In a blocked stormwater system, rainwater coming from roof downpipes and other outside surfaces is involved. In contrast, a blocked sewer is characterised by household water from toilets, sinks, and baths. Clay pipes often become blocked in Sydney because they have short and unsealed parts that depend on mortar and rubber joints that eventually wear out. The ground moves, and roots find their way into the pipe through these weak joints to form a block.

At a Glance

• While stormwater systems transport clean rainwater into creeks, sewer systems transport contaminated water to treatment facilities.
• In clay pipes that are very popular in Sydney houses built before the 1980s, there is the risk of having weak connections between joints at intervals of 600 mm to 900 mm.
• Tree roots access clay pipes by tracing moisture vapour from small cracks in the mortar of the pipe.
• The signs of sewer blockages include internal noises and odours, while those of stormwater blockages are external surface flooding and overflowing of downpipes.
• Using water jetting to clear blockages only alleviates the symptoms and not the structural problem of root regrowth.

What Is the Difference Between Stormwater and Sewer Pipes?

The stormwater system is used for gathering storm runoff from rooftops, gutters, and other outdoor places, which then go through this system and are released untreated into nearby waterways or those around the Sydney Harbour area. The sewer system is used for collecting wastewater from toilets, showers, and washing machines, sending it off to be treated at water authority facilities.

In residential Sydney properties, these two underground networks operate under completely different principles:

Stormwater Drainage System

The main function of a stormwater system is to manage volumes in a gravity-driven way during rain storms. Once rain hits your roof, it moves through the gutters, through the downpipes and into the stormwater pipes buried underground. The pipes also carry stormwater from the grates on your driveway, your patio drains and garden pits. Since stormwater is presumed to be waste-free, it is directed to stormwater pipes in the town and rivers without any chemical treatments.

Sewer Drainage System

This is what is known as the sewer system (or the wastewater/sanitary drainage system). With every flush of the toilet, bath drain, or laundry machine operation, the generated waste flows through the sewer line that belongs directly to your property. This sewer line transports the grey water and black water from your house into the regional trunk mains of Sydney Water Company for further treatment.

According to the environmental laws that have been established by the New South Wales Environment Protection Authority (EPA), stormwater pipes and sewer pipes should not at all times be cross-connected. Sewage discharge into the stormwater pipes will affect the local waterways, whereas stormwater discharge into sewer pipes will strain the treatment facilities, especially during rainstorms.

Stormwater vs Sewer Drainage Systems Comparison

Feature	Stormwater System	Sewer System
Main Purpose	Directs rainwater runoff safely away from buildings	Transports domestic wastewater away from household fixtures
Inflow Sources	Downpipes, patio drains, garden pits, driveway channels	Toilets, showers, bathtubs, kitchen sinks, laundries
Treatment Destination	Untreated into local creeks, rivers, and coastal waterways	Transported to treatment plants managed by Sydney Water
Primary Blockage Causes	Leaves, garden soil, silt, tree roots, collapsed pipes	Tree roots, grease, wet wipes, paper buildup, cracked joints
Key Symptoms	Outdoor surface flooding, overflowing downpipes, garden pooling	Toilet backing up, gurgling drains, foul sewage odours indoors
Overflow Location	Lawn pits, driveway grates, downpipe bases	Overflow Relief Gully (ORG) outside the property
Typical Pipe Materials	PVC, vintage vitrified clay, concrete, corrugated plastic	PVC, vitrified clay, cast iron (in older character homes)
System Responsibility	Property owner (private lines) to Council curb/pit	Property owner (private lines) to Sydney Water main connection

How Can You Tell if a Blockage Is in the Stormwater or Sewer System?

This can be determined by checking the symptoms that occur with regard to which fixtures overflow. A stormwater blockage occurs whenever there is an occurrence of rain and causes problems like flooding in garden beds, overflowing downpipes, or flooding of driveways. The signs of sewer blockages occur inside the house and include sounds coming from the toilets, blocked showers, smells, or overflowing ORG outdoors.

Because the two networks serve different functions, their failure signs are distinct.

