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What size septic tank do I need?

When it comes to wastewater in your home, you want to ensure that you have the best and most appropriate setup for your needs… otherwise things can get very messy (and smelly).

But how do you know what size septic tank you need? We know this can be a tricky question, which is why we have collated the information you need to help make a decision. If you need some extra assistance, give Express Wastewater a call on 1300 722 517 and we can discuss all your septic tank needs.

What is a septic tank?

A septic tank is a buried watertight container that can be constructed from concrete, fibreglass or polyethylene plastic. Its prime responsibility is to collect and store all the wastewater from the plumbing in your home before dispensing it through a drain field.

How does a septic tank work?

A septic tank stores wastewater, which aims at separating water from the oils, grease and organic material that are put down the drain in your home. The organic material will usually sit at the bottom of the tank and turn into sludge while the oils and grease, known as scum, will float to the top.

What factors affect septic tank size?

There are a few factors that affect the size of septic tank you will require, including:

  • The size of your home.
  • The size of your property.
  • The amount of people in your home.
  • The levels of wastewater you and your family produces.
  • What kind of system needed (e.g. all wastewater/greywater etc)
Looking to Install or Upgrade a Septic System? Let our septic system experts help you.

What size septic tank do I need?

What size septic tank you require is a tricky question to answer, as everyone is different. As a rough guide, in accordance with AS/NZS 1546.1:2008, a house with 4-6 bedrooms must have a tank that is a minimum of 4,500L in size if they produce ‘regular’ levels of wastewater. This draws a lot of assumptions though - it is best just to speak to your local wastewater specialists for assistance!

Here's an infographic summarising all the information listed above.

What Size Septic Tank Do I Need Infographic

Who do I speak to about septic tanks?

It is always recommended that you speak to an industry professional when it comes to septic tanks and your needs. Each household has different requirements, therefore it is important to review all factors before making a decision and professionals are qualified in the ares. Give Express Wastewater a call on 1300 722 517 and we can discuss your septic tank needs today!


Government of Western Australia (Understanding Septic Tank Systems):
Australian Government (The septic tank):
NSW Government (The easy septic guide):

What size septic tank do I need? Let our experts help you.

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Why Use Express Wastewater Solutions?


    Because we are not a manufacturer and not tied to one particular system we can always offer the best solution for your wastewater needs.


    Because we do this every day we have developed a close knit expert team for every step of the process – from plans and council paperwork to excavations, electrical and plumbing. We handle it all to make the whole process as stress free and quick as possible.


    Most people have never installed a home sewerage treatment plant and don’t know the next step, that is why we offer a free 30 minute phone consult with one of our experts to point you in the right direction.


    We handle your wastewater installation from start to finish we can deal with all the trades, council everything so you don’t have to worry about a thing.


    Have peace of mind knowing that Express are licensed, insured professionals that will do your job right the first time.


    Not sure what system is right for you, or want to know if your system is working properly? Just give one of our friendly wastewater experts a call and they will be more than happy to help.


    We will always look to repair your system rather than replace it if it does not need to be, which will generally save large amounts of money sometimes up to and over $10,000.