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Choosing the right water storage container starts with one question: What will the stored water be used for? A container that works well for garden watering may not be suitable for drinking water, household plumbing, or long-term storage.
For most rainwater systems, look for a container that is made for water storage, blocks sunlight, can be cleaned, has useful inlet and outlet locations, and can safely handle the weight of a full tank. If the water may be used for drinking, the container also needs to be specifically suitable for potable water. Potable means water intended for drinking or food preparation.
Start With the Water's Intended Use
The intended use affects almost every other choice.
Garden and Irrigation Water
For watering plants, washing tools, or other non-potable uses, you have more flexibility.
Common choices include:
- Rain barrels
- Above-ground polyethylene tanks
- IBC totes with a known safe history
- Larger cisterns
- Metal water tanks
Non-potable means the water is not intended for drinking.
Even for garden use, avoid containers that previously held pesticides, fuels, solvents, or other hazardous materials. Cleaning a container does not necessarily make an unknown or hazardous container suitable for water storage.
Household Non-Potable Water
Water used for toilets, laundry, or other household purposes usually needs a more carefully planned system.
The tank must work with the:
- Pump
- Plumbing
- Filtration
- Overflow
- Venting
- Controls
- Backup water arrangement, if used
Rainwater plumbing may also be subject to local plumbing and cross-connection rules. Check current requirements before connecting stored rainwater to a building.
Drinking Water
Be much more careful if the water may eventually be used for drinking.
Choose a container specifically identified as suitable for potable-water storage. Do not assume that any plastic tank, rain barrel, food drum, or IBC tote is suitable.
The CDC recommends safe drinking-water containers that can be closed tightly and that limit contact between stored water and hands, cups, or other objects. Containers that previously held toxic chemicals should not be used for drinking-water storage.
The tank is also only one part of drinking-water safety. Roof runoff can pick up dirt, animal waste, organic material, metals, and other contaminants before reaching storage. A drinking-water system may require suitable collection materials, debris removal, first-flush management, treatment, laboratory testing, and regular maintenance.
A filter or tank labeled for drinking-water use does not by itself make collected rainwater safe to drink.
Choose a Container Type That Fits the System
Different containers work better in different situations.
| Container type | Often useful for | Main things to check |
|---|---|---|
| Rain barrel | Small garden systems | Capacity, overflow, screened openings, hose connection |
| Vertical poly tank | Medium to large above-ground systems | Potable rating if needed, fittings, foundation, sunlight resistance |
| Slimline tank | Narrow spaces beside buildings | Stability, access, fitting locations, available capacity |
| IBC tote | Larger non-potable DIY storage | Previous contents, light exposure, fittings, structural condition |
| Metal tank | Large outdoor storage | Interior suitability, corrosion protection, foundation |
| Underground cistern | Large systems with limited surface space | Tank must be designed for burial, excavation, access, groundwater conditions |
Do not choose only by capacity. Two tanks with the same volume can have very different dimensions, outlet locations, cleaning access, and installation requirements.
Make Sure the Container Is Actually Designed to Hold Water
A large container is not automatically a water tank.
Purpose-built water tanks are designed to handle the outward force created by stored water. Containers designed for dry goods, light liquids, shipping, or other purposes may not be suitable.
This becomes more important as capacity increases.
Water weighs about 8.34 pounds per US gallon. That means the water alone weighs roughly:
- 55 gallons: 459 pounds
- 275 gallons: 2,294 pounds
- 500 gallons: 4,170 pounds
- 1,000 gallons: 8,340 pounds
The tank itself adds more weight.
A large tank therefore needs a stable base that can support the full load without settling, tilting, or creating dangerous structural loads. Be especially cautious before placing large tanks on decks, platforms, roofs, elevated stands, or floors that were not designed for them.
For large or elevated installations, structural advice may be appropriate.
Pick a Material Suitable for the Water
Polyethylene Tanks
Polyethylene is common for above-ground rainwater storage because it does not rust and can be molded into many sizes.
Check that the particular tank is designed for:
- Water storage
- Outdoor exposure, if installed outside
- Potable water, if drinking-water use is planned
- The temperature range at the installation site
Do not assume that the recycling symbol or plastic type alone proves that a tank is suitable for drinking-water storage.
IBC Totes
IBC totes can hold a useful amount of water in a relatively small footprint. Their built-in valve can also make plumbing easier.
The biggest issue is their history.
Use an IBC only when you can reliably determine what it previously contained and whether the container is appropriate for your intended use. Avoid totes with unknown histories.
Clear or translucent IBC bottles also admit a great deal of light. Sunlight can encourage biological growth in stored rainwater. An opaque, weather-resistant cover or enclosure may help block light, but it should not trap damaging heat or hide leaks and damage that need inspection.
An IBC tote should not automatically be considered suitable for drinking water just because it was previously used for a food product.
Metal Tanks
Metal tanks can provide large storage capacity and can last a long time when designed and maintained correctly.