Stormwater Blockage Clues

• Weather Dependent: This problem occurs either during or soon after rain and is not visible during dry weather conditions.
• Accumulation of Water Outside: There is accumulation of water near garden beds, patios, or driveways.
• Overflowing Downpipes: Water flows out of the base of downpipes when they connect to the ground adapter.
• Spilling of Silt and Leaves: Silt and leaves spill out from lawn grates or stormwater pit tops.
• No Effect Inside: No effect on the toilets, baths, or kitchen sink inside the house.

Sewer Blockage Clues

• Disturbance in Indoor Plumbing: The water levels rise in the toilet bowl when you flush or water gathers in the shower area.
• Gurgling Noises: There is a bubbling of air in the toilet trap, the floor drainage system or the bathroom sink when another fixture gets flushed.
• Foul Odour of Sewage: Unpleasant smells emanate from the drains or from the edges of your home’s foundations.
• Activation of Overflow Relief Gully (ORG): This is the small drain near your house’s wall that overflows sewage on the ground. The ORG ensures that the wastewater is drained outside and does not overflow inside your home.
• Involving Multiple Fixtures: Using the washing machine leads to the flow of water to the bathroom floor drain.

Why Are Older Clay Pipes More Prone to Blockages?

Clay pipes that have been around for some time tend to get clogged due to their construction being made up of small pieces joined together by mortar or rubber joints. In the decades that pass, the soil in Sydney moves, resulting in the deterioration of these joints.

Vitrified clay (known as terracotta) was the drainage material of choice used on properties in Sydney during the 19th century and well into the 20th century. In older suburbs of Sydney, such as Paddington, Balmain, Newtown, Glebe, Leichhardt, Mosman, and Coogee, there remains a substantial number of residences with existing clay piping underground.

While clay itself is a durable material that does not rust or degrade when exposed to acidic soils, the structural vulnerability lies in how these pipe networks were constructed.

Clay pipe degradation process:

1. Ageing & Soil Movement: Cracking of joints or deterioration of mortar
2. Water Penetration: Water in vapour form penetrates soil surrounding the pipeline
3. Tree Roots: Roots in search of water penetrate through cracks
4. Inner Growth: Growth of roots increases inside the pipe; traps toilet paper
5. Water Flow Reduction: Slow movement of water, frequent clogging

The clay pipes used were made in small lengths from 600mm to 900mm each. In the case of 20 metres of piping, up to 30 pipe sections would be required, hence up to 30 joints. These joints were made using either sand cement or rubber rings.

Over time, several factors weaken these clay pipe networks:

1. Movement of Soil: The soils found in Sydney react to wetness by expanding and contracting when summer comes around. The constant movement of soil places strain on the stiff clay joints, resulting in cracks or dislodgement of mortar.
2. Brittleness: The clay is not flexible. If the roots of trees near the clay pipe press against the walls of the pipe, the clay cracks under pressure, or if heavy trucks pass over the pipe.
3. Offset: The movement of soil beneath the pipe leads to misalignment of the pipe sections. This creates a ledge for accumulation of solid matter, papers, and soil from the garden.

Just because a clay pipe line is old doesn’t necessarily mean that it’s going to break tomorrow, but each and every one of those joints that aren’t sealed is a potential weak point.

How Do Tree Roots Get Into Clay Drain Pipes?

The root system of trees penetrates clay sewer lines via the detection of tiny amounts of water vapour coming out of cracks and pores in the mortar used to connect sections of the sewer line. The roots follow the path of the water vapour and invade the cracks, multiplying quickly within the sewer line.

Hydrotropism is the term used to refer to the process that enables plants to move towards sources of water. The underground sewer lines have an unlimited supply of water, oxygen, and organic nutrients.

Once a crack appears in the clay joint or when the old cement mortar disintegrates, water enters into the soil. Trees like figs, liquidambar, jacaranda, eucalypts, and paperbarks, which are commonly found in Sydney gardens, direct their feeder roots towards the leakage point.

