on whether your downspout is rectangular or round, but a basic setup usually needs:
- A rain barrel with a secure lid
- A flexible downspout extension or suitable elbow
- A short replacement piece of downspout if needed
- A screened inlet
- An overflow fitting and pipe or hose
- Sheet-metal screws or appropriate downspout fasteners
- A measuring tape
- A marker
- A level
- Tin snips, a hacksaw, or another suitable downspout-cutting tool
- Gloves and eye protection
Use fittings made for the shape and size of your existing downspout when possible. Reducing a large downspout into a small pipe can create a bottleneck during heavy rain.
A regular garden hose is also usually a poor choice for carrying the full output of a roof downspout. It can work for controlled barrel overflow in some systems, but it should not be assumed to have enough capacity for all runoff from a large roof area.
How to Make a Simple Homemade Rain Barrel Diverter
1. Put the Barrel in Its Final Position
Set the barrel beside the downspout before cutting anything.
The base should be firm, flat, and able to support the barrel when it is completely full. Water is heavy. A 55-gallon barrel contains roughly 460 pounds of water when full, not counting the barrel and fittings.
Do not put a heavy barrel on loose blocks, unstable soil, or a platform that can tip.
Also leave enough room to reach the downspout, inlet, overflow, lid, and spigot for cleaning and maintenance.
2. Decide Where Water Will Enter
For the simplest arrangement, runoff enters through the top of the barrel.
Cut or use an inlet opening large enough to accept the downspout extension without restricting flow.
Cover the opening with durable insect-resistant screen.
CDC specifically recommends screening rainwater collection openings to help prevent mosquitoes from laying eggs in stored water.
Do not simply leave an open hole in the top of the barrel.
Leaves, insects, animals, and other debris can enter an uncovered barrel.
3. Mark the Downspout
Hold your flexible downspout section or elbow in position before making the cut.
You want enough room for the extension to reach the barrel without sharp bends or a long nearly horizontal run.
At the same time, preserve the lower section of the original downspout. That gives you a path for bypassing the barrel.
Mark the cut location only after the barrel and base are in their final positions.
4. Cut the Downspout
Wear gloves and eye protection.
Cut the downspout cleanly at your mark. Metal downspouts can have sharp edges after cutting, so remove or flatten dangerous burrs.
Do not work from an unstable ladder. If the required cut is high enough that you cannot reach it safely from the ground, roof or ladder work may be better left to someone with suitable equipment.
5. Attach the Flexible Diverter Section
Fit the flexible downspout piece or elbow onto the upper downspout.
Secure it well enough that wind and flowing water cannot pull it loose.
In the collection position, point the outlet into the screened barrel opening.
In the bypass position, it should be possible to redirect the same piece into the lower downspout or another suitable drainage path.
Avoid relying on tape alone for a permanent outdoor connection.
6. Add a Separate Overflow
Even with a movable diverter, an overflow is a good safeguard.
Put the overflow near the top of the barrel. A bulkhead fitting is useful here. A bulkhead fitting passes through the barrel wall and seals around the opening, giving you a secure connection for pipe or hose.
The overflow line should carry water away from the foundation to a place where runoff can safely drain.
Keep the overflow reasonably large and avoid unnecessary restrictions.
A barrel can fill surprisingly quickly during a strong storm. EPA guidance for rain barrels also emphasizes providing a proper overflow route rather than allowing a full barrel to spill uncontrolled beside the building.
7. Test the System With Water
Do not wait for a major storm to discover a problem.
Run water into the gutter or upper downspout at a modest rate and watch the complete path.
Check that:
- Water enters the barrel without splashing against the house.
- The inlet screen does not immediately clog.
- Downspout joints stay connected.
- The barrel does not leak around fittings.
- Overflow drains away from the foundation.
- The lower downspout remains usable when the barrel is bypassed.
Then try a somewhat stronger flow.
A homemade system that works with a trickle may still overflow at the connections during heavy rain.
Can You Make an Automatic Homemade Diverter?
You can, but it is more difficult to make one that works reliably.
Commercial-style automatic diverters commonly use a collector inside the downspout. Some runoff enters a side hose leading to a sealed inlet near the top of the barrel. When the barrel becomes full, water backs up in that hose, and additional runoff continues down the original downspout.
Penn State Extension describes this general arrangement: a diverter is installed in the downspout, a hose connects it to an inlet near the top of the barrel, and the system allows water to continue through the downspout once the barrel is full.
Evaluating building a DIY rainwater diverter helps assess installation planning for dependable ongoing service.
A homemade version needs several things to work together:
- A collector inside the downspout
- A watertight side outlet
- A hose that does not sag enough to trap debris
- A sealed barrel inlet
- Correct relative height between the diverter and barrel inlet
- An unrestricted path down the original downspout
The height relationship matters because the system uses backed-up water to stop additional flow toward the barrel.
A poorly placed homemade collector may capture almost no water during light rain, restrict the downspout during heavy rain, or clog with leaves.
For that reason, a simple open-top diverter plus a separate overflow is generally easier to build from ordinary materials.
Do Not Block the Main Downspout
One of the most important rules is to preserve adequate drainage capacity.
Do not install a homemade plug, small valve, or solid plate that completely blocks the downspout in order to force water toward the barrel.
If the barrel fills or the branch becomes clogged, water needs somewhere to go.
A blocked downspout can cause gutters to overflow. Depending on the building, that water may end up near siding, windows, the foundation, or other places where you do not want it.
