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.
The best water tank to buy is the one that matches how you will use the water, where the tank will sit, and how much water you need to store.
For most home rainwater systems, a purpose-built polyethylene rainwater tank is the most practical choice. It is lightweight, does not rust, comes in many sizes, and is easier to install than concrete or steel. But an underground cistern, slimline tank, or even an IBC tote may make more sense in some situations.
The tank material is only part of the decision. You also need the right capacity, fittings, foundation, overflow setup, and protection from sunlight, freezing, and contamination.
What Type of Water Tank Is Best for Most Homes?
For above-ground rainwater storage, a rotationally molded polyethylene tank is usually the best all-around option.
Polyethylene is a durable plastic commonly used for water tanks. A good rainwater tank is made as one solid piece, which reduces the number of seams that could leak.
These tanks work well because they are:
- Resistant to rust
- Relatively lightweight when empty
- Available in many capacities
- Easy to connect to pumps and garden lines
- Available in shapes that fit different spaces
- Usually easier to install than concrete tanks
Look for a tank designed specifically for water storage rather than a general-purpose container.
If the water may ever be used for drinking, choose a tank specifically rated or certified for potable water. Potable means suitable for drinking-water applications. The tank alone does not make collected rainwater safe to drink.
Which Tank Is Best for Your Intended Use?
The best choice changes depending on what you want the water to do.
| Intended use | Tank type that often fits best |
|---|---|
| Garden watering | Polyethylene rainwater tank or rain barrel |
| Small garden system | Rain barrel or compact tank |
| Larger irrigation system | Vertical polyethylene tank |
| Narrow side yard | Slimline polyethylene tank |
| Cabin or off-grid storage | Purpose-built polyethylene or approved cistern |
| Very large storage system | Large polyethylene, concrete, fiberglass, or engineered cistern |
| Underground installation | Tank specifically designed for burial |
| Temporary non-potable storage | Suitable IBC tote |
| Drinking-water system | Potable-rated tank as one part of a complete treatment system |
Do not choose a tank simply because it holds the required number of gallons. Its intended installation matters just as much.
For example, an above-ground tank should not normally be buried. Soil pressure can crush a tank that was not designed to withstand it.
Polyethylene Water Tanks
Polyethylene tanks are a strong choice for many rainwater harvesting systems.
Advantages
They are relatively easy to transport and install while empty. They also resist corrosion, which is useful around water.
Many tanks already have molded locations for:
- Inlets
- Outlets
- Overflow fittings
- Inspection lids
They are available as round vertical tanks, squat tanks, slimline tanks, and other shapes.
Things to check
Make sure the tank is designed for your intended water use. You should also check whether the tank is intended for above-ground or underground installation.
Sunlight matters too. An opaque tank helps reduce the amount of light reaching stored water. Light can encourage algae growth.
Rain Barrels
A rain barrel can be a good choice when you only want a small amount of water for plants.
They are especially useful for:
- Patio gardens
- Raised beds
- Small yards
- Watering cans
- Simple gravity-fed hoses
Their main limitation is capacity.
A typical roof can collect more water during a storm than a small barrel can hold. Once the barrel fills, the remaining water must go somewhere safely.
Every rain barrel system therefore needs a suitable overflow route.
IBC Totes
An IBC tote can provide a large amount of storage in a compact footprint.
IBC stands for intermediate bulk container. These containers usually consist of a plastic inner tank supported by a metal cage.
They can work for some non-potable rainwater applications, but there are important limitations.
Only use a tote when you know its previous contents and know that the container is suitable for water storage. A used tote that previously held unknown chemicals should not be assumed safe just because it has been washed.
IBC totes also need protection from sunlight. The translucent plastic can allow algae growth when water receives enough light.
For a permanent home rainwater system, a tank designed specifically for rainwater storage is often easier to manage.
Slimline Water Tanks
Slimline tanks are designed for tight spaces.
They may fit:
- Along fences
- Beside garages
- Next to houses
- In narrow side yards
Their narrow shape is useful when a large round tank will not fit.
Check the manufacturer's installation requirements carefully. Some slim tanks need specific support or anchoring arrangements because their tall, narrow shape creates different forces than a broad round tank.
Underground Water Tanks
An underground cistern can be useful when you need substantial storage but do not want a large tank occupying yard space.
However, underground tanks are not simply above-ground tanks placed in a hole.
A buried tank must be designed for:
- Soil pressure
- Groundwater conditions
- Burial depth
- Surface loads
- Inlet and outlet access
- Pump access
- Inspection and maintenance
Excavation also introduces serious safety risks.
