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.
A rain barrel and a rainwater tank do the same basic job: they collect and store rain from a roof. The main difference is scale.
A rain barrel is usually a small, simple container connected to one downspout. It works well for watering a garden or filling watering cans.
A rainwater tank is usually larger and can collect water from more roof area. It is better when you want longer storage, more irrigation capacity, or a system that uses pumps, filters, or several outlets.
Neither option automatically makes roof runoff safe to drink. If drinking water is the goal, storage is only one part of a much larger collection, treatment, testing, and maintenance system.
Rain Barrel vs. Rainwater Tank at a Glance
| Feature | Rain Barrel | Rainwater Tank |
|---|---|---|
| Typical system size | Small | Medium to very large |
| Best for | Small gardens and occasional outdoor use | Larger gardens, irrigation, cabins, and larger reuse systems |
| Roof collection area | Usually one downspout | Can collect from one or more roof sections |
| Installation | Usually simple | Can require more planning |
| Water pressure | Low unless elevated or pumped | Depends on tank height and pump setup |
| Pump needed | Usually no | Sometimes |
| Overflow planning | Simple but still important | More important because larger flows may be involved |
| Foundation needs | Firm, level base | Often requires a carefully prepared base |
| Cleaning | Relatively easy | Can be more involved |
| Expansion | Limited | Usually easier |
| Indoor water use | Rare | Possible with suitable plumbing and treatment |
| Drinking-water use | Not automatically suitable | Not automatically suitable |
What Is a Rain Barrel?
A rain barrel is a small container placed near a downspout. Roof runoff enters the barrel through the downspout or through a diverter.
Most barrel systems include:
- an inlet
- a screened opening
- an overflow connection
- a spigot near the bottom
The screen helps keep leaves, insects, and larger debris out. The overflow carries excess water away when the barrel fills.
A barrel is often enough when the goal is simple garden watering.
You might connect a hose to the spigot, but pressure will usually be low. Gravity pressure depends on the height of the water above the outlet. Raising the barrel can improve flow somewhat, but any stand must safely support the full weight of the barrel.
Water is heavy. Even a relatively small container can weigh hundreds of pounds when full.
What Is a Rainwater Tank?
A rainwater tank is a larger storage container designed for collecting and holding more runoff.
The word "tank" covers many different systems. A tank might be installed beside a house, behind a shed, near a garden, or as part of a larger cistern system.
Depending on the intended use, a tank system may include:
- leaf screens
- gutter guards
- a first-flush device
- inlet screens
- calming inlets
- overflow piping
- tank vents
- pumps
- filters
- level controls
- irrigation connections
A first-flush device diverts some of the first runoff from a roof before water enters storage. This can reduce some of the dust, droppings, and loose debris washed from the collection surface. It does not make the remaining water automatically safe to drink.
Larger tanks also need more attention to their foundation, overflow route, connections, and access for cleaning.
Which One Holds More Water?
A rainwater tank normally holds much more water than a rain barrel.
That does not mean a larger tank is always the better choice.
Your useful storage capacity depends on three main things:
- How much roof area drains into the system.
- How much rain falls.
- How much water you actually use between storms.
Installing a very large tank on a small roof may leave much of the tank empty. A small barrel connected to a large roof may fill quickly and overflow during many storms.
The goal is to match storage to your collection area and water demand.
Estimating How Much Rain Your Roof Can Collect
In U.S. units, a useful theoretical estimate is:
Gallons collected = roof area in square feet × rainfall in inches × 0.623
For example, if 500 square feet of roof drains toward your storage and a storm produces 1 inch of rain:
500 × 1 × 0.623 = about 312 gallons
That is a theoretical roof yield before losses.
Real collection will be lower because water can be lost through first-flush diversion, splash, gutter overflow, leaks, evaporation, and other parts of the system.
A 50-gallon barrel would therefore fill quickly in this example. A larger tank could capture more of the storm.
Rain Barrels Are Better for Simple Systems
A barrel often makes sense when you mainly want water for a few garden beds, containers, or nearby landscaping.
It has several practical advantages.
Installation Is Usually Easier
A typical barrel can often be connected to one downspout without major plumbing.
You still need a stable base, screened openings, and a safe overflow route, but the system has relatively few parts.
Cleaning Is Easier
Small containers are usually easier to drain, inspect, and clean than large tanks.
