Water pooling around your stormwater grate after rain usually means one thing: leaves, silt or rubbish have built up in the pit or pipe, and the water has nowhere to go. Left alone, a blocked stormwater drain can flood your yard, undermine paths and driveways, and push water towards your house. That’s why it pays to know how to unblock stormwater drains yourself.

The good news is that most blockages near the grate can be cleared yourself in under an hour with a hose, gloves and a drain rod. This guide covers how to tell your drain is blocked, the steps to clear a blocked drain, when the job needs a licensed plumber, and how to stop the same blockage coming back every wet season.

Signs Your Stormwater Drain Is Blocked

Catching a blockage early is much cheaper than repairing water damage. Look out for these warning signs:

Water pooling around the grate that takes hours to drain after rain stops.
Overflowing gutters or downpipes, even when the gutters themselves are clean. This often means the pipe below is backed up.
A musty or rotten smell from the pit, caused by trapped leaves and stagnant water.
Gurgling sounds from the grate or downpipes as water struggles past a partial blockage.
Soggy lawn or sinking ground along the line of the pipe, which can point to a cracked or root-damaged pipe.
Silt, mud or leaf litter visible on top of or just below the grate.

What Causes Stormwater Drain Blockages?

Most blockages start at the inlet, where rainwater carries loose material straight through the grate.

Leaves and garden waste. Autumn leaf drop and lawn clippings mat together and form a dam inside the pit.
Silt and soil. Runoff from garden beds, unsealed driveways and nearby building sites settles in pipes and hardens over time.
Rubbish. Plastic bags, bottle caps, wrappers and toys wash in from the street or yard.
Tree roots. Roots find their way into joints and cracks in older clay or concrete pipes and grow into a dense mat.
Damaged pipes. Cracked, sagging or collapsed pipes trap debris and let soil fall in from outside.

The first three causes all enter through the grate. That is why stopping debris at the inlet, covered later in this guide, prevents most repeat blockages.

Before You Start: Safety and Responsibility

Stay Safe

Never work on a drain during a storm or flood. Fast-moving water and hidden open pits can cause serious injury.
Wear heavy-duty gloves, eye protection and closed shoes. Stormwater debris can hide broken glass, sharp metal and bacteria.
Lift heavy grates with your legs, not your back, or use a grate lifter. Heavy-duty cast-iron grates can be surprisingly heavy.
Never climb into a pit. Deep pits are confined spaces and can contain low oxygen or harmful gases.
Don’t pour chemical drain cleaners into stormwater drains. In Australia, stormwater is a separate system from sewage and flows untreated into creeks, rivers and beaches.

Who Is Responsible for the Drain?

In most areas, the property owner is responsible for stormwater pits and pipes on their land, up to the point where they connect to the council’s kerb outlet or drainage line. Street grates, kerb inlets and public drainage pipes are usually the responsibility of the local council or water authority. If the blockage is in a public drain, report it to your council rather than trying to clear it yourself. Rules vary between councils, so check with yours if you are unsure.

How to Unblock Stormwater Drains: Step by Step

Work on a dry day if you can. You will need heavy-duty gloves, a bucket, a garden trowel or small shovel, a garden hose with a jet nozzle, and a drain rod or hand auger (both available from most hardware stores).

Inspect the grate and pit. Look for leaves, silt or rubbish on the grate surface and in the pit. Shine a torch into the outlet pipe to see how far the blockage goes.
Clear the grate surface. Sweep or scoop away everything sitting on top of the grate so water can reach the pit again.
Lift the grate and empty the pit. Remove the grate and scoop out leaves, silt and rubbish by hand or with a trowel into a bucket. Put organic matter in your green bin and rubbish in general waste, never back in the gutter.
Flush the line with a hose. Push the hose a short way into the outlet pipe and turn it on full. If the water drains freely, the blockage is cleared. If water rises in the pit, keep going.
Break up deeper blockages with a drain rod or auger. Feed the rod into the outlet pipe, turning it clockwise as you push. When you feel resistance, work it back and forth to break up or hook the blockage, then pull out what you can.
Flush again and test. Run the hose for several minutes. Steady flow with no rising water means the pipe is clear.
Check where the water comes out. Look at the kerb outlet or downstream pit to confirm water is flowing out freely.

If water still backs up after these steps, the blockage is likely deeper in the line, caused by roots, or the result of a damaged pipe. That is the point to call a professional.

When to Call a Licensed Plumber

Call a plumber when DIY clearing does not restore flow, or when you see signs of pipe damage. Repairs and alterations to stormwater pipes are regulated plumbing work in every Australian state and territory, so they must be done by a licensed plumber or drainer.

Call a professional if:

Water still backs up after you have rodded and flushed the line.
The same drain blocks again within weeks.
You suspect tree roots, or the ground above the pipe is sinking or always wet.
Several drains on your property are slow at the same time.
The pit is too deep to reach safely.