Large underground systems are generally better planned with guidance from the tank manufacturer and qualified local professionals.
Concrete Water Tanks
Concrete tanks are often used for large or permanent storage systems.
Their weight makes installation much more involved than installing a plastic tank. They normally require equipment and proper site preparation.
Concrete may make sense when:
- Very large capacity is needed
- The tank is part of a permanent structure
- Underground installation is planned
- Local construction practices favor concrete cisterns
Cracking, sealing, access, and water chemistry may also need consideration depending on the design.
For a simple backyard rainwater system, polyethylene is usually easier.
Steel Water Tanks
Steel tanks can provide very large storage capacities and may suit properties where appearance or durability makes steel attractive.
However, steel tanks still require careful attention to:
- Interior liners or coatings
- Corrosion protection
- Tank connections
- Foundation requirements
- Installation instructions
Not every metal tank is appropriate for every type of water.
Again, the intended use and manufacturer specifications matter more than material alone.
How Big Should Your Water Tank Be?
Tank size should be based on three things:
- How much rainwater your roof can collect
- How often it rains
- How quickly you use the stored water
Buying the largest tank that fits your yard is not always necessary.
Estimate how much rain you 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, 1 inch of rain falling on 1,000 square feet of roof represents about:
1,000 × 1 × 0.623 = 623 gallons
That is the theoretical amount falling on the roof.
Your actual collection will be lower because of losses from:
- Roof wetting
- Gutter overflow
- First-flush diversion
- Screens and filters
- Splashing
- Leaks
- Water remaining in pipes
A first-flush diverter sends some of the first roof runoff away from the tank. That early runoff may contain more dust, leaves, droppings, and other debris.
Match storage to your water use
A gardener using 20 gallons every few days has very different storage needs from a property running several irrigation zones.
Consider how long you want stored water to last between useful rainfall events.
A bigger tank can carry more water through dry periods, but it also requires more:
- Space
- Foundation support
- Plumbing
- Overflow capacity
- Cleaning access
Make Sure the Tank Fits the Site
Before buying a tank, measure more than the space where it will eventually stand.
Check:
- Tank diameter
- Tank height
- Gate width
- Path width
- Roof overhangs
- Fences
- Utility lines
- Tree branches
- Access for delivery equipment
A tank that technically fits its final location may still be impossible to move there.
Leave enough room around important fittings and inspection openings for future maintenance.
A Full Water Tank Is Extremely Heavy
Water weighs about 8.34 pounds per U.S. gallon.
That means 1,000 gallons of water alone weighs roughly:
For a suitable tank for rainwater collection, first assess overflow capacity and ventilation for long-term storage.
8,340 pounds
The tank adds additional weight.
A large water tank therefore needs a level, stable base constructed according to the tank manufacturer's requirements.
Do not place a large tank on a deck, raised platform, roof, or other structure unless that structure has been specifically designed for the load.
Check the Tank Connections Before Buying
Tank fittings can cause more trouble than the tank itself if they do not match your plumbing.
Check the locations and sizes of the:
- Inlet
- Outlet
- Overflow
- Drain
- Inspection opening
Also find out what type of threads or fittings are used.
A bulkhead fitting is a fitting that passes through the tank wall and creates a sealed connection for a pipe or valve.
Your pump, hose, irrigation system, and overflow plumbing may all need adapters if their connection sizes do not match the tank.
Planning this before buying the tank can simplify installation considerably.
Do Not Ignore the Overflow
Every rainwater tank can eventually fill.
Once it does, the incoming water needs a controlled path away from the tank and nearby structures.
The overflow system should be able to handle expected incoming flow and discharge water somewhere appropriate for the property.
Poor overflow planning can cause:
- Erosion
- Mud
- Water against foundations
- Tank-base damage
- Unwanted ponding
Screens may also be needed to prevent mosquitoes and debris from entering through tank openings.
Think About How Water Will Leave the Tank
You may be able to use gravity for simple watering if the outlet is high enough above the point of use.
However, gravity does not create much pressure from a low tank.
For irrigation, longer hoses, sprinklers, or household reuse, a pump may be required.
When choosing a pump later, important factors include:
- Required flow rate
- Required pressure
- Vertical lift
- Pipe length
- Pipe diameter
- Power supply
Flow rate is how much water moves over a given time, such as gallons per minute.
Head height describes how high a pump must lift water and helps determine the pressure the pump must overcome.
The tank and pump should be planned together when the water system will need significant pressure.
Consider Your Climate
Climate can affect which tank works best and how it should be installed.
Freezing climates
Water expands as it freezes. Pipes, valves, filters, and pumps are often more vulnerable than the main tank itself.
