Home›Blog›Why Does My Drain Keep Blocking?

You cleared the drain last month — maybe you paid a plumber to do it — and now it's blocked again. Same sink, same shower, same spot in the yard. It's one of the most frustrating calls I get across Melbourne's east, and I'll tell you straight: a drain that keeps blocking isn't bad luck. It's a signal. Something inside that pipe is catching debris every time water runs past, and until that something is found and fixed, it will keep blocking no matter how many times it's cleared.

The good news is that the cause is almost always identifiable, and once you know what it is, the fix is usually permanent. This guide walks through the five real reasons drains keep re-blocking, why a quick cable clear so often fails, and how a proper diagnosis puts an end to it for good.

Clearing a Drain vs Fixing a Drain

Here's the distinction that matters most. Clearing a drain means shifting whatever is blocking the flow right now — a plunge, an electric eel or a cable that punches a hole through the blockage so water runs again. Fixing a drain means dealing with the reason the debris collected there in the first place.

A cheap clear treats the symptom. If roots, a sagging pipe or a cracked section caused the blockage, that fault is still sitting there after the plumber drives off — quietly gathering the next lot of grease, wet wipes and sediment until it chokes up again. That's why the same drain blocks over and over: it was cleared, but never actually fixed.

"If a drain blocks in the same spot twice, the blockage was never the real problem. The pipe is trying to tell you something — and the only way to hear it is to put a camera down and look."

The 5 Real Causes of a Recurring Blocked Drain

1. Tree roots in the line

This is Melbourne's number one cause of recurring drain trouble, hands down — especially in the established suburbs around the Ranges and Yarra Valley where mature gums, oaks and liquidambars grow right over old clay pipework. Roots hunt for the moisture and nutrients inside your drain and slip in through the tiniest crack or loose joint. Once inside, they fan out into a fine mesh that catches everything flowing past. Cut them out and the line runs clear, but roots regrow, so the blockage comes back on a cycle of one to three years unless the pipe itself is sealed. I cover this in depth in our guide to tree roots in drains.

2. A belly (sag) in the pipe

Melbourne's reactive clay soils swell in the wet and shrink in the dry, and over the years that movement pushes and pulls at underground pipes. A section can drop into a low point — a "belly" — where water no longer runs straight through but pools instead. Every time you drain, solids settle in that dip rather than being carried away, building up until they choke the line. A belly blocks in exactly the same place every time, and no amount of snaking fixes the sag itself.

3. Grease and fat build-up

The classic kitchen-sink offender. Cooking fats and oils go down warm and liquid, then cool and harden inside the pipe, coating the walls with a sticky layer that grabs food scraps and coffee grounds. It narrows the pipe a little more with every wash-up until water barely trickles through. If your kitchen drain is the one that keeps slowing and blocking, grease is almost certainly the reason — and pouring boiling water or supermarket cleaner down it only shifts the surface.

4. A cracked or collapsed section of pipe

Old earthenware and clay pipes crack with age, ground movement and root pressure. A broken pipe has rough, jagged edges inside that snag debris, and a partially collapsed section physically narrows the channel. Both cause blockages that return fast and get worse over time. This is the cause you can't fix with any kind of clearing — the pipe is damaged, and it needs to be repaired.

5. Wet wipes and foreign objects

So-called "flushable" wipes don't break down like toilet paper; they snag on any rough spot, root or joint and knit together into a solid mass. Add sanitary products, cotton buds and the odd kid's toy, and you've got a blockage that reforms around the same catch point again and again. If the recurring block is in a toilet line, this is a prime suspect.

Why the Cheap Drain Snake Keeps Failing

An electric eel or hand cable is a useful tool, and for a one-off soft blockage it does the job. The problem is what it doesn't do. A cable bores a hole through the middle of a blockage so water flows again, but it leaves the grease coating on the pipe walls, it can't rebuild a bellied or cracked pipe, and it barely touches a dense root mass — it just trims the tips. Within days or weeks the pipe re-chokes, and you're back where you started, often paying a second call-out fee for the same drain.

One thing to avoid entirely: supermarket chemical drain cleaners. They rarely clear a real blockage, they do nothing to roots or a damaged pipe, and the caustic chemicals sit against older pipework and corrode it — turning a repair into a replacement.

