What Causes a Blocked Stormwater Drain?

Blocked stormwater drains are usually caused by leaf debris, tree roots, or pipe collapse.
Signs include slow water runoff, pooling near grates, gurgling sounds, or water backing up after rain. To fix it, clear surface debris, check for pipe blockages, and if issues persist, consider installing a French drain to redirect excess water away from your home’s foundations.

In heavy rain, your stormwater system should send water safely away from your property. But when drains block, water backs up fast flooding gardens, damaging foundations, and seeping into basements or subfloors.
For Wollongong homes, especially those on sloping blocks or clay-heavy soil, blocked stormwater drains are a recurring problem.

Whether your grate is overflowing, or your backyard pools like a swamp every storm, this guide breaks down what causes the blockage, how to clear it, and when it’s time to install something smarter like a French drain system.

Common Causes of Blocked Stormwater Drains in Wollongong

1. Leaf Litter and Garden Debris

During storms, leaves, bark, and mulch wash into surface grates, forming a natural barrier. Without regular cleaning, these blockages build up fast especially in leafy suburbs like Keiraville, Figtree, or Mt Keira.

2. Tree Root Invasion

Mature trees send roots into stormwater lines looking for moisture. Over time, these roots can crack PVC or clay pipes, restrict water flow, and trap debris inside.

3. Pipe Collapse or Silt Buildup

Older stormwater systems, particularly in pre-2000 homes, may suffer from collapsed pipes, poor fall angles, or sediment accumulation. These faults often go unnoticed until the first major rainfall event.

4. Poor Surface Grading

If your yard doesn’t slope away from your house, water naturally collects near walls and grates. Even a working pipe can’t compensate if the surface doesn’t allow flow.

Signs Your Stormwater Drain is Blocked

• Surface water pooling near grates or downpipes
• Gurgling or bubbling sounds during rain
• Water overflowing from gutters or pits
• Soggy lawns or spongy soil days after rain
• Basement or garage flooding after storms

First Steps to Clear a Blocked Stormwater Drain

1. Remove Surface Debris
Clear grates, pits, and downpipe guards of leaves and silt. In many cases, the blockage is just under the cover.

2. Flush the Line
Use a high-pressure hose or jetter to clear shallow blockages. If the system backs up, stop—further pressure may worsen a collapsed section.

3. Use a Drain Camera
A licensed plumber can inspect stormwater pipes using a CCTV drain camera to identify cracks, blockages, or misaligned joins.

4. Clear Tree Roots Professionally
If roots are present, pipe relining may be the best long-term solution—sealing the pipe without excavation. If you’re unsure, our Wollongong drainage specialists can diagnose and repair blocked systems fast.

When to Install a French Drain

French drains are subsurface drainage systems that redirect water away from your property. They consist of a gravel-filled trench with a perforated pipe, laid at a slight gradient to carry water toward a discharge point.

Ideal Situations for a French Drain:

• Yard flooding despite working downpipes
• Water pooling near retaining walls or foundations
• Driveway runoff overwhelming surface drains
• Sloped blocks where water channels downhill

Our team regularly designs and installs custom French drain systems in Wollongong to suit local soil, slope, and rainfall conditions.

How a French Drain Compares to Standard Stormwater

Feature	Stormwater Drain	French Drain
Handles Roof Runoff	✔️	❌
Handles Groundwater	❌	✔️
Installed Under Grass	❌	✔️
Requires Surface Inlet	✔️	Optional
Best For Surface Flow	✔️	Partial
Best For Subsoil Drainage	❌	✔️

Preventing Future Blockages

• Clear gutters and grates before storm season
• Install leaf guards on downpipes
• Schedule annual drain jetting or camera inspections
• Avoid planting trees near underground lines
• Ensure lawn gradients slope away from structures

Final Advice for Wollongong Homeowners

Blocked stormwater drains aren’t just inconvenient—they’re a risk to your home’s structural integrity. Flooded footings, damp basements, and repeat water pooling all point to an overloaded or failed system.

If clearing debris doesn’t fix it, there’s likely a deeper issue inside your pipes—or in the way your property handles water. That’s where expert design and drainage solutions make the difference.

Don’t wait until the next flood to act. If your yard is holding water, your pits are overflowing, or you suspect tree roots in your lines, book an inspection.
We’ll identify the fault, and if needed, design a French drain or pipe solution tailored to your site.