VIC Shared or single owner costs? - Combined sewer - Replacement of section servicing one owner's property

[LuckyFelicity]

I live in a semidetached house # 2 X St in Victoria.

I own, together with the owner of 2A X St, a combined sewer that is in the middle of my neighbour’s back yard, see the attached Yarra Valley Water Property Sewer Plan #212466 and attached diagram provided a few weeks ago by a plumber to whom I described the circumstances.

The diagram illustrates the sewer system for both properties more accurately, I believe.

A section of the original clay pipe sewer system that services my residence, only, and which is under a tree in 2A’s back yard close to the dividing fence, see the diagram, is blocking with roots of the tree above it and needs to be replaced, see below. This section of the sewer joins the combined sewer in the centre of 2A’s back yard, see the diagram.

A plumber who inserted a camera and jet cleared roots of the tree from this section in April 2023 advised then that the sewer would block again with roots, possibly within 12 to 18 months. Water levels in my toilet have intermittently for approximately five months (beginning approximately 2 years after the previous blockage), indicated blockage of the sewer. As the tenant at 2A has informed me that they have not had any indication of blockage or malfunction of their toilet I am certain, after speaking with a plumber who, after discussion with me, drew the attached diagram, that the section of the sewer that services my residence and which is in 2A’s back yard, is once again blocking with roots of the abovementioned tree. The section of the clay sewer pipe servicing my residence between my toilets and the boundary fence was replaced with a new PVC pipe in December 2004, see the updated/amended YVW Property Sewer Plan attached.

The plumber who cleared the blockage in April 2023 advised on the Invoice for that service, which was addressed to “The Owners 2 & 2A XXXXXXXXXXXX, 2 & 2A XXXXXXXXX VIC”, that the charges were to be shared: “COMBINED DRAIN 50% shared cost for 2 & 2A”. He also advised on the Invoice “Please note, sewer will continue to block therefore recommend section is replaced on combined drain [shared cost])” and “found cause of blockage to be a root incursion through a break in the earthenware sewer drain, this is located in 2A”.

The plumber who drew the attached diagram, with whom I recently discussed seeking a quote, advised me, contrary to the April 2023 plumber’s advice, that, as the affected section of the sewer system services my property only, I would have to pay the full cost of the plumbing work involved in quoting and replacing the affected section.

As I have had contradictory advice from two plumbers I am, therefore, seeking legal advice as to whether both owners are liable to share the cost of quotes and replacement of the affected section of the sewer or whether I, as owner of 2 XXXXX St, the property which is serviced by the blocking section of the sewer, am liable for the total plumbing costs.

It would seem unfair to me that I would have to pay the full cost as (a) the blockage is in 2A’s back yard by roots of a tree planted by an owner of 2A and (b), as I do not own that backyard, I have no control over land management affecting the condition and functioning of the pipe, such as the planting of a tree directly above it. The sewer system in 2A’s back yard has previously blocked twice under the current ownership of 2A and once under the ownership of a previous owner of 2A. On those three occasions the blockages were caused (secondary cause) by roots of trees in the back yard of 2A.

There has been difficulty for a number of years between the current owner of 2A and me over removal of problem trees. He did not act on the April 2023 plumber’s advice to remove the tree then and, with my agreement, replace the affected section of the pipe. However, he has fortunately now agreed to remove the tree, “if necessary, to enable replacement of the blocking section of the sewer” but has advised that he does not intend to pay a half share of the replacement plumbing costs.

I would be grateful for your response.

Thank you.

 

[Atticus]

I’ll step you through the legal principles in Victoria (Australia) that apply, so you can see where the responsibility might fall and how to approach it. C/O Chatgpt.com

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1. Definitions in Victorian Law​

• Property drains (house drains): Pipes that carry sewage from your house up to the point of connection with the water authority’s sewer (usually the property connection branch or “sewer branch”).
• Combined private drains: Where two or more properties share a single private sewer line before it connects to Yarra Valley Water’s assets. These are jointly owned by the benefiting properties, and both parties are usually equally responsible for upkeep and repair.

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2. Key Distinction​

From what you describe:

• The affected pipe section is in 2A’s backyard, but it services only your property (2).
• It connects into the “combined drain” in the middle of 2A’s backyard, which is then shared by both properties.

So the issue boils down to:

• Is the affected section considered part of the shared combined drain, or is it treated in law as your exclusive property drain?

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3. Why Plumbers Disagreed​

• Plumber A (April 2023): Treated the whole line in 2A’s backyard as part of the combined drain, therefore shared responsibility.
• Plumber B (diagram): Treated the branch that only services your house (before it joins the shared section) as your sole responsibility, even though it physically runs through 2A’s land.

Both positions can be argued under plumbing rules, which is why you’ve had contradictory advice.

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4. Legal Responsibility​

• Victorian Water Act 1989 & Plumbing Code: Responsibility is generally divided by whether the pipe services one or multiple properties.
  • If the pipe services only one property, the legal responsibility for repair usually lies with that property’s owner — even if the pipe physically runs under a neighbour’s land.
  • If the pipe services two or more properties (combined drain), then responsibility is shared equally, unless there’s an agreement stating otherwise.
• Trees & root damage: Even if the pipe is yours, you may have a legal argument that the tree roots from 2A caused the damage/blockage. In principle, owners are responsible for nuisance/damage caused by vegetation on their land. However, proving that in practice, and recovering money, often requires mediation or court action.

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5. Fairness vs Legal Liability​

I agree it feels unfair:

• The pipe is on your neighbour’s land.
• The blockage was caused by his tree.
• You can’t access/manage the risk without his cooperation.

But strictly in law:

• Unless the section of pipe is formally recognised as a combined drain (YVW can sometimes confirm this from the Property Sewer Plan), you are likely legally responsible for the replacement cost.
• You could, however, argue for a contribution from 2A on the grounds that his tree directly caused the damage. That would move it into a dispute resolution process rather than a plumbing responsibility one.

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6. Practical Steps​

1. Confirm with Yarra Valley Water: Ask them whether the branch pipe is classified as a combined drain or your private property drain. They hold the definitive plans.
2. Get written plumbing advice: A licensed plumber can submit a “sewer encroachment” note clarifying which part is considered shared.
3. Neighbour dispute resolution:
   • If YVW says it’s your pipe, you could still seek cost-sharing with 2A under the principle of tree root damage.
   • Start with negotiation/mediation (the Dispute Settlement Centre of Victoria is free and very effective).
   • If that fails, VCAT is the forum for cost-sharing or nuisance/tree-root disputes.

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7. Summary​

• Most likely legal position: You are responsible for the section of pipe because it services only your house, even though it runs under 2A’s backyard.
• Possible contribution from neighbour: You may have a claim that their tree caused the damage, but that’s a separate legal argument (nuisance/property damage), not an automatic cost-sharing under sewer law.
• Best next step: Confirm classification of the pipe with Yarra Valley Water, then decide whether to pursue negotiation/mediation with 2A for contribution.

 

[LuckyFelicity]

Thank you, Law Answers.
I have for a number of weeks sought an answer from various sources, to no avail. My toilet continues to indicate blocking, with a complete blockage likely at some point.
I am very grateful to at last receive clear, comprehensive legal advice.
I will first seek clarification from YVW as to whether the branch pipe is classified as a combined drain or my private property drain.
LuckyFelicity