The invasion follows a predictable pattern:

1. Entering: Fine, hairlike strands of the roots penetrate the small hole in the mortar or in the broken body of the pipe.
2. Growth: Upon entering into the pipe, the roots get access to unlimited amounts of water and food. They grow quickly, expanding their diameter and pressing against the edges of the pipe hole, thus making it larger.
3. Trapping Waste: The root cluster inside the pipe serves as an underground filter. Inside the sewer pipes, it traps toilet paper, grease, and sanitary products, while inside the stormwater pipes it catches leaves, sticks, and garden soil.
4. Total Obstruction: Because of the waste getting caught behind the root cluster, the pipe’s capacity becomes blocked.

Blocking the clog with a mechanical root cutter can only be a temporary solution, as the open joint remains unaffected. However, unless the open joint is plugged, tree roots will eventually come back after a few months. For those who would like to see some of the lesser-known reasons for drain clogs, check out our guide on what causes drain blockages.

Can a Blocked Clay Pipe Keep Blocking After It Is Cleared?

Of course, if only the material causing the blockage is removed and not the problem with the structure of the clay pipe, then it is bound to get clogged up again. Plumbers use electric drain augers or high-pressure water jets to clean out roots and waste but do not repair the cracked joint or offset pipe.

It is common in Sydney homes to have a situation whereby a pipe is cleaned, functions for 3 to 6 months, and then gets blocked again. Cleaning a pipe makes the fluid flow, but it does not make any repairs to the pipe. In order to stop the continuous cycle of blockage, it is necessary for a plumber to assess the inside state of the pipe.

Does a CCTV Drain Inspection Find Clay Pipe Problems?

Certainly, CCTV drain inspection will be able to identify the problem areas of clay pipes using a high-definition self-levelling camera that is fed into the drainage pipe. This camera sends video feeds to the screen on the surface for viewing.

Guesswork in addressing underground drain problems results in wasteful excavation or improper solutions. A professional inspection using a camera offers visual proof of the state of the drain pipes.

During an inspection, a drainage specialist follows a clear process:

1. Access: The technician passes the fibre optic push rod camera into the drainage pipe via the clean-out access point, inspection opening, or overflow relief gully.
2. Video Footage: As the camera travels along the line, it provides video footage that captures all the surfaces of the pipes, including the walls, joints, and connectors.
3. Identification of Problem Areas: The transmitter located within the camera sends a signal that helps the plumber locate the exact depth and location of any crack or root growth in your property.
4. Diagnosis: From the video footage, it becomes clear if there is dirt buildup, a minor crack, displacement, or structural collapse of the pipe.

Based on these findings, the owner of the building can be able to determine whether high-pressure cleaning, relining, or excavation is needed.

When Does Pipe Relining Make Sense for Clay Pipes?

It is reasonable to reline a clay underground pipe if it shows signs of cracking, tree root intrusion or leaking at the joints while maintaining its shape structurally. Rather than excavating lawns, driveways, or tile floors from heritage-listed homes, plumbers line the existing pipe with a resin-soaked pipe.

The conventional technique for replacing pipes entails digging trenches that span the full length of the pipe that is to be replaced. This may prove challenging in many cases, where drainage pipes pass under permanent structures such as buildings, retaining walls, sidewalks, and landscape features.

The process involves insertion of an epoxy-coated flexible liner into the washed-out clay pipe. After inflation and curing of the liner, it becomes hard to form a structural pipe inside the pipe.

Key advantages of choosing pipe relining in Sydney:

• No Impact on Landscape: No damage to lawns, paths, driveways, or interior floors.
• Removal of Joints: The liner being seamless means there will no longer be joints where tree roots come in contact.
• Efficient Fluid Flow: The internal surface of epoxy resin is very smooth, which reduces friction, making flow easy.
• Durable: Good relining products are designed to last several decades.

Where a clay pipe has become so collapsed, squashed or structurally round that relining becomes impossible, then localised excavations and pipe replacement are the only practical choices left.

Who Is Responsible for a Blocked Stormwater or Sewer Pipe in Sydney?

In Sydney, the property owner is responsible for the stormwater and sewerage pipes on their private property up until the point of connection. Sewer mains are managed by Sydney Water in the public domain from the property trap or inspection point. The local council manages stormwater mains in the public domain.

Determining who pays for a blockage depends on where the physical fault or obstruction is located.

