A slow sink or a gurgling toilet is easy to ignore until water starts backing up. When it does, the first question is usually "how much will this cost to fix?" The honest answer is that it depends on where the blockage is, what's causing it and how the plumber needs to clear it. A blocked kitchen sink and a sewer line full of tree roots are very different jobs.
This guide explains what affects the cost of fixing a blocked drain, who is responsible for which pipes, and how to get quotes you can compare. It applies Australia-wide, but each water utility has its own rules.
Signs you have a blocked drain
Sydney Water's general plumbing information lists common signs of a wastewater blockage:
- sinks, baths or toilets emptying slowly
- a toilet that fills and drains slowly or has overflowed
- gurgling noises from a toilet or floor drain
- wastewater overflowing from the drain (or gully) near your outside tap
The same page says most blockages are caused by tree roots, items that shouldn't be flushed such as wet wipes, fats and oils poured down sinks, and stormwater entering the wastewater system during heavy rain.
Is it your pipe or the utility's?
This matters, because it affects who pays. In general, property owners are responsible for the private pipes on their side of the connection to the water utility's network, and the utility looks after its own pipes. The exact rules vary.
- In Greater Sydney, Sydney Water explains how to tell whether a blockage is in its pipes or yours. Signs it may be in the network include an overflow beyond your property boundary, neighbours with the same problem, or a continuous overflow when you're not using water.
- In Brisbane and nearby areas, Urban Utilities has similar guidance for its customers.
If you think the problem is in the utility's pipes, contact your water utility first. If it's in your private pipes, you'll need a licensed plumber.
What affects the price
Where the blockage is
A blockage close to a single fixture, like a sink trap, is usually quicker to clear than one deep in the main sewer line under the yard or slab.
What's causing it
Hair, soap and food scraps are often cleared quickly. Tree roots, fat build-up and collapsed or cracked pipes take more time and equipment. Root intrusion may come back if the damaged pipe isn't repaired.
The method used
Plumbers have different tools for different blockages:
- Plungers and hand augers for simple, close blockages
- Electric eels or drain machines for tougher blockages and roots
- High-pressure water jetting to clear fat, roots and debris from longer runs
- CCTV drain cameras to find the cause and check the pipe's condition
If the pipe is damaged, repair options can include digging and replacing a section, or trenchless methods such as pipe relining. These are bigger jobs and are usually quoted separately.
Access
An accessible inspection opening makes a big difference. If the plumber can't easily reach the pipe, they may need to remove a fixture or find another access point.
Time of day
Emergency, after-hours, weekend and public holiday call-outs usually cost more than a booked weekday visit. If a toilet is still usable or you can avoid using a fixture safely, booking ahead may save you money.
How to get quotes you can compare
Blocked drains are often priced on the spot, so ask questions before the plumber starts:
- Is there a call-out fee, and what does it cover?
- Is the price hourly or fixed for clearing the blockage?
- Will you use a camera, and is that included?
- If you find a damaged pipe, will you give me a written quote before doing repairs?
- Is GST included?
For non-urgent repairs, such as fixing a cracked pipe after a blockage is cleared, get two or three written quotes for the same scope.
Check the licence
Drainage work generally needs a licensed plumber or drainer, and the rules differ between states. For example, in Queensland the QBCC says plumbing and drainage work of any value needs a QBCC licence. Check your state's official register before work starts. Our guide on how to check a tradie's licence in every state and territory lists where to look.
How to help prevent blockages
- Don't flush wet wipes, sanitary items or paper towels, even if labelled "flushable".
- Scrape food scraps into the bin and let fats cool before binning them, rather than pouring them down the sink.
- Use drain strainers in sinks and showers.
- Think about where you plant trees with aggressive roots in relation to your sewer line.
- Make sure downpipes and stormwater don't run into your sewer.
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Frequently asked questions
Who pays to fix a blocked sewer?
Generally, property owners are responsible for their private pipes and the water utility is responsible for its network. The exact boundary depends on your utility, so check its website.
Can I clear a blocked drain myself?
You can try a plunger on a simple sink or toilet blockage. Avoid harsh chemicals and call a licensed plumber if it doesn't clear or keeps coming back.
What is a drain camera inspection?
A plumber feeds a small camera into the pipe to find the cause and check the pipe's condition. It helps decide whether a repair is needed.
Will tree roots come back after the drain is cleared?
They can, especially if the pipe is cracked. Ask the plumber about repair options once the blockage is cleared.
This guide is general information only, not legal or financial advice. Rules change, so check the official sources linked above for your state.