The safer arrangement is always:
roof → downspout → diverter → barrel when available, with a clear bypass or overflow path for excess water.
Screen the Water Before It Enters
Your diverter will work better if large debris never reaches it.
Keep gutters reasonably clean. If appropriate for your system, use gutter guards, downspout screens, leaf strainers, or another form of coarse prefiltration.
Prefiltration means removing larger debris before water enters storage.
It does not make rainwater safe to drink. It mainly reduces leaves, twigs, insects, and sediment that could clog the system or collect in the barrel.
Check screens frequently during seasons when trees are dropping leaves, flowers, seeds, or needles.
A screen that is completely covered with debris can become a flow restriction during a storm.
Keep the Barrel Closed to Mosquitoes
Every opening into the barrel should either be closed or screened.
Check:
- The main inlet
- Overflow connections
- Vent openings
- Gaps around the lid
- Unused holes
Screens eventually tear, loosen, or become clogged, so inspect them as part of routine maintenance.
Consider Adding a First Flush Diverter
A rain barrel diverter and a first flush diverter can be used in the same system.
A first flush device sends the first runoff from the roof away from storage. This can reduce some of the concentrated dirt and contamination washed off the roof at the beginning of a storm.
It is most useful when water quality matters or when the roof sits through long dry periods between rains.
It is not a substitute for keeping the roof, gutters, screens, and barrel maintained.
It also does not turn roof runoff into drinking water.
Keep Rain Barrel Water Separate From Drinking-Water Plumbing
For ordinary DIY systems, rain barrel water is best treated as non-potable water.
Non-potable means water that is not intended for drinking.
Roof runoff can pick up bacteria, animal waste, dirt, and chemicals from roofing, gutters, piping, and storage materials. EPA notes that roof runoff may contain bacteria and chemicals collected from roof surfaces.
CDC likewise states that collected rainwater is not necessarily safe to drink and recommends regular testing for germs and chemicals when rainwater is used for drinking, cooking, or bathing.
Do not connect a homemade rain barrel directly to household drinking-water plumbing.
Using collected rainwater as drinking water requires a whole-system approach. That can include suitable collection surfaces, prefiltration, treatment designed for the actual contaminants, current laboratory testing, maintenance, protection against cross-connections, and compliance with local requirements.
A homemade downspout diverter alone does not address those issues.
How to Maintain the Diverter
Check the system periodically and after unusually heavy storms.
Look for:
- Leaves trapped in the diverter
- Sludge around the barrel inlet
- Loose downspout screws
- Cracked flexible pipe
- Leaking bulkhead fittings
- Torn insect screens
- Kinked overflow lines
- Overflow erosion near the house
- Standing water where mosquitoes could breed
Clean the barrel as needed rather than allowing sediment and organic material to build up indefinitely.
If you live where temperatures drop below freezing, disconnect and drain parts that could hold water. Penn State Extension recommends emptying and disconnecting rain barrels before winter where freezing can damage the system.
Your exact winter setup depends on climate, barrel material, pipe layout, and whether the original downspout must remain connected to another drain.
When a Homemade Diverter Is Not the Best Choice
A basic DIY diverter works well for many small rain barrels used for landscape watering.
A more engineered solution may make sense when:
- The downspout handles a large roof area.
- The building regularly receives intense rainfall.
- Downspouts connect to buried drains.
- You want automatic filling and automatic bypass.
- Several barrels or tanks are connected.
- Water will supply indoor fixtures.
- The system includes pumps or pressurized plumbing.
- Overflow cannot be safely discharged near the barrel.
- Local rainwater rules require specific components.
In those situations, downspout capacity, overflow sizing, backflow protection, and local plumbing requirements can matter more than the convenience of making a diverter from spare parts.
Frequently Asked Questions
Can I make a rain barrel diverter from a flexible downspout extension?
Yes. A flexible downspout extension can make a simple manual diverter. Point it toward the barrel when collecting water and reconnect or redirect it to the normal downspout when bypassing the barrel. The barrel should still have a safe overflow route.
Can I use a garden hose from the downspout to the rain barrel?
A garden hose may be too restrictive to carry the full runoff from a roof. Small tubing is better suited to systems designed to collect only part of the downspout flow. Do not reduce the entire downspout into a small hose unless the system has another unrestricted path for excess water.
Does my rain barrel need an overflow if I use a diverter?
Usually, yes for a simple homemade open-top system. A separate overflow provides protection if the barrel fills before you switch the diverter. Some properly designed automatic downspout diverters use the original downspout itself as the overflow path.
Where should the rain barrel overflow go?
Send overflow to a location where it can drain safely away from the building. Avoid dumping large amounts of water directly beside the foundation. The best location depends on grading, soil, drainage, neighboring property, and local stormwater rules.
Is a rain barrel diverter the same as a first flush diverter?
No. A rain barrel diverter sends runoff toward storage. A first flush diverter discards the first runoff from a storm before later water enters storage.
Should I screen the diverter or the rain barrel?
At minimum, prevent insects and larger debris from entering the barrel. Screens or other prefilters upstream can also reduce clogging. Any screen needs regular cleaning because trapped leaves can restrict flow.
Can I drink water collected with a homemade diverter?
Do not assume it is safe to drink. Roof runoff can contain germs and chemicals even when the water looks clear. Drinking-water use requires suitable collection, appropriate treatment, laboratory testing, ongoing maintenance, and compliance with applicable local requirements.
