Water conservation has become increasingly important across New Zealand. Whether you own a rural property, lifestyle block, commercial site, or urban home, investing in below ground water tanks is one of the smartest long-term solutions for reliable water storage.

Underground water tanks help homeowners collect rainwater efficiently while saving valuable outdoor space. They also protect stored water from sunlight, temperature fluctuations, and algae growth, making them an ideal option for New Zealand’s changing climate.

In this guide, we’ll explore everything you need to know about below ground water tanks in NZ, including benefits, installation, sizes, maintenance, and choosing the right tank for your property.

What Are Below Ground Water Tanks?

Below ground water tanks, also known as underground water tanks, are storage tanks installed beneath the surface of the ground. They collect and store rainwater or other water supplies while remaining completely hidden from view.

Unlike above-ground tanks, underground systems preserve your property’s appearance while offering excellent protection against weather conditions.

Benefits of Below Ground Water Tanks

Save Valuable Space

One of the biggest advantages is that underground tanks don’t occupy outdoor living space. This makes them ideal for:

Residential homes

Small urban sections

Commercial buildings

Schools

Public facilities

Better Water Quality

Since sunlight cannot enter underground tanks, algae growth is greatly reduced. The cooler underground environment also helps maintain better water quality throughout the year.

Improve Property Appearance

Many homeowners prefer underground tanks because they remain completely hidden. Your garden, driveway, or landscaping maintains a clean and modern appearance.

Long-Term Durability

Quality underground polyethylene or concrete tanks are designed to withstand New Zealand’s environmental conditions for decades with minimal maintenance.

Suitable for Rainwater Harvesting

Underground tanks work perfectly with roof rainwater collection systems, helping reduce reliance on mains water while lowering utility costs.

Common Uses of Underground Water Tanks in NZ

Below ground tanks are commonly used for:

water storage

Irrigation systems

Fire protection water supply

Commercial buildings

Schools and sports facilities

Emergency water reserves

Choosing the Right Tank Size

Selecting the correct tank depends on:

Small Homes

3,000L–5,000L

Suitable for:

Garden irrigation

Toilet flushing

Laundry

Medium Homes

10,000L–20,000L

Ideal for:

Family homes

Rainwater collection

Household water supply

Rural Properties

25,000L+

Best for:

Livestock

Irrigation

Whole-property water supply

Installation Process

Installing a below ground water tank involves several important steps.

Site Assessment

A professional installer evaluates:

Soil conditions

Groundwater level

Drainage

Access

Excavation

The installation area is excavated according to the tank dimensions.

Base Preparation

A stable sand or concrete base is prepared to ensure the tank sits level.

Tank Installation

The tank is carefully lowered into position using lifting equipment.

Plumbing Connections

Installers connect:

Inlet pipes

Overflow systems

Pumps

Filters

Household plumbing (if required)

Backfilling

Suitable material is placed around the tank while maintaining structural support.

Maintenance Tips

Proper maintenance helps maximise the lifespan of your underground tank.

Recommended Maintenance

Clean filters regularly

Inspect overflow systems

Check pumps annually

Remove sediment every few years

Inspect access covers for damage

Routine servicing helps maintain water quality and system efficiency.

Polyethylene vs Concrete Underground Tanks

Feature	Polyethylene	Concrete
Lightweight	✔	✖
Easy Installation	✔	✖
Corrosion Resistant	✔	✔
Long Lifespan	✔	✔
Heavy Vehicle Loading	Limited	Excellent
Cost	Lower	Higher

Both options perform well in New Zealand when installed correctly.

Why Choose Underground Water Tanks in New Zealand?

New Zealand experiences varying rainfall patterns across different regions. Underground rainwater tanks help homeowners prepare for dry periods while supporting sustainable water management.

Benefits include:

Reduced mains water usage

Lower water bills

Reliable emergency supply

Sustainable rainwater harvesting

Increased property value

Cleaner outdoor appearance

Conclusion

Below ground water tanks are an excellent investment for New Zealand homeowners, farmers, and businesses seeking a reliable, space-saving, and sustainable water storage solution. By harvesting rainwater efficiently and protecting it underground, these systems offer long-term savings while helping preserve one of New Zealand’s most valuable natural resources.

Whether you’re building a new home or upgrading an existing water storage system, choosing the right underground water tank can provide dependable water security for years to come.

Frequently Asked Questions

How long do below ground water tanks last?

High-quality underground tanks can last over 30 years with proper installation and maintenance.

Are underground tanks suitable for drinking water?

Yes. When installed with appropriate filtration and treatment systems, underground rainwater tanks can supply potable water.

Do underground tanks require maintenance?

Yes, but maintenance is generally minimal and includes checking filters, pumps, and cleaning sediment periodically.

Can I install a tank under a driveway?

Some underground tanks are specifically engineered for trafficable installations beneath driveways. Always select a tank rated for vehicle loads if required.

What size underground tank do I need?

The ideal size depends on your roof catchment area, household water usage, rainfall patterns, and intended use.