Sewer Line Responsibilities

• Private Property Lines: It is the duty of the property owner to maintain all plumbing within, branch lines underground, and the main private sewer line up to the boundary trap, riser or connection point marked by Sydney Water.
• Utility Lines: Sydney Water will be responsible for the maintenance of the main sewer system, collector mains and connections beyond the property boundary point.
• Problems with Neighbour’s Boundary: In case of blockage of the common sewer line between more than one property, then it will depend upon the fault position in relation to the property boundary.

Stormwater Line Responsibilities

• Private Property Boundaries: The property owner takes care of all roof guttering, downpipe work, garden drainage pits, surface drains, and underground drains up to where they meet the street kerb or stormwater pit owned by the council.
• Municipal Council Main Drainage: The municipal council operates the public street guttering, kerb inlet work, and large underground stormwater mains under the public roads and parks.

In case you think that the obstruction is in the main sewage line of Sydney Water, then a plumber can check the connection point using a CCTV camera to determine if the problem lies in your personal property or in the public system.

How Emergency Drains Can Help

At Emergency Drains, we specialise in handling any kind of drainage issues in Sydney. If you have any problem, whether it is constant sewerage backup, water overflow from the stormwater pit, or old clay pipes under the drive, we are here for your help.

Our drainage services include:

• Drain Jetting with High Pressure: Effective cleaning of silt, grease and other obstructions in blocked stormwater and sewer pipes.
• CCTV Drain Inspection: Conducting video inspections to detect cracks, root intrusion, and offsets in stormwater and sewer pipes without excavating.
• Root Intrusion Cleaning: Cleaning tree roots from clay and PVC drainage pipes.
• Pipe Relining: Repair of damaged clay pipes using trenchless methods to stop future intrusion by roots.
• Blocked Stormwater Drain Services: Restoring proper flow of water with our blocked stormwater drain services.
• Sewer Pipe Repair/Replacement: Excavating and replacing sections of pipes that are too badly damaged for relining.

We focus on locating the actual cause of your drainage issue so you can make informed decisions about your property.

Resolving Your Clay Pipe Issues

Realising the distinction between stormwater and sewer systems forms part of the solution when dealing with drainage problems at properties in Sydney. Although vitrified clay pipes that have been used for many years to connect Sydney homes are very resilient, their many joints make them susceptible to soil movement and damage by tree roots.

While plunging the toilet or using an instant cutout for drains could clear up any immediate clogs, it will take the correct diagnostics to determine any problems with the structure of the pipes themselves. Slow drainage, backups, odour issues, or even flooding in the home can be investigated with a camera.

In case you are experiencing repeated blockages, or suspect tree roots have found their way into your pipes, or just want an evaluation of the state of the clay pipes on your property, get in touch with us at Emergency Drains.

Frequently Asked Questions

How do I know whether I have a stormwater or sewer blockage?

Identify what plumbing fixture is affected. In case there is backing up of water into toilets, showers, or floor wastage systems within the house, then the problem lies within your sewerage system. If water puddles within your garden beds, overflows within the downpipes or drains into your driveway, then the problem lies within your stormwater system.

Can tree roots get into old clay stormwater pipes?

Yes, since tree roots can easily access the stormwater pipes that are made of clay through weak mortar joints, small cracks, and loosely fitted pipes. This is because the stormwater pipes are nearer to the ground level, where there is moisture during rainfall.

Are homeowners responsible for blocked sewer pipes in Sydney?

The property owners are responsible for the maintenance of all private sewer pipes within the property lines until they reach the designated connection point. Sydney Water is responsible for the public main sewer system which runs beyond the connection point.

Can a CCTV drain inspection show whether clay pipes need repair?

Yes. CCTV drain inspection entails the use of a camera that transmits live video images from the drain. This enables the assessment of structural aspects such as cracks, open joints, tree root penetration, and pipe sags or collapse, among others.

Is pipe relining suitable for old clay drainage pipes?

Pipe relining can be used on cracked, open-joint, or root-entrapped clay drainage pipes, provided that the pipe still has the basic circular form. The relining involves installation of the epoxy resin liner inside the old clay pipe to form a seamless lining that will prevent roots from entering the pipe.