Outdoor drains handle wastewater, rainwater or both, depending on the system. When they block, water may pond around buildings, carry contamination across paving or reveal a deeper sewer problem. Identifying whether the drain is sewer, stormwater or surface drainage is essential.
Before you worry
Do not assume every outdoor grate is connected to the same system. Stormwater and sewer drainage should normally remain separate, and the safe response depends on what the drain carries.
How to recognise the problem
- Water stands around an outside grate.
- A gully overflows when indoor fixtures are used.
- Bad sewer smells come from an inspection point.
- Rainwater remains long after a storm.
- Soil or paving sinks near a drain route.
Common causes
- Leaves, sand and garden debris.
- Grease or waste entering gullies.
- Roots in sewer or stormwater lines.
- Collapsed or displaced underground pipes.
- Incorrect gradients.
- Blocked municipal connections or downstream lines.
What you can safely check yourself
- Identify whether the water appears clean or contaminated.
- Remove loose surface leaves without reaching into the pipe.
- Stop indoor water use if a sewer gully is overflowing.
- Photograph the conditions and nearby inspection points.
What you should never do
- Do not enter manholes.
- Do not handle sewage without proper protection.
- Do not redirect contaminated water into stormwater channels.
- Do not excavate before services are located.
When to call a plumber
Call a plumber when wastewater is involved, the drain repeatedly overflows, the blockage is underground, or there are signs of pipe collapse. Stormwater problems may also require drainage or civil expertise depending on the system.
How professionals solve it
The line is traced, access points are checked and the obstruction is removed with mechanical or jetting equipment. CCTV inspection can locate roots, collapse or displaced joints. Surface levels and gradients may also need assessment.
How to prevent it happening again
- Keep leaves and soil away from grates.
- Do not pour grease or waste into gullies.
- Maintain accessible inspection points.
- Repair cracked pipes and root entry.
- Check outdoor drainage before the rainy season.
Frequently asked questions
Why does my outside drain overflow when I use the washing machine?
The appliance may discharge into a blocked shared waste line or gully.
Can rain cause sewer drains to overflow?
It can where stormwater incorrectly enters the sewer or where downstream capacity is restricted.
Who is responsible for a blockage outside my boundary?
Responsibility depends on the location and local authority rules. A plumber can help identify whether the problem is on private or municipal infrastructure.
Need help with a blocked drain?
Tell us which fixtures are affected, whether there is overflow and what you have already tried so we can help arrange the right drain response.