A plumber will usually start with a CCTV drain camera to find the exact cause and location. Common fixes include high-pressure water jetting to blast out silt and roots, root cutting, and pipe relining or excavation to repair cracked or collapsed sections.

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How to Stop Your Stormwater Drain Blocking Again

Unblocking a drain fixes today’s problem. Preventing the next blockage means keeping debris out of the pit in the first place.

Simple Maintenance Habits

Clear leaves and litter from grates before forecast heavy rain and after storms.
Clean gutters and downpipe leaf guards at least twice a year, more often under trees.
Keep mulch, soil and gravel away from grates, or edge garden beds so they can’t wash in.
Avoid planting large-rooted trees close to stormwater lines.
Never hose garden waste, concrete washings or paint into a drain.

Fit an Under-Grate Sediment Filter

The most effective step is to catch silt and debris at the inlet before it reaches the pipe. An under-grate sediment filter, also called a stormwater pit insert, sits beneath the grate and lets water through while holding back leaves, litter and soil.

This matters most on building and renovation sites. Exposed soil can send large volumes of sediment into the stormwater system in a single storm, and Australian state environment regulators and local councils require builders to control sediment leaving their sites.

Most pit filters are made from nonwoven geotextile, the same fabric used for erosion control on construction sites. They come as bags or sheets that hang from the underside of the grate, so they can be fitted and emptied without digging. Drain Warden, made by PT Urban Plastik Indonesia, is one example of this type of filter.

What to Look for in a Stormwater Pit Filter

A good pit filter balances two jobs: holding back silt and letting rainwater through fast enough to avoid ponding. These are the properties worth comparing on any product’s technical data sheet. For reference, Drain Warden uses 250 gsm fabric that retains particles larger than 90 microns, with a flow rate of 114 L/m²/s.

Fabric Weight (gsm)

Fabric weight shows how strong and long-lasting the filter is. Heavier fabric generally resists tearing better when it is full of wet sediment.

Apparent Opening Size

The opening size, measured in microns, sets the smallest particles the fabric holds back. Smaller openings catch finer silt but fill faster, so they need emptying more often.

Flow Rate and Permittivity

These figures show how quickly water passes through the fabric. Higher values lower the risk of water ponding around the grate in heavy rain.

UV Resistance

UV resistance shows how well the fabric holds up in sunlight. It matters most for long-term or exposed installations.

Size and Fit

The filter should cover the whole pit opening with an overhang, so water can’t bypass it. Trimmable fabric suits a wider range of pit sizes.

Overflow

In an extreme storm, water needs somewhere to go. Look for built-in overflow openings, or make sure there is a safe overflow path away from buildings.

How to Install an Under-Grate Filter

Installation takes about 10 minutes per pit. You will need gloves, heavy-duty scissors or a utility knife, and cable ties or strong cord. Always unblock and clean the pit first, using the steps above. Steps vary slightly between products, so check the manufacturer’s instructions too.

Lift and clean. Remove the grate and clean the pit’s top lip and opening so the filter sits flat and seals well.
Attach the filter to the grate. Rest the grate on its side and tie the filter securely to its underside with cable ties or cord. If you are also using an oil-absorbent boom to catch fuel and oil runoff, tie it so it hangs in the centre of the filter.
Refit the grate. Lower the grate back into the pit, pulling the fabric edges firmly so the filter fits snugly around the opening with no gaps for water to bypass.
Trim the excess. Cut away surplus fabric, leaving at least a 50 mm overhang around the edges for full coverage.
Check the finish. Make sure the grate sits flush with the surrounding surface so it is not a trip hazard or a hazard for vehicles.

How to Maintain a Pit Filter

A sediment filter only works if it is emptied regularly. A filter packed with silt slows drainage and can cause water to pond around the grate, so build these checks into your routine:

Inspect after every significant rain event, and at least weekly on active building sites.
Empty the filter before silt starts to slow drainage. Lift the grate, remove the trapped sediment and debris, and dispose of it in general waste or as your site’s waste plan requires. Never tip it back into the gutter.
Follow the manufacturer’s guidance on how full the filter can get before emptying.
Replace the filter if the fabric is torn, clogged with fine clay that won’t wash out, or water no longer passes through freely.
On building sites, keep filters in place until the site is stabilised with paving, turf or landscaping, then remove them.

During very heavy storms, water may pond briefly over a filtered grate. Check that water has a safe overflow path away from buildings, especially on low-lying properties.

The Bottom Line

Most blockages near the grate can be cleared in under an hour with a hose and a drain rod, so learning how to unblock stormwater drains is a skill worth having. Call a licensed plumber when the blockage is deep, keeps coming back, or points to damaged pipes. To reduce repeat blockages, keep grates clear of leaves and soil, and consider an under-grate filter on building sites or pits under trees. For more information about Drain Warden please contact: Whatsapp/Mobile Phone: +62 811 9151 338 (Ms. Anna) or Email :info@urbanplastic.id

How to Unblock a Stormwater Drain: Step-by-Step Guide