If you live in a rural area lacking access to a municipal sewerage system, you might want to look into the benefits of using concrete septic tanks to process and dispose of the wastewater from your home. The standard septic tank is a round, cylinder-shaped vessel with three different sections inside. The term ‘septic’ refers to the microorganisms within the vessel that hold and separate solids and liquids in the wastewater. Inside the vessel, the solids are broken down by the bacteria, and the liquid flows through a dividing wall into a second chamber where further settlement occurs until it flows onto an evapotranspiration field to evaporate.

Whether a concrete septic tank is intended for residential or commercial use will significantly influence the size of the vessel. Here we discuss how to determine the right size for domestic use.

In brief, the size of the septic tank your household requires will depend on

1. The expected volume of wastewater flow based on the size of your home
2. Local government regulations
3. The suitability of the ground geology

The underground soil type plays a key role in system effectiveness and, therefore, concrete septic tank size. Due to the vastly different soil and water features that can change by region, the tank size is tied to the requirements and recommendations of a designated department that oversees septic tank installations, often the Department of Health. To determine how suitable the ground on your property is for a septic tank system, a certified professional must visit the proposed installation area to perform certain tests. The results of the analysis and tests will decide if the desired location is acceptable and whether a specific septic tank system or size will be necessary.

To find the right size for your needs, you need to estimate the average volume of wastewater flow that the concrete septic tank has to handle. However, most recommendations for the smallest septic tank capacity in a domestic setting are 3550 litres as a starting point. A 3550-litre size tank is the bare minimum and can be suitable for a 2-bedroom, 3-bedroom house. Some installers even suggest adding an extra 1000 litres of septic tank capacity for homes with over 3 bedrooms.

See the following recommendations for details on minimum concrete septic tank capacity based on the number of residential bedrooms:

• 1-2 bedrooms – minimum septic tank capacity: 3500 litres
• 3 bedrooms – minimum septic tank capacity: 4000 litres
• 4 bedrooms – minimum septic tank capacity: 5000 litres
• 5 bedrooms – minimum septic tank capacity: 6000 litres
• 6 bedrooms – minimum septic tank capacity: 7000 litres

Before you ask yourself if it is wise to install a bigger tank right at the beginning, the answer is yes. Most companies recommend installing a larger concrete septic tank to accommodate home usage fluctuations, such as with parties or long-term guests. Instantly opting for a larger tank will also keep you from having to install a new one if your family size increases or you plan to make additions to your home, such as extra bedrooms, bathrooms, plumbing fixtures, etc.

In short, to determine the size of your concrete septic tank, you need to know the number of bedrooms in your home, the different water-using features installed, as well as the soil condition of your property. A licensed plumber will help you to communicate with the local government and take care of approvals prior to starting any septic tank installation job to ensure your wastewater system is efficient and compliant with local regulations, providing peace of mind for years to come.