Every blocked drain is one of two problems: a local clog in a single fixture, or a blockage in the main line that serves the whole house. The first is often a DIY fix. The second never is, and recognising the difference quickly saves both money and mess.
This guide walks through diagnosis, the fixes that genuinely work, the ones that make things worse, and what professional clearing costs.
Local clog or main line? A 30-second diagnosis
If one sink drains slowly and everything else works, the blockage is local to that fixture: hair, soap scum or food solids in the trap or branch line.
If more than one fixture is affected, water gurgles in one drain when another is used, or the lowest drain in the house (usually a shower or the outdoor gully trap) backs up, the blockage is in the main line. Stop running water and call a plumber; everything you flush from this point comes up somewhere you do not want it.
DIY fixes that actually work
For a local clog, work through these in order before spending anything:
- Remove and clean the pop-up waste or strainer; a surprising share of bathroom clogs live in the first 10 centimetres
- Plunge with a proper seal: block the overflow with a wet cloth and give it 15 to 20 firm strokes
- Unscrew the S-trap or P-trap under the sink with a bucket underneath and clear it by hand
- A hand-crank drain snake from the hardware store handles most hair clogs in bathroom wastes
- Boiling water helps grease clogs in metal pipes; use hot tap water only for PVC
What to skip: chemical drain cleaners
Caustic supermarket drain cleaners rarely clear a real blockage. They generate heat that can soften PVC, they turn the standing water above the clog into a chemical hazard for whoever eventually clears it, and plumbers legitimately charge more when they discover the pipe is full of caustic soup.
If a plunger and a trap clean have not fixed it, the honest next step is mechanical clearing, not a stronger chemical.
What a plumber will do, and what it costs
For main line blockages plumbers bring two tools. An electric eel (drain machine) cuts through blockages mechanically and suits most jobs. A high-pressure water jetter scours the full pipe diameter and is the better tool for grease and heavily rooted lines.
Straightforward machine clearing typically costs $200 to $500. A CCTV camera inspection, usually $250 to $500 standalone and often discounted with a clear, shows what caused the blockage and whether the pipe itself is damaged. If roots or a collapsed section are found, relining or excavation is a separate, larger conversation, and you should get the camera footage on file before agreeing to anything.
Stopping it happening again
Recurring blockages are a symptom, not bad luck. Tree roots re-enter through the same joint every year or two; grease rebuilds at the same low spot. If you are paying to clear the same drain repeatedly, a camera inspection to find the root cause is cheaper within two years than the standing appointment.
Day to day: keep fats and oils out of the kitchen sink (jar in the fridge, then the bin), fit hair strainers in showers, and flush nothing but paper. Wet wipes labelled flushable are the single biggest cause of avoidable sewer blockages in Australian homes.
Frequently asked questions
Who pays when the blockage is in the council sewer?+
If the blockage is in the utility's main rather than your private drain, the water authority clears it at no cost to you. Your plumber can usually tell from where the blockage sits relative to the connection point and will advise you to call the utility if it is on their side.
How do tree roots get into sewer pipes?+
Roots follow moisture to tiny leaks at pipe joints, then grow through the gap and mat into a net that catches everything. Older earthenware pipes with cement joints are most vulnerable. Cutting the roots restores flow, but they regrow; relining the pipe seals the entry point permanently.
What does drain relining cost compared to digging?+
Relining typically costs $500 to $1,000 per metre and avoids destroying paving, gardens and driveways, which is where excavation costs blow out. For short damaged sections under expensive surfaces, relining usually wins. Get quotes for both approaches and ask to see the camera footage that justifies either.