Check:
- What material contacts the water
- Whether any coating is suitable for the intended water use
- Corrosion conditions
- Connections between different metals
- Access for inspection
Stored rainwater can vary in chemistry, so tank material and coatings matter more when the water is intended for household or drinking-water treatment systems.
Avoid Unknown Used Containers
A cheap used container can create an expensive problem.
Containers that previously held hazardous chemicals should not be reused for drinking-water storage. CDC guidance specifically warns against using containers previously used for toxic chemicals.
For any used container, try to confirm:
- Original contents
- Container material
- Intended use
- Age
- UV damage
- Cracks or deformation
- Condition of the outlet
- Condition of the supporting cage or frame
An uncertain history is a strong reason to choose another container.
This matters especially with used barrels and IBC totes sold through classifieds or industrial surplus sellers.
Choose the Right Capacity
Bigger is not always better.
Storage capacity should match both how much rainwater you can reasonably collect and how quickly you plan to use it.
Consider:
- Roof collection area
- Local rainfall patterns
- Intended water use
- Space available
- Dry periods
- Overflow location
- Cost and complexity of larger foundations and plumbing
A small garden may work well with one or two barrels. A household irrigation system may benefit from several hundred gallons. Larger property or household reuse systems may require thousands of gallons.
Do not size the tank from rainfall alone. A large tank provides little benefit if the roof cannot fill it often enough or if your water use is too small to cycle the stored water.
Likewise, a very small tank may overflow repeatedly during rainy weather and run empty soon afterward.
Check the Dimensions, Not Just the Gallons
Capacity numbers can hide installation problems.
Before buying a tank, check its actual:
- Diameter
- Width
- Length
- Height
- Empty weight
- Full operating weight
Then measure the route to the installation area.
A tank might fit beside the house but not fit through a gate. An IBC tote may fit through a driveway but leave no room to reach its valve. A tall tank may interfere with roof overhangs or gutters.
Also leave working room for:
- Plumbing
- Filters
- Valves
- Cleaning
- Inspection
- Pump access
A tank squeezed tightly into a space can become difficult to maintain.
Check the Inlet, Outlet, and Overflow Connections
The right tank should connect to the rest of the system without awkward modifications.
Inlet
The inlet receives water from the roof or another supply.
Factor in a suitable container to store water long-term to assess tank footprint, connections, and site constraints.
Make sure there is enough room for the planned pipe size, debris screening, and any prefiltration equipment.
A first flush device is sometimes installed before the tank to divert an initial portion of roof runoff that may contain concentrated debris and contaminants. It is only one part of rainwater quality management and does not make the remaining water potable.
Outlet
The outlet sends stored water to a hose, pump, irrigation system, or other equipment.
Check:
- Thread type
- Connection diameter
- Outlet position
- Valve compatibility
- Access after installation
Many DIY tanks use a bulkhead fitting. This is a fitting that passes through the tank wall and seals around the opening so a pipe, valve, or hose connection can be attached.
Do not drill a tank unless its design allows fittings to be installed in that location. Curved walls, thin areas, structural ribs, and inaccessible interior surfaces can make modifications difficult or unreliable.
Overflow
Every rainwater tank needs a safe way to handle water after it becomes full.
The overflow should carry excess water away without causing:
- Foundation problems
- Erosion
- Flooding
- Tank instability
- Water backing up into the collection system
The overflow should also be protected against unwanted animal and insect entry where appropriate.
Look for Good Cleaning Access
Stored rainwater carries some sediment into the tank even when leaf screens and other prefilters are used.
Over time, sediment and organic material can accumulate.
A tank should allow reasonable access for:
- Inspection
- Flushing
- Sediment management
- Cleaning
- Repairing fittings
Tiny openings can make maintenance difficult.
At the same time, wide open containers are not a good choice for protected water storage. A proper lid or access cover should close securely.
For drinking-water storage, minimizing opportunities for hands, tools, animals, and debris to contact the stored water is especially important. CDC guidance favors covered containers and dispensing arrangements that reduce direct contact with the water.
Block Sunlight
Sunlight is one of the main reasons a clear container can be troublesome for outdoor water storage.
An opaque tank helps reduce the amount of light reaching the stored water. That can make biological growth easier to manage.
Look for a tank designed for outdoor use rather than assuming that any dark-colored plastic container can remain outside indefinitely.
UV exposure can weaken some plastics over time.
If you use a translucent tank, consider how it will be shaded or covered while still allowing inspection, airflow around the tank, and access to fittings.
Plan for Venting
Water entering or leaving a closed tank displaces air.
A proper storage tank therefore needs a way to equalize air pressure without leaving a large unprotected opening.
Poor venting can contribute to:
- Slow filling
- Poor pump performance
- Tank deformation
- Pressure or vacuum problems
Vents should be sized and arranged for the system and protected where insects or debris could enter.
Think About Gravity and Pumping
The tank's outlet height matters.
A tank raised above the point of use can create some gravity pressure. However, simply raising a rain barrel a short distance does not create the pressure expected from typical household plumbing.
