Fibreglass vs concrete septic tanks: find the best for you

If you are looking to get an on-site septic system or one in your residence it is important to research the different types and understand the advantages and disadvantages of each to help you pick a tank that suits your needs. Two of the most common septic tanks are fibreglass and concrete. Both serve individual purposes and have their own advantages and disadvantages. Find out which type of septic tank would suit you best. Fibreglass septic tanks. 

Fibreglass septic tanks are made using fibre or sometimes modified plastic and often utilise a simple design. It usually is a rectangular or round-shaped fibreglass tank underground and is watertight. The tank includes an inlet and an outlet pipe. The inlet pipe works to collect the wastewater whilst the outlet pipe does the opposite and removes pre-processed wastewater and distributes it to watercourses and soil. Wastewater from plastic septic tanks is separated into three layers. The first or top layer has the oil and grease which floats above the water, this is often referred to as the scum. The waste particles and wastewater are in the middle layer. The last layer has heavier particles which form a layer of sludge.

Fibreglass Septic Tanks

Advantages of fibreglass septic tanks

There are a number of advantages to choosing a fibreglass septic tank. They are comparatively less heavy and can be easily installed anywhere. This is a major advantage for projects where it is difficult for cranes or trucks to reach. Given their lightweight they can be hauled in a pickup truck, making transport easy. Fibreglass septic tanks are also described to be sturdy and durable. This allows them to last for years without getting affected by sudden temperature changes or corrosion. It is easy to repair if the damage is caused compared to other types of tanks and tree roots find it difficult to penetrate into them, unlike concrete tanks.

Disadvantages of fibreglass septic tanks

There is a possibility of local corrosion in parts of a septic tank that aren't rust-resistant. This is likely as a fibreglass tank is not made of one part, meaning they have seams that are vulnerable to corrosion. This type of tank is handcrafted meaning the production is labour extensive which means it is more susceptible to human error. Fibreglass septic tanks are vulnerable to damage with soil shifts due to traffic or heavy vehicles going over the septic tank. They are also often more expensive than poly tanks Additionally, because the tank is lightweight it means it will float on top of the water, unlike a concrete septic tank. This problem can be resolved by anchoring the tanks.


Properly maintained fibreglass tanks can last more than 40 years and are unaffected by the gases from the sewage, allowing them to have a greater lifespan. They are also much easier to repair than concrete tanks, however, it is unlikely you will need to repair them.

Average cost

The cost of a fibreglass tank is determined by the size of the tank and the quality of the material used to make the tank. The average cost of a fibreglass tank in a home with three to four-bedroom is between $1, 500 to $2,000.

Concrete septic tanks

Concrete septic is a solid choice due to its material making it durable and is often preferred on construction sites. Investing in the right septic tank can make your life much easier as there will be fewer repair costs.

Advantages of concrete septic tanks

A major advantage of a concrete tank is its durability. Concrete is a sturdy material in comparison to plastic tanks or fibreglass septic tanks allowing it to be highly durable. This also means that it is highly unlikely that the tank will get incur any damage during installation. This type of tank is also rustproof, unlike a steel septic tank. A rustproof septic tank is important as it increases the durability of the tank consequently decreasing future costs. Another major advantage to concrete septic is that it won't float like a fibreglass or plastic tank. Nor will it collapse during pumping as the tank is sturdy. Concrete septic tanks are larger meaning they do not need to be pumped as often as other tanks, therefore increasing their effluent capacity and saving you money.

Disadvantages of concrete septic tanks

One of the disadvantages of concrete is that if the tank is damaged it is more difficult to repair in comparison to a plastic septic tank or fibreglass tank. This is because a concrete tank is one big piece as opposed to fibreglass tanks which are made of multiple pieces. If concrete tanks are not maintained properly they can crack, this is more applicable to older tanks. As concrete septic tanks are prone to cracking it means it is at risk of contamination because the wastewater can slip out. Additionally, concrete septic tanks are more difficult to install as they are heavier and less wieldy in comparison to fibreglass or plastic. This means installation requires heavy materials which increases cost.


The lifespan of a concrete septic tank depends on the acidity of the surrounding soil and the quality of the material used to construct the tank. However, in general, this type of tank has a greater lifespan of nearly 40 years.

Average cost

The cost of a concrete tank will depend on a number of factors including its size. Tanks range from 3,000 litres to 12,000 litres and prices range from $1,200 to $5,000.

Which type of septic tank is best? 

A concrete septic tank is highly recommended as it is easier to obtain a license and also because they come in many different sizes meaning it is easier to find the right one for you. However, there is no one answer to this question as your choice of tank depends on your need.

Septic tank maintenance tips

There are a number of actions you can take to help upkeep the health of your septic tank. This includes using specific cleaners suitable for septic systems and being aware that the family are taking antibiotics that can impact the bacteria in the system. You should also divert stormwater away from the disposal area as heavy rainfall can stop the system from working. Ensuring you do an annual check of the tank and check the depth of the soil and scum often. Do not use toilet disinfectants as they can destroy system bacteria and do not dump fats or grease down the kitchen as they solidify and create blockages.

Talk to a professional

If you are still unsure of what septic tank is right for you then that's okay because we can find a supplier who can help you out. Contact our expert team at 1300 691 912, or email our projects team with your requirements. They will find you a septic tank expert who can help you decide which septic tank is best for you.

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