Your property has two entirely separate drainage systems running underground — the stormwater system and the sewer system. They look similar from the surface, they're both pipes carrying water, but they serve fundamentally different functions, run to different destinations, and — critically — when they're blocked, different parties are responsible for fixing them.
Confusing the two can lead to calling the wrong service, misunderstanding who should pay for repairs, and occasionally making drainage problems significantly worse by connecting things that shouldn't be connected. Here's everything a Newcastle homeowner needs to know about the difference.
What the Stormwater System Does
Your stormwater system collects rainwater runoff from your property — roof water from gutters and downpipes, surface water from driveways and paved areas, and drainage from garden areas — and carries it away from your property through underground pipes to a legal point of discharge. That discharge point might be the street gutter, a stormwater channel, a creek, or a stormwater detention basin.
Stormwater carries no sewage. It's rainwater mixed with whatever it picks up from your roof and paving — dust, leaf matter, bird droppings, and in urban areas, small quantities of pollutants from vehicles. It goes directly to waterways, which is why it's kept separate from sewage.
What the Sewer System Does
Your sewer system collects wastewater from every toilet, sink, shower, bath, dishwasher and washing machine in your home and carries it to Hunter Water's sewer main under the street. From there it travels to a sewage treatment plant where it's treated before being released or reused.
The sewer system operates under completely different conditions to stormwater — it carries organic waste, needs to maintain consistent flow, and must be kept completely separate from stormwater to prevent treatment plant overload during rain events.
How to Tell the Difference on Your Property
| Feature | Stormwater | Sewer |
|---|---|---|
| What drains into it | Roof water, surface water | Toilets, sinks, showers, appliances |
| Drain covers | Open grates, kerb inlets | Sealed inspection covers |
| Smell when opened | No smell (usually) | Sewage smell |
| Water runs during rain | Yes | No (shouldn't) |
| Connects to | Street gutter / waterway | Sewer main under street |
| Who maintains | Property owner (private drain) | Property owner (private drain) / Hunter Water (public) |
Who Is Responsible for What in Newcastle
For stormwater drainage, the property owner is responsible for all stormwater pipes and infrastructure within the property boundary. Council may have responsibilities for street-level stormwater infrastructure, but your downpipes, underground stormwater lines and drainage pits are your responsibility.
For sewage drainage, the property owner is responsible for the pipes within the property boundary up to the point where the private drain connects to Hunter Water's sewer main — typically near the front property boundary. Hunter Water is responsible for the sewer main itself. The boundary trap (usually found near the front fence) is the demarcation point.
The Serious Problem: Cross-Connections
Cross-connection — where stormwater enters the sewer system or sewage enters the stormwater system — is one of the most serious drainage problems a Newcastle property can have. It's also surprisingly common in older properties where informal plumbing connections were made without permits, or where decades of ground movement have caused pipe failures that created unintended connections.
Stormwater entering the sewer system causes sewer overflow during rain events — the treatment plant can't handle the extra volume and overflows at the lowest points in the system (which may be your property). Sewage entering the stormwater system sends untreated waste directly to waterways — a serious environmental and legal issue.
If your property floods during rain events, if your sewer backs up specifically during rainstorms, or if a smoke or dye test reveals unexpected connections, call a plumber for a full drainage investigation.
Can I connect my downpipes to the sewer in Newcastle?
No — connecting roof stormwater to the sewer system is illegal in NSW and specifically prohibited by Hunter Water. Roof water connected to the sewer massively increases sewer flow during rain events, contributing to sewer overflow. If your property has historical downpipe connections to the sewer (common in some older Newcastle homes), these should be disconnected and redirected to the stormwater system.
My backyard floods every time it rains — is that a stormwater problem?
Almost certainly yes. Backyard flooding during rain events is caused by inadequate stormwater drainage — blocked stormwater pits, undersized pipes, insufficient drainage capacity, or low points in the landscape without adequate drainage. A plumber can assess the stormwater system, identify blockages or inadequacies, and recommend solutions ranging from a simple drain clean to additional drainage capacity.
📞 Need a plumber in Newcastle? Call 0491 570 006 for same-day service across Newcastle and the Hunter region.