The main types of water tanks
Material decides how long a tank lasts, how it fails and where it can go.
For most homes, a poly tank is the sensible default. Pick steel, concrete or fibreglass only when the site, the size or the look gives you a reason. The material changes how the tank ages and how it leaks.
The main materials side by side
| Type | Good for | Watch out for |
|---|---|---|
| Poly (plastic) | Most homes, easy delivery, light weight | Sun damage if the colour is wrong, stress at fittings |
| Galvanised or Colorbond steel | Corrugated rural look, larger volumes | Rust at seams and the base, liner wear |
| Concrete | Long life, underground or large tanks | Hairline cracks, weight, site works |
| Fibreglass | Strong and corrosion resistant | Fewer suppliers, more handling care |
| Bladder or flexible | Tight spaces such as under a deck | Needs a smooth, protected space |
Above ground or below ground
Above-ground tanks are easy to inspect and service. Underground tanks save space and keep water cool, but a fault is harder to find. If you are not sure you need to bury a tank, don't.
Slimline tanks suit narrow side access. They hold less and need a firm base, so check tank base preparation before you order.
Poly is not all the same
Good poly tanks are UV stabilised and opaque, which also slows algae. A thin or translucent tank grows algae faster and ages faster in the sun. Ask the supplier what the wall is rated for and what the warranty covers.
Match the type to the use
A tank for the garden can be almost anything. A tank that will feed toilets or laundry needs a proper inlet screen, a first flush diverter and a pump you can service. If you want to drink the water, read is tank water safe to drink before you spend anything.
For size, start from roof area and use, not from the gap beside the house. Sizing a rainwater tank walks through that order.
How to choose a tank type for your block
Match the tank to the site and the use, then look at price. This order avoids most regrets.
- Decide what the water is for. Garden use is forgiving. Toilets and laundry need a proper inlet screen, a first flush diverter and a pump you can service.
- Measure the space. A tight side access points to a slimline tank. A bigger yard gives you more choice.
- Think about the base. Every tank needs firm, even support. See tank base preparation before you order.
- Pick a material. Poly suits most homes. Choose steel, concrete or fibreglass only when the site or the look gives you a reason.
- Ask the supplier about the wall rating and warranty. A good poly tank is UV stabilised and opaque.
- Plan for upkeep. Above-ground tanks are easy to inspect. Buried ones hide faults.
What can go wrong with each tank type
Every material fails in its own way. Knowing the weak point tells you where to look during a check.
| Type | Typical weak point | What to look for |
|---|---|---|
| Poly | Fittings and sun damage | Cracks around fittings, chalky or faded walls |
| Galvanised or Colorbond steel | Seams and the base | Rust patches and weeping seams |
| Concrete | Hairline cracks and joints | Damp patches or seepage on the walls |
| Fibreglass | Impact and rough handling | Chips or cracks in the surface |
| Bladder or flexible | Rubbing and sharp edges | Folds, wear and a rough surface underneath |
| Underground (any) | Faults you cannot see | A level that drops with no use |
If you spot any of these, read water tank leaking: what to do.
Frequently asked questions
What is the best type of water tank for a home?
A UV-stabilised poly tank suits most homes. It is light, easy to deliver and needs little upkeep. Choose another material only if the site or size calls for it.
How long do different water tanks last?
Life depends on the material, the base and the water. Ask the supplier for the wall rating and warranty rather than trusting a general number.
Are underground water tanks better?
They save space and keep water cool, but faults are harder to find and the installation is bigger. Above ground is simpler for most sites.
Can I drink water from any type of tank?
No. The material does not make rainwater safe. Treat tank water as non-drinking unless it has been tested by an accredited laboratory.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- NHMRC. Australian Drinking Water Guidelines
- Australian Building Codes Board. National Construction Code — Volume Three (Plumbing Code of Australia)