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Do I need to add bacteria to my septic tank?

Septic tanks. We know, not an exactly 'exciting' topic to talk about but a necessary one nonetheless.

Ensuring your septic tank is working at 100% and at top efficiency is super important, so a common question we get asked is 'do I need to add bacteria to my septic tank?'. To help those of you out there who are asking the same question, or are now wondering if they should after reading the title, we have put together a little info to give you a hand. Give Express Wastewater a call on 1300 722 517 if you require some further assistance.

What is a septic tank?

A septic tank is used to treat sewage that is discharged from domestic homes.

How does a septic tank work?

The way a septic tank works is quite simple - some of the matter (ie. grease and fats) floats to the top of the tank and forms a scum layer, whilst the rest of the broken down solids (sludge) goes to the bottom of the tank.

Before it is used, a septic tank needs to be filled with water, which helps commence the treatment of sewage by the bacteria. The treatment that the waste undergoes by the bacteria changes the waste into effluent, otherwise known as wastewater, and a solid substance which is called sludge.

Septic System Experts | Septic Tanks | Express Wastewater
Diagram of a Septic Tank

Depending on the system, some septic tanks may treat either just blackwater (toilet discharge) or both grey and blackwater (all household wastewater).

Is your septic system working properly? Let our septic system experts help you.

Pros and cons of adding bacteria into your septic tank


  • Adding bacteria can be useful if you believe your septic tank is under unnecessary stress, or is being consistently overloaded by your household. This can include flushing things down the drain that shouldn't be flushed - e.g. tampons and chemicals - and/or being overloaded with usage. Additional bacteria in these scenarios help achieve more balance and stability in the tank.
  • The availability of pre-made products for your exact septic tank takes the guesswork out of figuring it out yourself, meaning less uncertainty regarding the result.


  • Much research has shown that they do not make a positive difference: A good deal of research that has been conducted has shown that adding bacteria to a septic system has no positive overall effect. Some of this research has even found that additives may be harmful to septic tank systems.
  • Additional bacteria do not replace proper and regular maintenance, and they should not be used this way. Nothing replaces proper maintenance regimes!
  • A lot of research suggests that adding bacteria does not make a considerable, positive difference overall. Some studies have even found that additional bacteria can be harmful in some circumstances.

What happens when there isn't enough bacteria in your septic tank?

Your tank will have a pungent, unpleasant odour as there are not enough bacteria to breakdown the waste properly.

So, do I need to add bacteria to my septic tank?

The best idea is to speak to an industry expert! It is always strongly suggested that you speak to a professional and they will be able to provide educated advice regarding your exact tank and its needs, as every tank is different.

Express Wastewater

Your experienced septic tank experts

If you would like to know more about installing a septic tank on your property, give Express Wastewater a call on 1300 722 517 and we would be happy to discuss your septic tank needs.


Australian Government - Department of Health (The septic tank):

Government of Western Australia - Department of Health (Understanding Septic Tank Systems):

Do I need to add bacteria to my septic tank? 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.