No, not every house has a septic tank. Homes connected to a mains sewer network send wastewater to a central treatment system, while properties without access to mains sewerage may use a septic system or another type of onsite wastewater treatment system. Knowing which system your property uses is important for maintenance, renovations, plumbing problems, and buying or selling a home.
Key Takeaways
- Not every house has a septic tank.
- Urban homes are commonly connected to mains sewerage.
- Rural properties are more likely to use onsite wastewater systems.
- Property records can help identify your wastewater system.
- Septic systems require different maintenance from mains sewer connections.
Does Every House Have a Septic Tank?
No, most Australian homes connect to the reticulated mains sewer network rather than relying on a septic tank. In metropolitan Melbourne, the vast majority of residential properties have a sewer connection provided by the relevant water authority, and all wastewater leaves the property through that connection for treatment at a centralised facility.
Septic systems are used on properties that are not connected to the sewer network. This includes rural properties, properties in semi-rural areas where sewer infrastructure has not been extended, and specific regions like the Mornington Peninsula where reticulated sewer coverage remains incomplete across a large number of residential properties.
The simplest summary is that your property uses a septic system if it does not connect to the mains sewer. The two systems do not overlap. Every residential property must manage its wastewater through one or the other.
What Is a Septic Tank?
A septic tank is a below-ground wastewater treatment system that receives all household wastewater, separates solids from liquids, and begins the biological treatment process before effluent moves to the absorption field.
A complete explanation of what a septic tank is and how it functions covers the tank construction, how the two-chamber system works, the role of bacteria in breaking down waste, and why so many Mornington Peninsula properties rely on them.
In brief, wastewater from toilets, sinks, showers, and laundry enters the tank. Solids settle at the bottom as sludge. Lighter material rises as scum. The clarified liquid in between flows out to an absorption field where soil completes the treatment. The property owner is responsible for maintaining the whole system, including regular pump-outs and inspections.
Which Properties Are More Likely to Have a Septic System?
Properties more likely to have a septic tank installed are those in rural and semi-rural Victoria, coastal areas developed before sewer infrastructure arrived, large acreage blocks outside metropolitan Melbourne, and high-density septic areas like the Mornington Peninsula.
Properties more likely to use a septic system include:
- Properties in rural Victoria, where sewer infrastructure does not exist, and onsite treatment is the only option.
- Properties on large acreage blocks outside metropolitan Melbourne, where the distance from existing sewer mains makes a connection impractical or not yet available.
- Older properties in semi-rural areas built before sewer was extended to the suburb or street.
- Holiday homes and coastal properties that were built decades ago when the area was seasonal rather than permanently occupied.
- Properties across the Mornington Peninsula, where around 22,000 homes still rely on septic systems as the primary wastewater management method.
According to the Mornington Peninsula Shire’s wastewater management information, the Peninsula has more septic-reliant properties than any other Victorian council area, a figure that reflects the region’s historical development as a coastal and rural area well before reticulated sewer infrastructure reached most of it.
Types of Onsite Sewage Treatment Systems
Not all properties without a sewer connection use the same type of system. Several different onsite sewage treatment systems are approved for use in Victoria, and the type installed depends on the site conditions, soil type, and household wastewater output.
Conventional Septic Tank with Absorption Trench
This is the most common system on the Mornington Peninsula. The concrete or polyethylene tank holds and partially treats wastewater through settling and bacterial digestion. Clarified effluent then flows into perforated pipes in gravel-filled trenches, where the surrounding soil completes the treatment. It relies entirely on gravity and the soil’s natural capacity to absorb and filter effluent.
Aerated Wastewater Treatment System (AWTS)
An AWTS introduces oxygen into the treatment process to support aerobic bacteria, which break down waste more thoroughly than the anaerobic process inside a standard septic tank. The treated effluent is generally of a higher standard and can be dispersed in ways that a conventional system cannot. AWTS systems are used on sites where conventional septic and absorption trench systems are not suitable due to soil conditions, block size, or water table depth.
Mound System
A mound system raises the absorption area above the natural ground level using imported soil. It is used on sites with a high water table or shallow soil depth where a standard absorption trench cannot be installed at sufficient depth below the surface. The treated effluent is pumped up into the mound and dispersed through the imported soil profile.
