What Size Septic Tank Do I Need in Australia?

Grahams Precast Concrete Products • May 12, 2021

Why does size of a septic tank matter?

Good waste management is vitally important in every home, as well as at commercial sites. Part of this is making sure that wastewater is collected and drained effectively, and having the right septic tank installed is essential for this. Without the right septic tank in place, things can quickly become very unhygienic. You might be uncertain of the right size of septic tank for your property, so in this blog post, we look at what size septic tank you need for homes in Australia.

What is a septic tank?

A septic tank is a watertight container that’s buried underground and is used for collecting and storing wastewater from your home or business. It holds water for long enough to allow solids to separate from the water and then allows the water to drain out into a drain field.


Septic tanks can be constructed from fibreglass, plastic, or concrete. At Graham’s Precast Concrete Products, we specialise in high quality concrete septic tanks that are both safe and durable.

How do septic tanks work?

Septic tanks allow waste to separate into three layers: sludge, wastewater and scum as it is shown in this below diagram. The solids settle to the bottom, where microorganisms decompose them. The middle layer travels through the septic pipes and eventually leave the septic system and empty into the drainage field.

A Diagram Of A Septic Tank System Is Shown — Graham's Precast Concrete Products Pty Ltd in Kyogle, NSW

What influences the size of your septic tank?

Various factors will influence the size of the septic tank that your home or business needs.


  • The size of the property
  • The number of people who live or work there
  • How much wastewater your household generates
  • The type of system you require



The bigger or busier your property is, the larger the septic tank you’ll need.

What size septic tank do I need?

The answer will vary from person to person – every property is different and has different waste management demands. However, Standards Australia has issued guidelines on septic tank sizes. In line with this guidance, a house with between four and six bedrooms must have a tank that is at least 4,500L in capacity. This applies if you are producing “regular” quantities of wastewater. If your property produces more for any reason it’s possible that you’ll need a larger septic tank.


There isn’t a one size fits all approach when it comes to septic tanks, and problems are likely to arise if you get things wrong. To make sure you get the right sized tank to meet your needs and keep waste management running smoothly, it’s advisable to speak to professionals to work out what the right choice is for you.


If you have a commercial or residential property in New South Wales and are unsure about what size septic tank you need, the team at Graham’s Precast Concrete Products can help.


We have decades of experience with concrete products, septic tankswater troughs and feed troughs so give us a call today on 02 6632 2978. We have the knowledge and expertise to advise you on the most appropriate size of septic tank to meet your needs.


Our cost-effective and low-maintenance concrete septic tanks are long-lasting and dependable, with every one being carefully made by our team. Contact us now to discuss your requirements for a septic tank and decide on the right size for your property.

Would you like to learn more about Septic tanks?

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