A slow or blocked drain and a broken or collapsed pipe can produce very similar symptoms, but the fixes are completely different and so are the costs. Knowing which one you’re dealing with changes your next step significantly. This guide covers the key differences, how to read the signs, and when you need a CCTV inspection to be certain.
The quick answer
A simple blockage (grease, hair, roots, debris) can often be cleared with jetting. A broken, cracked or collapsed pipe needs structural repair, point repair, drain relining or excavation depending on severity. The only way to know for certain which you have is a CCTV drain inspection. The symptoms can overlap, but certain patterns suggest one over the other.
Symptoms that suggest a simple blockage
A blockage, whether caused by grease, roots, hair, scale or a foreign object, typically presents as:
| Symptom | Notes |
|---|---|
| Single fixture slow or blocked | Usually an internal fixture trap or sub-branch issue |
| Recent change (new blockage, not a recurring issue) | Suggests a debris blockage rather than structural failure |
| Clears after high-pressure jetting | A cleared blockage that doesn’t return suggests debris |
| Back-surge only when heavily loaded | Suggests partial blockage that manages low flow |
| No symptoms between blockage events | Pipe is structurally OK between blockage events |
A simple blockage is typically caused by:
- Grease buildup in kitchen drain lines
- Hair and soap scum in bathroom lines
- Tree roots that have grown to a blocking density
- A foreign object (toy, wipe, nappy) lodged in the pipe
In most cases, a blockage can be cleared by hydro jetting. However, if the underlying cause (particularly roots) isn’t addressed, the blockage will recur.
Symptoms that suggest a broken or collapsed pipe
A structurally compromised pipe behaves differently from a simple blockage. Signs that point toward structural failure include:
| Symptom | What it suggests |
|---|---|
| Recurring blockages every 6-18 months | Roots regrowing through open joints, structural issue |
| Multiple fixtures backing up simultaneously | Main drain failure: blockage OR collapse downstream |
| Sewer odour outside but no active blockage | Sewer gas escaping through cracked pipe |
| Wet patch in garden with no leaking fixture | Sewer exfiltrating through crack or hole |
| Sunken or soft area in garden over pipe line | Soil washout caused by exfiltrating pipe |
| Sewage smell inside walls or under floor | Cracked pipe under slab or in sub-floor |
| Cracked concrete near drains with no obvious cause | Soil subsidence from pipe exfiltration |
| Drain never clears fully even after jetting | Collapse or severe offset preventing full bore |
The trickiest overlap: root intrusion
Root intrusion is the case where blocked-drain and broken-pipe symptoms overlap most. Roots enter through a structural defect (joint gap or crack), which is a structural problem, but the symptom they cause (blockage) looks like a simple blockage.
Here’s the key: if you’ve had a drain jetted and the roots were cleared, but the blockage returned within 12-18 months, the pipe has a structural entry point. Clearing the roots again is temporary maintenance. The actual repair is drain relining to seal the entry points.
Signs that make the distinction clearer
Signs pointing strongly toward “broken pipe”
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You can see or smell sewage in the yard, this is exfiltration. The pipe is broken and sewage is escaping. This is an urgent health hazard.
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The drain clears with jetting but another blockage forms in a different location within weeks, suggests the pipe wall is so deteriorated that blockages are forming at multiple defect points.
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The drain cannot be completely cleared despite jetting, if the jetter can’t push through, there may be a collapse reducing the bore to near-zero.
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You have subsidence or a sinkhole in the garden above the drain line, soil washout from a broken pipe creates voids underground that eventually cause surface subsidence.
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The blockage event caused sewage to back up through a ground-level fixture, this indicates the main line is blocked or collapsed far enough downstream that all fixtures are backing up.
Signs pointing strongly toward “simple blockage”
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Only one fixture is affected, usually indicates a local trap or sub-branch blockage.
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The drain cleared completely and you’ve had no issues for years, a structural failure tends to be progressive; recurrence is common.
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The pipe is PVC installed in the last 20 years, PVC is rarely structurally compromised at this age, though blockages are still common.
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The blockage coincides with a specific event, children’s toys flushed, a guest who doesn’t know the rules, a grease-heavy cooking period.
When to get a CCTV drain inspection
In all these cases, book a CCTV inspection:
- Recurring blockages (more than once in 2 years in the same pipe)
- Any symptom that suggests possible pipe damage (odour in yard, wet patch, subsidence)
- Before purchasing an older Central Coast property
- After a major root clearing job, to assess the structural condition of the pipe
- Before planning landscaping or construction that will be over a drain line
A CCTV inspection costs $250, $500 and gives you certainty. Without it, you’re guessing, and the wrong repair choice can cost you thousands more than the inspection would have.
See our CCTV drain inspection explained guide for what the inspection covers.
What each type of problem costs to fix
| Problem type | Typical fix | Typical cost range |
|---|---|---|
| Simple grease/hair blockage | Hydro jet clearing | $200, $400 |
| Root blockage (temporary fix) | Hydro jet + root cutting | $300, $600 |
| Root intrusion with joint gaps (permanent fix) | CCTV + drain relining | $3,800, $9,000 |
| Cracked pipe section | CCTV + point repair or reline | $900, $6,000 |
| Collapsed section | Excavation + replacement + optional reline | $3,000, $15,000+ |
| Foreign object blockage | CCTV + retrieval or flush | $300, $800 |
What happens if you treat a broken pipe as a blockage
The risk of misdiagnosis is real. If you have:
- A collapsed pipe that gets hydro jetted but not repaired, the pipe will block again immediately and further deterioration continues
- A cracked pipe leaking sewage underground, environmental contamination, potential enforcement from Council, and soil washout that worsens over time
- Root intrusion that’s repeatedly cleared without relining, the pipe condition worsens with each root cutting (the cutter can damage fragile older pipe walls)
Getting the diagnosis right the first time saves money, time and stress.
Frequently asked questions
Can I tell from the sound of my drains whether the pipe is broken? Not definitively. Gurgling from multiple fixtures suggests a downstream restriction, which could be blockage or structural failure. Gurgling after rain suggests stormwater infiltration into the sewer, which requires CCTV to confirm.
My drain was cleared 3 months ago and it’s blocked again, is that broken pipe territory? Not necessarily, it depends on what was cleared. If roots were cleared, recurring blockage within 6 months strongly suggests structural entry points that need relining. If grease was cleared and it’s blocked again with grease, it’s a behaviour and maintenance issue.
The plumber says I need relining but I only had one blockage, should I get a second opinion? Yes, if the first contractor couldn’t show you CCTV footage justifying the recommendation. Relining based purely on a blockage history, without CCTV evidence of structural defects, is not appropriate. See our guide to choosing a drain relining contractor.
Is a broken pipe more urgent than a blockage? Generally yes. A blockage is inconvenient; a broken pipe leaking sewage underground is a health hazard and a liability. If you suspect sewage exfiltration, treat it as urgent.
Can a pipe be partially broken and still drain? Yes, very commonly. Cracked pipes, offset joints, and even pipes with significant root intrusion can still drain at reduced capacity. The pipe isn’t “working fine”, it’s draining despite the damage, and the damage is progressing.
Not sure what’s going on with your drains? Book a CCTV inspection for a definitive answer.