Pump-Out System
A pump-out system stores wastewater in a sealed tank without any absorption field. The contents are removed by a licensed contractor on a regular schedule. These systems are used where no onsite disposal method is feasible, and they require ongoing pump-out costs rather than soil-based treatment.
Under Victorian regulations, any property installing or altering an onsite wastewater management system must obtain an A20 permit from the local council before work begins. The EPA Victoria A20 permit requirements set out what the permit covers, what the system must comply with, and how local councils enforce those requirements.
How to Tell What Wastewater System Your Property Uses?
To tell what wastewater system your property uses, look for septic access lids in the yard, check the property title documents, contact the local council’s environmental health team, or ask a licensed plumber to inspect the drainage infrastructure on site.
- Look for inspection lids in the yard. Concrete or plastic access lids at ground level or just above it, usually in the back or side yard, indicate a septic tank below.
- Check for a visible absorption field. A marked or fenced zone in the yard, or an area of noticeably greener grass running in a line, often indicates absorption trenches beneath.
- Review the title documents. The certificate of title and property information statement for a Victorian property typically notes whether the property is connected to the sewer system.
- Contact the local council. For properties on the Mornington Peninsula, the shire’s environmental health team holds records of all septic permits issued for a property. They can confirm whether a permit was issued and what system type was installed.
- Check water authority records. The relevant water authority for the area can confirm whether a sewer connection exists at the property address.
- Review property inspection reports. Any pre-purchase building and pest inspection on a septic property should identify the system type and its visible condition.
- Ask a licensed plumber. A licensed plumber familiar with the local area can inspect the visible drainage infrastructure and give a clear assessment of the system in use.
How to Inspect a Septic System Before Buying a Property?
To inspect a septic system before buying a property, engage a licensed plumber to assess the tank condition, service history, absorption field, and council compliance status before settlement is finalised.
How to inspect a septic system before buying a property walks through what a thorough pre-purchase inspection covers, including checking council records for the permit history, what a plumber looks for inside the tank and in the field, and what findings should prompt a price negotiation or a condition on the contract.
Buying a property with a failing or non-compliant septic system can create significant unexpected costs. A professional inspection before settlement is the most reliable way to know exactly what you are taking on.
What Happens When Mains Sewer Becomes Available?
When mains sewer becomes available at a property boundary, the owner is typically required to connect within a set period and formally decommission the existing septic system under Victorian regulations.
A septic system that is operating correctly can remain in service while no sewer connection is available. Once sewer reaches the boundary, the owner is generally required to connect within a set period and decommission the existing septic system properly.
The benefits of connecting to the reticulated sewer network are significant for property owners who have been managing a septic system for years:
- No more pump-out schedules or maintenance obligations for the onsite system.
- Elimination of the ongoing compliance and inspection requirements that apply to septic properties.
- Removal of the environmental and health risk associated with a failing absorption field.
- A positive impact on property value and ease of sale, particularly in areas where sewer is now considered standard.
Connecting to the sewer involves a licensed plumber coordinating the drain installation, tank decommissioning, and compliance certification. The process varies depending on the distance from the property to the nearest sewer main and the site conditions.
Need Help With Your Septic System on the Mornington Peninsula?
DCG Plumbing provides septic system inspections, assessments, and maintenance across the Mornington Peninsula. Whether you need a pre-purchase inspection, a condition assessment, or a pump-out and service, we give you a clear picture of what the system needs before any work is agreed.
For properties where sewer is now available and connection is the right next step, our sewer upgrade and connection service handles the full process from site assessment to compliance certification.
Call 0401 266 656 or contact us through the website to arrange a visit or a free quote.
Final Thoughts on Septic Tanks and Sewer Connections
Whether a property uses a septic system or connects to the mains sewer depends on its location, when it was built, and the state of local infrastructure. On the Mornington Peninsula, where more properties rely on onsite septic than anywhere else in Victoria, knowing which system a property uses, what type it is, and what condition it is in are all essential pieces of information for any homeowner or buyer. If you are unsure, a licensed plumber on the ground is the fastest and most reliable way to find out.