If irrigation equipment, sprinklers, filters, or fixtures need more pressure, a pump may be necessary.
Tank placement can also affect the pump's ability to receive water. Whenever possible, pumps should be selected and installed according to their required inlet conditions rather than assuming any pump can pull water from any tank arrangement.
Prepare a Proper Base
Most above-ground tanks need a smooth, stable, level base that supports the entire area specified by the tank manufacturer.
Possible base designs depend on tank size, tank shape, soil, climate, and manufacturer requirements.
Problems caused by a poor base can include:
- Tilting
- Uneven stress
- Cracking
- Fitting damage
- Pipe strain
Do not place a large tank on a few loose blocks unless the tank is specifically designed for that type of support.
The heavier the system becomes, the less forgiving an uneven foundation will be.
Account for Freezing Weather
Water expands when it freezes.
In freezing climates, the tank itself is only one part of the problem. Exposed valves, filters, pumps, hoses, pipes, and fittings may freeze before the main body of water does.
Check whether the container is intended to remain filled through freezing conditions.
Possible system designs include seasonal draining, protected plumbing, indoor storage, buried components, or other freeze-management methods. The correct approach depends on the equipment and climate.
Do not assume that wrapping a tank or pipe provides guaranteed freeze protection.
Do Not Bury an Above-Ground Tank
A tank designed to stand above ground may not be strong enough to resist soil pressure.
Underground tanks are engineered differently because they may have to withstand:
- Soil pressure
- Vehicle loads, where applicable
- Ground movement
- Groundwater pressure
- Empty-tank conditions
Use a tank specifically designed for burial when underground storage is required.
Excavation and underground tanks can also involve trench-collapse hazards, groundwater issues, utility lines, and confined-space hazards. Larger projects are good candidates for professional installation.
A Simple Way to Choose
For most homeowners, the selection process can be narrowed down to these questions:
- What will the water be used for? Decide whether it is garden water, household non-potable water, or potentially drinking water.
- How much storage makes sense? Match capacity to roof collection, rainfall, water use, and available space.
- Is the container made for water storage? Avoid improvised tanks that are not designed for the load.
- Is the material appropriate? Confirm outdoor and potable-water suitability where required.
- Do you know its history? Be especially cautious with used barrels and IBC totes.
- Will it physically fit? Check dimensions, access routes, working space, and full weight.
- Can it connect to the system? Look at inlet, outlet, overflow, vent, valves, and pump connections.
- Can you maintain it? You should be able to inspect, clean, drain, and service the tank.
- Can the site safely support it? Plan the foundation for the full weight of the container and water.
The best water storage container is not simply the largest tank that fits your space. It is the container that matches the water's intended use, safely handles the load, connects cleanly to the rest of the system, and can still be inspected and maintained years after installation.
Frequently Asked Questions
What is the best type of container for storing rainwater?
For many home rainwater systems, an opaque tank designed specifically for water storage is a practical choice. Rain barrels work well for smaller garden systems, while larger polyethylene or purpose-built metal tanks can serve higher water demands. The right choice depends on capacity, available space, connections, maintenance access, and intended water use.
Can I use an IBC tote for rainwater storage?
Yes, an IBC tote can be useful for non-potable rainwater storage if its previous contents are known to be appropriate and the container is in good condition. Avoid totes with unknown or hazardous previous contents. Because many IBC bottles admit sunlight, light control is also important.
Does a water tank need to be food grade?
For garden irrigation and many other non-potable uses, a potable-water container may not always be necessary. If the stored water may be used for drinking or food preparation, choose a container specifically suitable for that purpose. Do not rely only on the plastic type or appearance of the tank.
Is rainwater safe to drink if it is stored in a potable-water tank?
No. A potable-water tank only means the container is suitable for that intended use. Roof runoff can still contain microbial, chemical, and physical contaminants. Drinking-water use requires a suitable collection and treatment system, ongoing maintenance, current laboratory testing, and compliance with applicable local requirements.
Is a dark water tank better than a clear tank?
An opaque tank is usually easier to manage outdoors because it limits sunlight reaching the water. Clear and translucent containers can allow more light inside, which may encourage biological growth. Outdoor tanks should also be made to withstand the expected sunlight and weather exposure.
How big should my rainwater storage tank be?
Tank size should reflect roof collection area, rainfall patterns, intended water use, available space, and the length of dry periods. A larger tank is not automatically better. The goal is enough storage to be useful without creating unnecessary cost, weight, or maintenance.
Can I bury a regular plastic water tank?
Not unless the tank is specifically designed for underground installation. Above-ground tanks may collapse or deform under soil or groundwater pressure. Use a purpose-built underground cistern and follow its installation requirements.
How much does a full water tank weigh?
Water weighs about 8.34 pounds per US gallon. A 500-gallon tank therefore contains about 4,170 pounds of water, while a 1,000-gallon tank contains about 8,340 pounds. The tank itself adds additional weight, so the foundation or supporting structure must be designed for the full load.
