Whether you need to replace an existing septic tank or you are building a new rural home which requires one, choosing the right material is a big decision and there are a lot of factors to consider.
Septic tanks are made from concrete, plastic (polyethylene), fibreglass or steel, and there are pros and cons of each material - from the cost to the longevity and the ease of installation.
Before making a decision, you will need to consider your soil conditions, groundwater levels, budget and how long you plan to stay at the property.
Concrete septic tanks
Concrete septic tanks are made from precast concrete and have historically always been a popular choice.
Pros
- Built to last - with the right maintenance, concrete tanks can last 40 to 50 years. A good choice for your forever home
- Structural strength - if your concrete septic tank is underneath your driveway, it won’t be affected by cars driving over it every day
- Stays in place - when the groundwater level rises, lighter tanks can move, but a concrete tank will stay put
- Larger capacity - if you need a big septic tank eg if it serves multiple properties, concrete options have much bigger capacities than other materials
Cons
- More expensive - the tank itself is more costly and installation is a big added expense, with heavy lifting equipment and additional labour needed to install it correctly
- Delivery logistics - you can’t transport a concrete septic tank yourself, as they are too heavy. In some remote rural locations, access can be difficult for the large lorries needed to transport a concrete septic tank
- Can absorb moisture - the porous material can became a problem in acidic soils, leading to gradual deterioration. You can offset this with weatherproof coatings, which are another added cost
- Cracking - concrete is very durable, but cracks can happen over time, due to tree root intrusion or settling of the ground
Plastic tanks
Plastic septic tanks are seamless, one-piece tanks which won’t rust or corrode. They are a good option for many homes.
Pros
- Lightweight - they weigh a fraction of what a concrete tank weighs, meaning they are far easier to install
- Cost - a cheaper tank. Less equipment and less labour are needed to install a plastic septic tank, making it a more budget-friendly option
- Corrosion resistant - won’t be affected by acidic soil in the same way concrete tanks might be
- Easier to install in smaller spaces - if you can’t get a lorry and/ or crane onto your property due to narrow access, a plastic tank is much easier to install
Cons
- Floating risk - if you have a high water table, there is the chance your empty or partly empty septic tank could float during heavy rainfall
- Vulnerable to crushing - if you have a lot of vehicles or heavy machinery driving over the ground above your plastic septic tank, you risk tank failure through crushing
- Shorter lifespan - a well-maintained plastic tank can last as much as 30 to 40 years, which is about 10 years less than a concrete tank
- Smaller capacity - the biggest plastic tank can’t match the capacity of the biggest concrete tanks. If you need a big capacity, concrete is the best option
Fibreglass tanks
Fibreglass tanks are lightweight and easy to install, but with better durability than plastic tanks.
Pros
- Corrosion resistant - won’t rust or corrode, even when exposed to chemicals in the ground or in wastewater
- Less risk of floating - designed to resist floating, even in areas with high water tables
- Strength - fibreglass tanks are stronger than plastic
- Lightweight - much easier to handle and install than concrete tanks
Cons
- Cost - more expensive than plastic, but still cheaper than concrete
- Prone to cracking - may crack during installation if not handled correctly. Always work with experienced professionals
Steel septic tanks
Once popular, steel septic tanks are less widely used now due to both durability and cost.
Pros
- Stability - like concrete, steel is too heavy to float, even when the water table is high
- Structural integrity - resistant to forces in all directions when new and if properly maintained
Cons
- Corrosion - steel is prone to rust, which reduces the lifespan of a steel tank
- Cost - steel tanks are expensive
- Durability - less durable than other options means they are likely to need replacing sooner
- Difficult to remove - corroded steel tanks become hazardous and are difficult to remove safely
There are pros and cons of each of the materials. Ultimately, the best choice is the one which best meets your own specific requirements – including your budget, the type of soil on your property and how accessible your property is. Whether you choose concrete, plastic, fibreglass or steel, regular maintenance will help ensure the safety and longevity of your system.
If you’re ready to explore high quality septic tanks suited to a wide range of needs, take a look at the full range available at Tanks For Everything.
