How 376 old, leaking septic tanks in Manningham are contaminating Melbourne waterways

Septic tanks being illegally discharged into stormwater drains have helped push the risk to human health from water channels like Mullum Mullum Creek to high, with 376 Manningham properties deemed to be non-compliant.

Manningham Council has given these homeowners – a number within Park Orchards – an ultimatum: either pay up to connect to the new sewerage system being installed next year or pay the council to continue.

💩 What is a septic tank? A septic tank is an onsite wastewater management system which treats or otherwise houses wastewater from a property, including water and human waste from showers, toilets and sinks.

• Pumping out a septic tank generally costs between $300 and $800 per service – or about $320 if serviced every three years and calculated as an annual cost.

🚽 Forcing safer flushes: On November 25, Manningham Council voted to approve an updated Onsite Wastewater Management Plan, detailing actions to take until 2030 that included council officers investigating the legality of charging residents who do not choose to connect to the main sewerage line.

• The council will also continue to advocate for Yarra Valley Water to carry out the connection themselves if the owner has failed to comply.

✉️ Naughty neighbours: In areas which recently received new sewerage systems, 577 properties have decided to keep using their old septic tank systems.

• However, inspections by Yarra Valley Water have found 376 are non-compliant as they send wastewater into stormwater systems due to their extended age and poor installation practices.

🤢 What’s the harm? Council’s plan outlined the risk to human health from waterways near these property owners was currently at a high level.

• Older or poorly installed septic tanks can be a risk to human health and the environment, with potential impacts including exposure to dangerous microorganisms that can cause a range of illnesses or viral infections.

• “It’s not a happy environment for the little fish or for anyone going down to the Mullum Mullum Creek or the Yarra,” said Manningham councillor Andrew Conlon.

💰 Switch vs stay? Many homeowners retain their septic tank instead of switching over to sewerage as water bills increase, while costs to remove their existing septic tank and connect to the main sewerage can range from $3,000 to $15,000.

⏭️ What’s next? Yarra Valley Water (YVW) is currently working on designs for a new sewerage system for Park Orchards and parts of Ringwood North, with construction expected to commence in late 2027.

• Manningham Council deputy mayor Deirdre Diamante said she was “cross” to learn so many property owners decided to retain non-compliant septic tanks rather than switch to the safer option, calling on the community to take better care of the local environment.

• 🗣️“It’s an environment we need to have for our children and grandchildren and great-grandchildren.”