That matters because sediment can slowly collect at the bottom.
It Works Without Electricity
A watering can can be filled directly from the spigot. A short hose may also work when there is enough height difference between the barrel and the watering point.
There is no need to add a pump unless your use requires more pressure or flow.
It Works Well for Small Water Demands
If you only need a modest amount of water between storms, storing hundreds or thousands of gallons may not be necessary.
Rainwater Tanks Are Better When Demand Is Higher
A tank becomes more useful when a barrel cannot store enough water for the intended job.
Larger Gardens
A large garden can use stored water much faster than a few containers or flower beds.
More storage can provide water for a longer period between rains.
Larger Roof Collection Areas
If several downspouts or a large roof can supply the system, a tank can capture runoff that would quickly exceed the capacity of one barrel.
Pumped Irrigation
Drip irrigation and other watering systems may need more pressure than a low barrel can provide.
A tank can be paired with a suitable pump when needed.
When choosing a pump, the important factors include the required flow, pressure, vertical lift, pipe size, power supply, and protection against running dry.
Cabin or Household Reuse
Larger non-potable systems may supply uses beyond garden watering where local rules allow it.
Non-potable means water that is not intended for drinking.
Indoor rainwater plumbing can require backflow protection, separation from drinking-water plumbing, treatment, labeling, permits, or professional installation depending on the location and intended use.
Check current local requirements before connecting collected rainwater to household plumbing.
Water Pressure Is Different From Storage Capacity
A larger tank does not automatically mean stronger water pressure.
Gravity pressure comes from head height, which is the vertical distance between the water surface and the outlet or point of use.
A tall, elevated container can sometimes provide more gravity pressure than a much larger tank sitting at ground level.
As the water level falls, gravity pressure also decreases.
This is why a large ground-level tank may still need a pump for sprinklers, long hose runs, or household distribution.
A barrel can work well without a pump when you are filling watering cans or using a short gravity-fed line.
Both Systems Need a Safe Overflow
Every rainwater container eventually fills.
Alongside choosing an appropriate rainwater tank size, assess a storage-tank design compatible with the location.
Once it does, the incoming roof runoff needs somewhere to go.
A rain barrel may only need a properly sized overflow hose or connection that sends water to a suitable drainage area.
A large tank can receive much more water, so overflow planning becomes especially important.
Overflow should not send water toward:
- the home's foundation
- crawl spaces
- neighboring property
- unstable slopes
- electrical equipment
- areas where standing water creates problems
Do not rely on the storage tank itself to control all stormwater during heavy rain. Once storage is full, the system must safely handle continuing roof runoff.
Tank and Barrel Foundations Matter
Stored water is extremely heavy.
One U.S. gallon of water weighs about 8.34 pounds. That means the water alone in a 1,000-gallon tank weighs roughly 8,340 pounds.
The container and hardware add more weight.
A small rain barrel still requires a solid, level surface. If you elevate it, use a support designed for the full load rather than loose blocks or an unstable improvised stand.
Large tanks need a foundation that follows the tank manufacturer's requirements and accounts for local soil and site conditions.
Poor support can cause a tank to lean, deform, settle unevenly, or damage its connections.
Large-system foundation work is one place where professional site advice may be appropriate.
Connections Become More Important With Larger Tanks
A basic rain barrel might have only an inlet, overflow, and spigot.
A larger tank often has several fittings.
One common fitting is a bulkhead fitting. It creates a sealed connection through the wall of a tank so pipe, valves, or other plumbing can be attached.
Before buying or installing components, check:
- fitting diameter
- thread type
- pipe or hose size
- location of the opening
- available clearance
- gasket placement
- whether the tank wall is suitable for the fitting
Do not assume two parts fit just because both are described with the same nominal pipe size.
Can You Connect Several Rain Barrels Instead?
Sometimes.
Multiple barrels can be linked to increase storage without installing one large tank.
This can work well when:
- water demand is moderate
- space is spread along a wall
- you already own suitable barrels
- you want a system that can be expanded in stages
However, a multi-barrel system creates more fittings, hoses, seals, and connections that can leak or clog.
The barrels also need to fill and drain in a controlled way.
Once a system begins using many barrels, a single properly sized tank can become simpler to manage.
Which Is Easier to Maintain?
A rain barrel usually wins for simplicity.
