Why do stormwater drains overflow?

Stormwater is not your sewer

They are separate systems. Stormwater takes roof and surface water from downpipes, grated drains and pits to a legal discharge point. Sewer takes waste water to treatment.

If your yard floods but the drains inside the house are fine, the problem is stormwater, and it is a different job with different equipment.

The grate you can see is rarely the problem

People clear the leaves off the pit, watch it still overflow, and conclude the drain is broken. Usually the pit is just the entry point and the restriction is somewhere along the line between there and the discharge point.

Silt settles in flat sections. Roots get in at joints. A section under a driveway gets crushed. None of that is visible from the grate.

Gold Coast weather makes it worse

Our rain arrives in short heavy bursts rather than steady drizzle. A line that copes fine most of the year can be overwhelmed in minutes by a summer storm, and that is exactly when you find out it was already half blocked.

This is why stormwater is the one drainage job genuinely worth doing before you need it. A pit half full of silt in September is a flooded garage in January.

Where you live changes the cause

• Canal estates: sand migrating into the line, flat falls, tidal outfalls
• Bushland-backed blocks: heavy leaf and bark load in pits
• Acreage: silt off unsealed driveways and bare ground
• Sloped blocks: fast runoff carrying debris down into pits from above
• Older suburbs: root intrusion into shallow, jointed stormwater lines

When it is urgent

Water pooling in the yard is a nuisance. Water running toward the house, into a garage, or under a building is not, and that one should not wait for the next dry spell.