Water Tank Sizes

When it comes to selecting the right rainwater tank, one of the most important factors to consider is water tank size. The correct size will ensure you have enough stored water for your household, garden, farm or business without wasting space or budget on unnecessary capacity.

With a wide range of water tank sizes available, understanding what each size is best suited for will help you make a smarter, long-term investment. From compact tanks designed for small gardens to large-scale tanks built for rural and commercial use, choosing the right size can dramatically improve water efficiency and reliability.

This guide breaks down water tank sizes into clear categories and explains exactly what each size is best used for.Water Tank Sizes Explained: Choosing the Right Water Tank for Your Needs

Understanding Water Tank Sizes

Water tank sizes are measured in litres and range from a few hundred litres to tens of thousands of litres. Each size serves a different purpose depending on water usage, available space, rainfall levels and whether the tank will be used as a primary or secondary water source.

Water tanks are generally grouped into three main categories:

• Small water tanks
• Medium water tanks
• Large water tanks

Each category suits different property types and water demands.

Small Water Tank Sizes

Small water tanks are ideal for properties with limited space or low water usage requirements. These tanks are commonly used as supplementary water sources rather than full household supply.

Typical Small Water Tank Sizes

Small water tanks generally range from 200 litres up to around 5,000 litres.

What Small Water Tanks Are Best For

Small water tanks are well suited for:

• Watering gardens and lawns
• Supplying water to garden beds and pot plants
• Washing cars or outdoor equipment
• Collecting rainwater from sheds or garages
• Backup water supply for dry periods

These tanks are popular in urban areas, townhouses and properties where space is restricted. They are also commonly installed as starter tanks or secondary tanks connected to existing systems.

Small tanks are easy to install, cost-effective and provide an efficient way to reduce reliance on mains water for everyday outdoor tasks.

Medium Water Tank Sizes

Medium water tanks are the most popular choice for residential homes. They offer a balance between storage capacity and space efficiency, making them suitable for a wide range of household applications.

Typical Medium Water Tank Sizes

Medium water tanks typically range from 5,000 litres to around 9,000 litres.

What Medium Water Tanks Are Best For

Medium water tanks are ideal for:

• Regular garden irrigation
• Laundry and toilet use
• Pool top-ups
• Washing vehicles and outdoor areas
• Partial household water supply

These tanks are commonly used in suburban and semi-rural homes where homeowners want to significantly reduce mains water usage. Medium water tank sizes can support multiple water outlets and are often integrated into household plumbing systems.

They are a practical choice for families who want reliable rainwater storage without moving to a large rural-scale system.

Large Water Tank Sizes

Large water tanks are designed for high water demand and long-term storage. These tanks are commonly used in rural, agricultural and commercial settings, as well as homes that rely entirely on rainwater.

Typical Large Water Tank Sizes

Large water tanks usually range from 13,500 litres up to 50,000 litres or more.

What Large Water Tanks Are Best For

Large water tanks are ideal for:

• Full household water supply
• Rural and off-grid properties
• Farms and agricultural operations
• Livestock watering
• Fire-fighting reserves
• Commercial and industrial use

These tanks provide the capacity needed to store water through extended dry periods. For properties without access to mains water, large tanks are essential for maintaining daily operations and household comfort.

Large water tanks can also be linked together to create even greater storage capacity where required.

Water Tank Categories by Design

In addition to size, water tanks are also categorised by their design and installation type. Each design supports different space and usage requirements.

Round Water Tanks

Round water tanks are the most common and structurally efficient option. They are ideal for properties with enough open space and are available in all size categories, from small to very large.

Slimline Water Tanks

Slimline water tanks are designed for narrow spaces such as along fences or beside buildings. They are popular in urban areas where space is limited but water storage is still required.

Underground Water Tanks

Underground water tanks are installed below ground level, making them ideal where visual appearance or space is a priority. These tanks are often used in new builds or properties with strict planning requirements.

Choosing the Right Water Tank Size

Selecting the correct water tank size depends on several key factors:

Water Usage

Understanding how much water you use daily is essential. Households using rainwater for toilets, laundry and gardens will require larger tanks than properties using water only for garden irrigation.

Roof Catchment Area

The size of your roof directly affects how much rainwater you can collect. Larger roof areas can fill bigger tanks more efficiently.

Local Rainfall

Areas with lower or irregular rainfall benefit from larger tank sizes to store enough water between rain events.

Available Space

Space limitations may influence whether a round, slimline or underground tank is the best option for your property.

Future Needs

Planning for future water use is important. Expanding gardens, additional household members or new structures can increase water demand over time.

Small, Medium or Large: Which Is Right for You?

• Small water tanks are best for gardens, sheds and low-usage applications
• Medium water tanks suit most residential homes and everyday household use
• Large water tanks are essential for rural, off-grid or high-demand properties

Choosing the right size ensures you maximise water efficiency while avoiding unnecessary costs.

Final Thoughts on Water Tank Sizes

Understanding water tank sizes is the key to selecting a rainwater storage solution that works for your property both now and in the future. Whether you need a compact tank for garden use or a large-capacity tank for full household or rural supply, choosing the correct size will ensure consistent water availability and long-term reliability.

By carefully considering your water usage, space and local conditions, you can select a water tank size that delivers maximum benefit for years to come.