You can normally inspect the screen, outlet, overflow, and inside of the container without much equipment.
A tank may require more maintenance points, especially if the system includes filters and a pump.
Regardless of size, routine maintenance can include:
- removing leaves from gutters and screens
- checking inlet screens
- clearing overflow piping
- checking for mosquito access
- inspecting fittings for leaks
- removing accumulated sediment when necessary
- checking pumps and filters if installed
Keep access openings securely covered and screened as appropriate.
Never enter a tank or cistern. Tanks can present confined-space hazards even when they appear empty.
What About Freezing Weather?
Both barrels and tanks need climate planning.
Exposed pipes, valves, pumps, filters, and small containers are particularly vulnerable to freezing.
A barrel that is not intended for winter use is often drained and disconnected before freezing weather.
Large tank systems require a more complete freeze-protection plan because water may remain in storage while exposed plumbing freezes.
Do not assume insulation alone will prevent freezing.
The correct setup depends on local temperatures, tank location, pipe depth, equipment design, and whether the system needs to operate through winter.
Does Either System Make Rainwater Safe to Drink?
No.
Choosing a tank instead of a barrel does not turn roof runoff into potable water.
Potable means suitable for drinking.
Roof runoff can pick up contaminants from roofing materials, animals, dust, airborne material, gutters, storage surfaces, and plumbing.
If rainwater will be used for drinking, the entire system needs to be considered. That can include suitable collection surfaces, debris control, appropriate prefiltration, treatment designed for the hazards present, sanitary storage, ongoing maintenance, and current laboratory testing.
A simple screen, sediment filter, carbon filter, UV unit, meter, or test strip alone does not establish that collected rainwater is safe to drink.
Drinking-water systems should also follow applicable local health and plumbing requirements. Professional water-treatment guidance may be appropriate.
How to Choose Between a Rain Barrel and a Rainwater Tank
Start with the intended use rather than the container.
Choose a rain barrel when you want a simple system for small-scale outdoor watering and your storage needs are modest.
Choose a rainwater tank when you need more storage, want to collect from a larger roof area, expect to use a pump, or plan a larger irrigation or reuse system.
Then check the rest of the system.
Make sure you have:
- enough roof area to supply useful water
- suitable space for the container
- a firm and level base
- compatible inlet and outlet fittings
- a safe overflow route
- enough gravity head or an appropriate pump
- practical access for inspection and cleaning
- a plan for freezing weather if applicable
The best system is not necessarily the one that stores the most water. It is the one whose capacity, connections, water quality, and maintenance needs fit the way you plan to use it.
Frequently Asked Questions
Is a rain barrel the same as a rainwater tank?
They serve the same basic purpose, but the terms usually describe different scales. A rain barrel is generally a small container connected to a downspout. A rainwater tank usually holds more water and may be part of a larger collection, pumping, or irrigation system.
Is one rain barrel enough for a garden?
It can be enough for a small garden or occasional watering. The answer depends on your garden's water demand, barrel capacity, roof collection area, and how often rain falls. A large garden may empty one barrel quickly.
Can I connect multiple rain barrels together?
Yes, suitable barrels can be linked to increase storage. The system needs correctly sized and compatible connections, a controlled filling arrangement, and a safe overflow. More barrels also mean more fittings that require inspection.
Do I need a pump for a rainwater tank?
Not always. Gravity may be enough for filling watering cans or some low-pressure uses. A pump may be needed when water must travel uphill, through long pipe runs, or supply equipment that requires more flow or pressure.
Can I use a rain barrel with a garden hose?
Yes, but gravity-fed pressure can be low. Flow depends on the height of the water above the hose outlet, hose length, hose diameter, fittings, and restrictions in the line. Raising a barrel can increase head height, but the support must safely carry its full weight.
Is water from a rainwater tank safe to drink?
Not automatically. Roof runoff can contain biological, chemical, and physical contaminants. Drinking-water use requires a suitable whole-system approach that may include source control, prefiltration, treatment, sanitary storage, maintenance, current laboratory testing, and compliance with local requirements.
Should I buy a bigger tank than I think I need?
Not necessarily. Tank size should be based on roof area, rainfall, intended water use, available space, and expected losses. An oversized tank may rarely fill, while an undersized tank may overflow frequently. Matching storage capacity to your collection and demand is more useful than simply choosing the largest tank possible.