How Water Serpent Finds the Real Cause

The difference between a guess and a permanent fix is being able to see inside the pipe. On every recurring-blockage callout I run a CCTV drain camera down the line first, so we both watch the live footage and know exactly what we're dealing with — roots, a belly, grease, a cracked section — and precisely where it is. No guessing, no clearing the wrong thing, no spending money on a fix that won't hold.

The camera also gives you something a snake never can: proof. You see the actual fault on screen, you know why the drain kept blocking, and you get a repair matched to the real cause instead of a temporary patch. If you want to understand the process in full, our CCTV drain inspection guide walks through what to expect.

The Permanent Fixes — Matched to the Cause

Once the camera shows what's going on, the repair follows the cause:

  • Grease, sediment and roots — a 5000 PSI hydro-jet scours the pipe back to its full diameter, stripping the grease coating off the walls and cutting roots back to the pipe surface. It's a genuine clean, not a hole punched through the middle, so the pipe runs like new.
  • A cracked, root-invaded or bellied pipe — pipe relining rebuilds the pipe from the inside. A resin liner is set inside the old pipe to form a smooth, seamless, jointless new pipe wall that roots can't penetrate and debris can't catch on — all without digging up your garden, driveway or slab.
  • A badly collapsed pipe — occasionally a section is too far gone to reline and needs excavation and replacement. The CCTV footage tells us upfront if that's the case, so there are no surprises.

For a full breakdown of what these repairs typically cost in Melbourne, see our blocked drain cost guide. Every quote comes as an upfront price before any work starts, so you know the number before you commit.

When to Stop Clearing and Get It Diagnosed

Call for a camera inspection rather than another clear if you notice any of these:

  • The same drain blocks more than twice in a year
  • It re-blocks within weeks of being cleared
  • More than one fixture is slow or gurgling — a sign it's the main line (see our post on why your drain gurgles)
  • A sewage or rotten-egg smell from the drains or yard
  • Damp patches, sinkholes or unusually green grass along the pipe run — a classic sign of a cracked, leaking pipe

Every one of these points to a fault that clearing won't fix — and the longer it's left, the more the pipe deteriorates and the pricier the repair. If it's already backing up, our emergency plumber service runs same-day across Melbourne's east.

Where I Work

I'm based in Kalorama and cover the Ranges and eastern corridor personally — Lilydale, Mooroolbark, Ferntree Gully, Belgrave, Olinda and the surrounding suburbs. These older, leafy areas are exactly where clay pipes and mature trees combine to cause the recurring blockages this guide is all about. Every job is done by me — 20+ years on the tools, CCTV footage shown to you on the day, and an upfront price before any work begins.

Frequently Asked Questions

When a drain blocks in the same place again and again, it's almost never bad luck — something at that spot is catching debris. The usual culprits are tree roots that have grown in through a cracked joint, a belly (sag) in the pipe where water and waste pool, or a broken section of pipe with a rough edge. A cable or snake pushes past it and clears the flow for a while, but the underlying fault is still there, so it blocks again. The only way to know for sure is a CCTV camera down the line to see the exact cause.

If a drain was cleared and blocked again within weeks, the first clear treated the symptom, not the cause. An electric eel or plunge shifts whatever is blocking the flow right now, but if roots, a pipe belly or a cracked section caused it, that fault keeps collecting debris. A proper fix means diagnosing the cause on camera first, then matching the repair to it — hydro-jetting for grease and roots, or pipe relining for a damaged pipe — so it doesn't come straight back.

Yes — tree roots are the number one cause of recurring blocked drains across Melbourne's east, especially in older suburbs with clay pipes. Roots seek out the moisture in your drain and grow in through hairline cracks and joints, forming a mesh that snags everything flowing past. Cutting them clears the line, but they regrow, so blockages return every one to three years unless the pipe itself is sealed with relining.

You stop a recurring blockage by fixing what's causing it, not just clearing it. That starts with a CCTV inspection to identify the exact fault, then the right repair: a high-pressure hydro-jet to scour grease and cut roots back to the pipe wall, or pipe relining to rebuild a cracked, root-invaded or bellied section from the inside without digging. Once the pipe is smooth and sealed again, the drain stops re-blocking.

Drain Keeps Blocking in Melbourne's East?

Stop paying to clear the same drain twice. Call Jack direct on 0425 226 636 for a same-day diagnosis. I'll talk it through over the phone first, and if it needs a visit you'll get a CCTV camera down the line, the real cause shown to you on screen, and an upfront price before any work starts. Same-day service across Lilydale, Ferntree Gully, Mooroolbark and all of Melbourne's outer east.