How to Inspect Stormwater Drains Properly

A wet patch beside the driveway, water ponding after a shower, or a downpipe that backs up in heavy rain can all point to the same issue: the stormwater system is not moving water where it should. Knowing how to inspect stormwater drains helps homeowners and project teams spot obvious problems early, but it also shows where a professional CCTV inspection is needed before excavation, construction or expensive repairs begin.

Stormwater drains carry rainwater from roofs, gutters, yards and hard surfaces to an approved discharge point. They are separate from wastewater drains, which carry water from toilets, sinks and other plumbing fixtures. Confusing the two can lead to poor decisions on site, particularly when investigating a blockage or planning new building work.

Start with a safe, above-ground inspection

The most useful first check is usually above ground. Walk the route water takes from the roof and around the property after rain, or use a hose carefully where practical. Look for where water pools, overflows or disappears slowly. The goal is not to prove the pipe is clear, but to identify symptoms and narrow down the likely location of a fault.

Check gutters, downpipes, rainheads and leaf guards first. A blocked gutter outlet or a downpipe full of leaves can look like an underground drainage failure. Clear accessible debris using safe ladder practices, but do not work at height in wet conditions or attempt to reach areas that cannot be accessed safely.

At ground level, inspect grates, sumps, channel drains and catch pits. Remove loose leaves, mulch and surface rubbish that prevent water entering the grate. If a grate is covered by soil, pavers or landscaping, it may be unable to collect runoff when it matters most. Take photographs before moving anything, especially on a commercial site or where drainage condition may affect a building project.

Also look for changes in the ground around likely pipe routes. Soft or sunken areas, unusually green grass, washouts near a driveway, and water emerging from a retaining wall can indicate a damaged or disconnected pipe. These signs are not conclusive on their own. Water can travel through soil from a different point, which is why accurate drain location and camera evidence are valuable before digging.

How to inspect stormwater drains at access points

Stormwater systems may have inspection openings, sumps or access points with removable lids. These are the best places to observe the drain without disturbing pipework. Only open covers that are safe to lift and clearly within your property. Covers can be heavy, unstable or located near traffic, and open chambers create a fall hazard.

Once an access point is open, look for standing water, silt, leaves, tree roots, broken concrete, displaced pipe joints or visible debris. Water sitting in a chamber is not always a problem. Some sumps are designed to retain a small amount of water, while a pipe at a low point may drain slowly. What matters is whether the system is functioning under rainfall and whether water is backing up above the expected level.

A simple flow check can be useful. Run water into one downpipe at a time and observe the receiving sump or outlet where accessible. This can help identify a completely blocked branch or confirm that a particular downpipe is not connected as expected. Avoid sending large volumes of water into a system already overflowing, and do not use harsh chemicals. Chemical drain cleaners rarely solve a stormwater fault and can create risks for people, pipes and the environment.

Do not enter a drain, chamber or manhole. Confined spaces can contain dangerous gases, low oxygen and sudden water flows. Inspection is carried out from the surface using the appropriate equipment.

Know what common symptoms mean

Different symptoms point to different likely causes. A single downpipe overflowing while other outlets work normally may suggest a local blockage in that branch. If several areas back up during heavy rain, the issue could be a larger obstruction, insufficient capacity, a damaged main line or a downstream outlet problem.

Tree roots are a common cause of stormwater drainage issues, particularly in older properties with earthenware or concrete pipes. Roots often enter through joints or cracks, then catch leaves and sediment until the pipe restricts or blocks. Removing roots may restore flow temporarily, but the pipe condition needs to be assessed. If a joint is open or the pipe has fractured, roots are likely to return.

Silt is another frequent issue. Runoff from unsealed areas, garden beds, construction activity or sloping sites can carry sediment into sumps and pipes. Silt may reduce capacity gradually, so the system seems acceptable in light rain but fails during a major downpour. Cleaning is often part of the solution, but the reason sediment is entering the system should also be addressed.

Crushed pipes, poor falls, displaced joints and undocumented alterations are more difficult to diagnose from the surface. These faults may be associated with vehicle loading, ground movement, previous excavation or older installation methods. Guessing at their location can result in unnecessary digging across lawns, paths or driveways.

When a CCTV drain survey is the right next step

A CCTV drain survey uses a purpose-built camera to inspect the inside of the pipe. It provides direct evidence of the pipe’s condition, route and defects, rather than relying on symptoms alone. For a blocked or slow stormwater drain, this can identify whether the cause is roots, debris, a collapse, a broken joint, a flat section or another obstruction.

Camera inspection is especially useful when the problem keeps returning after cleaning. Repeated blockages generally indicate more than a one-off buildup of leaves. It is also the sensible next step where there are signs of leakage, subsidence or unknown drainage routes, or where work is planned near underground services.

For homeowners, a survey can provide clarity before approving repair work. For architects, builders and surveyors, it can establish existing drainage information needed for design, construction planning or a property transaction. The level of reporting required depends on the purpose. A basic fault investigation is different from a documented survey required to support a consent or works over application.

A proper inspection should record meaningful findings, including the pipe material where identifiable, condition, defects, access points and the approximate location of issues. Drain location equipment can then be used to trace the camera from above ground, helping establish where the pipe runs and where targeted repair may be required.

Inspect before building, excavating or buying

Drainage inspection is not only for active blockages. Before building an extension, installing a pool, constructing a driveway or carrying out excavation, it is prudent to establish where stormwater pipes run. A pipe may cross an area that appears clear, and damage during earthworks can create a costly problem that only becomes obvious in the next heavy rain.

This is particularly relevant where work may occur over council or Watercare-owned assets. Building over these assets can require a works over approval and supporting drainage information. The required evidence varies by project, so it is best to identify assets and their condition early rather than discovering them after plans are developed or work has started.

Pre-purchase drainage inspection can also be worthwhile for older homes, properties with mature trees, or sites showing damp areas and poor surface drainage. A camera survey will not remove every property risk, but it can reveal underground faults that are difficult to see during a standard viewing.

What not to do during a drain inspection

It is tempting to push a hose, rod or improvised tool into a blocked stormwater pipe. This can compact debris, damage a weak pipe or make later camera access more difficult. High-pressure water jetting is effective in the right hands, but it should follow an assessment where pipe condition is uncertain. A badly damaged or collapsed pipe will not be repaired by forcing water through it.

Avoid assuming a stormwater outlet can be redirected into the wastewater system, onto a neighbour’s property or across a footpath. Stormwater discharge and connection requirements matter, and changes should be assessed properly. Surface flooding is often a sign to investigate the full drainage layout, not simply create a new path for the water.

If water is threatening a building during severe weather, focus first on immediate safety. Keep people away from open pits and electrical hazards, protect entry points where possible, and arrange assessment once conditions allow. Photographs and notes about where water appeared can be very useful for diagnosing the cause later.

A stormwater drain is out of sight for most of its life, but it should not be out of mind when warning signs appear. A careful surface check can identify simple maintenance issues; accurate CCTV inspection can turn an underground guess into a practical repair or construction decision.