Do not assume a tank can remain completely full through freezing conditions unless the manufacturer specifically allows the installation.
Winterizing requirements depend on the tank, plumbing arrangement, and local temperatures.
Hot climates
Opaque tanks help limit sunlight entering the stored water.
Keeping a tank shaded may also reduce heating, but the installation still needs to meet the tank manufacturer's requirements.
What If You Want to Drink the Water?
A potable-rated tank is only one part of a drinking-water system.
Roof runoff can contain contaminants from:
- Bird and animal droppings
- Dust
- Roofing materials
- Smoke and airborne particles
- Gutters
- Decomposing leaves
- Insects
- Microorganisms
A complete system may require appropriate collection materials, debris screening, first-flush management, suitable storage, several treatment stages, maintenance, and laboratory testing.
A sediment filter, carbon filter, UV unit, reverse-osmosis system, test strip, or water-quality meter should not be treated as proof that untreated roof runoff is safe to drink.
Anyone planning drinking-water use should follow current public-health guidance and local requirements and use qualified water-treatment help where needed.
Features Worth Looking For
A good water tank does not need dozens of accessories. It does need practical features that fit your system.
Useful features may include:
- Opaque walls
- Secure inspection lid
- Screened inlet
- Suitable outlet connection
- Proper overflow connection
- Drain or cleaning access
- Clearly stated installation requirements
- Material suitable for the intended water use
If the tank will hold potable water, look for documented suitability for potable-water storage rather than relying on marketing terms such as "food grade" without further information.
Common Water Tank Buying Mistakes
Buying by capacity alone
A tank might hold enough water but still be too tall, too wide, or difficult to deliver.
Ignoring outlet size
A small outlet or incompatible fitting can restrict your plumbing options.
Forgetting the overflow
Rain does not stop when the tank becomes full.
Installing on an unsuitable base
Thousands of pounds of water require proper support.
Using an unknown secondhand container
Previous chemicals or other substances may make the container unsuitable for water storage.
Buying an above-ground tank for burial
Buried tanks need to withstand forces that ordinary tanks are not designed to handle.
Assuming stored rainwater is drinking water
Storage does not remove biological or chemical contamination.
So, Which Water Tank Should You Buy?
For a typical homeowner collecting rainwater for gardening, irrigation, washing equipment, or other non-potable uses, a purpose-built opaque polyethylene rainwater tank is usually the best place to start.
Choose the shape and capacity based on your available space, roof collection potential, and expected water use.
A rain barrel works well for small gardens. A slimline tank helps where space is tight. A properly selected IBC tote may work for some non-potable applications. Underground, concrete, fiberglass, or steel tanks become more useful as storage requirements and installation complexity increase.
Whatever style you choose, verify the foundation requirements, connection sizes, overflow design, access for cleaning, and suitability for the intended water use before you buy.
Frequently Asked Questions
What is the best material for a rainwater tank?
Polyethylene is often the most practical material for residential above-ground rainwater storage. It does not rust, is relatively lightweight when empty, and is available in many sizes. Concrete, fiberglass, and steel can also be appropriate for larger or specialized installations.
Is a black water tank better than a white tank?
Tank color matters mainly because light entering stored water can encourage algae growth. An opaque tank that blocks light is generally preferable to a translucent tank. Do not judge light-blocking ability from color alone; check the manufacturer's specifications.
How large a rainwater tank should I buy?
Choose capacity based on roof area, local rainfall patterns, available space, and how quickly you use water. In U.S. units, 1 inch of rain on 1,000 square feet of roof represents about 623 theoretical gallons before collection losses.
Can I use an IBC tote as a rainwater tank?
Yes, an appropriate IBC tote can be used for some non-potable rainwater systems. You should know what it previously contained and confirm that it is suitable for your intended use. It may also need protection from sunlight.
Can an above-ground water tank be buried?
Not unless the manufacturer specifically says the tank is designed for burial. Soil and groundwater can place substantial pressure on an underground tank and may collapse an unsuitable model.
Can I drink rainwater stored in a water tank?
A water tank by itself does not make rainwater safe to drink. Drinking-water use requires a suitable collection and storage system, appropriate treatment, regular maintenance, current laboratory testing, and compliance with applicable local requirements.
Does a rainwater tank need a pump?
Not always. Gravity can work for some low-pressure uses. A pump is usually needed when you want higher pressure, longer water lines, sprinklers, certain irrigation systems, or household reuse.
What should I check before ordering a water tank?
Check the tank dimensions, delivery access, capacity, installation type, base requirements, inlet and outlet sizes, overflow connection, cleaning access, and suitability for your intended water use.
