Three days after the last decent rain, a bloke in Casula rang me because his back lawn still squelched. Sloping block, a grated stormwater pit in the corner that filled to the brim every time it rained and took a day to go down. His neighbour had told him council would fix it. Council would not. Everything from his gutters to the kerb was his, and the camera showed why: twelve metres of 90mm stormwater pipe packed with silt and a root ball the size of a football at the outlet.
That is a typical blocked stormwater drain, and the answer is usually the same. Clean the pit yourself first. If it still overflows in the next downpour, the pipe leaving it needs a camera and a jet blast, and a crushed or unconnected pipe needs digging. We do roof plumbing and stormwater, no call-out fee, across Liverpool, Fairfield and Macarthur, with our own excavator.
Stormwater drains block with leaves, silt and tree roots, or the old pipe has crushed, collapsed or was never connected to the kerb. Lift the pit grate and scoop it out first. If water still pools or the pit overflows in the next downpour, the line needs a camera and a jet blast, and everything on your side of the kerb is the owner's job, not council's.
What a stormwater drain and a stormwater pit actually do
Sydney homes have two separate drainage systems. The sewer takes the toilets, sinks and showers out to Sydney Water's main. Stormwater is the other one: rain off the roof runs down the downpipes into a buried stormwater pipe, picks up any surface pits along the way, and leaves the block at an approved point of discharge. For most houses that is a kerb outlet, the small rectangular hole cut through the concrete gutter out the front. On the newer estates in Oran Park and Gregory Hills it is often an inter-allotment drain along the back fences.
A stormwater pit is just a box in that line: a grate on top, a sump underneath where silt settles, and an outlet pipe leaving the side. They sit at low points, at the bottom of driveways and wherever the pipe changes direction. They are the part you can see, so they get blamed for everything, but half the time the pit is fine and the pipe leaving it is the problem. The standard residential stormwater pipe is 90mm PVC, the same grey pipe as the downpipes, with 100mm on bigger blocks and the main run to the kerb. Older homes around Fairfield and Cabramatta still have earthenware lines, and those are the ones tree roots love.
Why stormwater drains block
Stormwater has no constant flow to keep itself clean. The pipe sits dry for weeks, then cops a downpour carrying leaves, gumnuts, mulch and roof grit. Anything that settles in a flat section stays there, and a pipe laid with too little fall builds silt into a plug over a few years. Tree roots come in through old earthenware joints and unglued PVC joints, and the silt catches on the root mat. Crushed pipe is the other big one: a driveway poured over an unprotected line, or a car parked on the lawn.
Then there are the older blocks around Austral and Leppington that were never connected to the kerb at all. The downpipes run into a rubble pit that silted up decades ago, so the roof water backs up and spills out at the base of the downpipe. And on plenty of newer builds the downpipe simply stops in the dirt.
Blocked stormwater drains: symptoms, causes and the usual fix
| What you see | Likely cause | Usual fix |
|---|---|---|
| Downpipe overflows at the base | Blocked line downstream, or downpipe not connected | Jet blast the line, or connect it properly |
| Pit fills in rain and takes a day to drain | Silt or roots in the outlet pipe | Clean the pit, jet blast and camera the line |
| Pit overflows even in light rain | Crushed pipe past the pit, or no outlet at all | Camera to locate it, dig and replace |
| Soggy patch of lawn that never dries | Broken pipe leaking underground | Locate, excavate and replace |
| Water under the garage door or into the subfloor | Surface water with no pit or strip drain | Install a pit or channel drain |
What you can safely do yourself
Cleaning a stormwater pit is not licensed work, so start there. Lift the grate, put gloves on, and scoop out the leaves and sludge down to the outlet pipe. Run a hose into the outlet at full pressure. Clean the gutters while you are at it, because the pit only fills with what the roof sends it. A jet nozzle pushed a metre into the pipe can shift a soft leaf plug, and that is about the limit of it.
Do not tip drain cleaner or caustic soda into a stormwater pit. It does nothing to silt or roots, it ends up in the creek, and it burns whoever puts their hands in that pit next, which is usually me. Do not dig along the line with a shovel to find the block, unless you enjoy finding the gas, sewer and NBN by mistake.
How a stormwater plumber clears it
I start with the CCTV drain camera, because guessing is expensive. It goes in through the pit or a downpipe and shows me silt, roots, a crushed section or a pipe that just ends, and its sonde lets me mark on the lawn exactly where the fault is and how deep. Then the jet blaster goes in. High pressure water cuts roots, flushes silt back to the pit, and clears the full bore of the pipe. I have written up how jet blasting works and when it is the right call.
A second camera pass tells us whether the problem is solved or postponed. Cut roots grow back through the same joint, silt settles again in a pipe with no fall, and a crushed pipe stays crushed. Then the conversation is about repair.
Repairing or replacing a stormwater pipe
Stormwater is normally shallow, so replacement is often cheaper and better than relining. I bring the mini excavator, cut out the crushed or rotten section, lay new 90mm or 100mm pipe with proper fall, and put in new pits where they are needed. Under a driveway or path the Grundomat boring tool pushes a new line through without cutting the concrete. For a block that was never connected to the street, the job is a new line to the front boundary and a kerb outlet cut into the gutter. That is work in the road reserve, so it needs council's consent under the Roads Act first, and I organise that. All of it is stormwater plumbing done to AS/NZS 3500.3, the stormwater drainage standard. Done right. Done once.
Who is responsible: you, council or Sydney Water
Everything on your block is yours: gutters, downpipes, stormwater pipes, stormwater pits and the line to the kerb or the easement. Council looks after the street side: the gutter, the street pits and the pipes under the road. Sydney Water does not touch stormwater on private property. Wingecarribee Shire Council's stormwater fact sheet spells it out, and the principle is the same across Liverpool, Camden and Campbelltown: the owner keeps their own drainage working, discharges it to an approved point, and accepts the natural overland flow from uphill without diverting it onto anyone else.
One exception: if a council street pit out the front is blocked and the gutter is backing up onto your driveway, report it to council.
What stormwater drain cleaning costs
Clearing a blocked stormwater drain with the jet blaster sits in the $180 to $450 range on Sydney 2026 price guides, with a call-out fee of $69 to $170 on top. The camera is quoted on inspection and usually bundled with the clear. Digging, new pits, new pipe runs and kerb outlets are quoted on inspection, and what moves the price is depth, length, concrete in the way, the council permit, and how much lawn or driveway has to be put back. You get the price before I start.
A blocked stormwater drain is rarely an after-hours emergency. Unless water is entering the house, wait for business hours and save the emergency rate. Sewage coming up at the gully or in the shower is a different problem: blocked drains, causes and when to call covers it, as does the blocked drains page.
When to call a stormwater drainage plumber
Call when you have cleaned the pit and it still overflows, when a downpipe backs up in every shower of rain, when a patch of lawn stays wet for days, or when cracks are opening in paths and brickwork near a wet area, because moving water undermines footings. And call the day you notice it, not in the middle of the next east coast low when every plumber in Sydney is flat out.
Monarch Civil & Plumbing covers South West Sydney and the Macarthur region from Austral. See the sewer and stormwater drainage page, and if you need a plumber in Casula, a plumber in Oran Park or anywhere in between, ring 0455 222 292 for a straight answer on what it needs.
Related guides: downpipes overflowing and tree roots in drains.
Need it sorted? Ring 0455 222 292 any hour or book online. Monarch Civil & Plumbing does roof plumbing and stormwater, no call-out fee: pits, lines, kerb outlets and absorption trenches, quoted before we start.
Blocked drain in Liverpool, Fairfield or Campbelltown?
The local pages say what is usually wrong in your suburb and what Paul does about it: blocked drains Liverpool, blocked drains Fairfield and blocked drains Campbelltown. Everywhere else within about 20 km of Austral, the blocked drains page covers how a job runs and service areas lists every suburb. No call-out fee anywhere, and the camera goes down before anything is quoted.
Frequently asked
Who is responsible for a blocked stormwater drain in NSW, the owner or council?
On private property it is the owner. Gutters, downpipes, stormwater pipes, stormwater pits and the line out to the kerb or easement are all yours to maintain and repair. Council looks after the street pits, the kerb and gutter and the pipes under the road. Sydney Water does not handle stormwater on private property. If a street pit out the front is blocked and flooding your driveway, report that one to council.
Why does my stormwater pit overflow in heavy rain?
Either the pit itself is full of silt and leaves, or the outlet pipe leaving it cannot take the water fast enough. A pit that fills and drains slowly over a day usually has silt or roots in the outlet pipe. A pit that overflows even in light rain usually has a crushed or collapsed pipe past it, or was never connected to a proper outlet. A camera inspection shows which one you have.
What size is a residential stormwater pipe?
Most house stormwater lines are 90mm PVC, the same grey pipe used for downpipes, and 90mm stormwater pipe is what I lay for standard downpipe runs. Larger properties and the main run from a big pit to the kerb often step up to 100mm. Older homes may still have earthenware pipe, which cracks and lets tree roots in, and that is usually replaced with PVC when it fails.
Can I connect my stormwater to the sewer to get rid of the water?
No. Stormwater and sewer are separate systems in Sydney and connecting roof or surface water into the sewer is not permitted. It overloads the sewer in heavy rain and causes overflows, and Sydney Water can require it to be disconnected. Stormwater has to go to an approved point: the kerb and gutter, an inter-allotment drain or a council easement. If your block has no connection, that is the job to fix.
How much does stormwater drain cleaning cost in Sydney?
Jet blasting a blocked stormwater drain sits around $180 to $450 on Sydney 2026 price guides, with call-out fees of $69 to $170 depending on the plumber and the time of day. A camera inspection is quoted on inspection and often bundled with the clear. Digging out and replacing crushed pipe, installing new pits or cutting a kerb outlet is quoted on inspection, and depth, access, concrete and council permits are what move the price.
How often should stormwater pits be cleaned?
Check them every autumn and after any big storm, and clean them whenever there is more than a few centimetres of silt and leaves in the sump. A pit under a gum tree or at the bottom of a driveway might need doing three or four times a year. It takes ten minutes with gloves and a bucket, and a clean pit is the cheapest stormwater maintenance there is.
Licensed plumber and drainer based in Austral, 13+ years in the trade, working across Liverpool, Fairfield and the Macarthur region. About Paul