How to Unblock a Drain: Sink, Shower and Outside, and When DIY Makes It Worse
One slow fixture is usually a local blockage you can clear yourself: hair in the shower waste, grease in the kitchen trap, leaves on the outside grate. Two or more drains backing up at once is the sewer line, and nothing you pour in will reach it. Here is the fix for each drain, the home remedies that work, the ones that damage pipes, and the point where the right move is to stop.
Chemical drain cleaners, coke and boiling water do not clear real blockages and two of them damage pipes. A plunger, a hair hook, a cleaned trap and hot soapy water handle the local ones. For anything in the line, Mr Splash clears it with a drain machine or jetter, cameras the pipe to find the cause, and quotes the fix as one fixed price, GST included.
Which Drain Is Blocked Tells You Where the Blockage Is
Before touching anything, run the other taps. The pattern of what drains and what does not is the whole diagnosis.
One Fixture Slow or Blocked
The shower alone, or the kitchen sink alone. The blockage is in that fixture's waste or trap, within a metre of the plughole. This is the one you can usually clear yourself.
Two Fixtures in the Same Room
Basin and shower both slow. The blockage is in the branch line they share, past the traps. A plunger sometimes moves it; a drain machine reaches it properly.
Everything Backing Up, or the Lowest Drain Overflowing
Toilet gurgles when the shower runs, the floor waste or the outside gully overflows, water rises in the lowest drain when anything is used. That is the main sewer line. Stop using water and call: nothing from a supermarket reaches it.
Outside Only
A gully or grate outside overflowing in rain is stormwater, usually leaves, silt or roots at the pit. A sewer gully overflowing without rain is the sewer line.
How to Unblock a Shower Drain
- Lift the grate and pull out whatever is sitting in the waste. Most shower blockages are hair bound with soap within the first few centimetres.
- Use a hair hook or a zip tool, the cheap plastic strip with barbs from any hardware store, fed down the waste and pulled back up. Repeat until it comes up clean. A straightened coat hanger with a small hook does the same job.
- Plunge if it is still slow, with enough water in the base to cover the cup, a dozen firm push-pulls with the seal held.
- Finish with hot tap water and dishwashing liquid to move the remaining soap scum. Not boiling water: it can damage PVC joints and seals.
- Fit a hair catcher over the waste afterwards. It is the one thing that stops the next one.
How to Unblock a Kitchen or Bathroom Sink
- Plunge first, with the overflow hole covered with a wet cloth so the pressure goes down the pipe, not out the overflow. A dozen push-pulls with the cup sealed over the plughole.
- Clean the trap. Put a bucket under the U-bend, unscrew the two collars by hand, and tip out what is inside. Most kitchen blockages are grease and food in the trap; most bathroom basin blockages are hair and toothpaste. Rinse it, refit it, run the tap and check the collars for drips.
- Hot water and dishwashing liquid down the plughole after the trap is back on, to move the grease film further down the branch. Hot tap water, not boiling.
- A small drain snake through the trap outlet reaches a blockage a metre or two into the branch line. Feed it gently; forcing it can punch through an old pipe.
- Still blocked with the trap clean? The blockage is in the branch or the line, and the next tool is a drain machine.
How to Unblock an Outside Drain
Stormwater grates and pits block with leaves, silt and lawn clippings, and the fix is manual: lift the grate, clear the pit by hand or with a small shovel, and hose the outlet to check it runs. If water still backs up with the pit clear, the stormwater line is blocked further down, usually with roots or a collapsed section, and it needs a jetter.
The sewer gully, the grated bowl in the yard with a plastic or concrete surround, is different. It is the overflow point for the house sewer, designed to spill outside rather than inside. If it is overflowing without rain, the sewer line is blocked downstream of it, and that is the moment to stop using water in the house and call. Do not lift the gully grate and try to clear the sewer from there; it is the wrong access and it is raw sewage.
Tree roots are the cause of most repeat outside blockages in Sydney. They enter at joints and cracks, and a jetter cuts them back, but a camera is what tells you whether the pipe needs relining or replacing rather than clearing again next winter. The blocked drains page covers the equipment and the blocked drain cost guide the market ranges.
Home Remedies: What Works and What Makes It Worse
Most of what is passed around about drains is wrong, and some of it damages the pipes or endangers the plumber who comes next.
Works: Hot Soapy Water
Dishwashing liquid followed by hot tap water dissolves and moves grease and soap scum. It will not shift hair, wipes or roots, but for a slow kitchen sink it is the first thing to try.
Works: Pulling, Not Pouring
A hair hook, a cleaned trap, a plunger, a small snake. Every blockage that clears at home clears because something is removed or pushed through, not dissolved.
Limited: Baking Soda and Vinegar
The fizz can loosen a light film in a slow drain. It does nothing for a real blockage, and it is harmless, which is the best that can be said for it.
Does Not Work: Coke
Cola is a weak acid and mostly sugar. It does not dissolve hair, grease or roots, and the sugar feeds the slime that lines a slow drain. It is a myth that never dies.
Makes It Worse: Chemical Drain Cleaners
Caustic and acid cleaners rarely reach a blockage, they corrode old pipes and damage seals, they generate heat that can soften PVC, and they sit in the pipe as a hazard for whoever opens it next. Mixing products can release toxic gas.
Makes It Worse: Boiling Water and Brute Force
Boiling water can damage PVC joints and seals. Forcing a snake or a high-pressure hose from a hardware store through an old drain can punch through the pipe, turning a blockage into an excavation.
When to Stop and Call a Plumber
More Than One Drain Is Blocked
That is the sewer line, past every trap. A drain machine or jetter and a camera are the only things that reach it.
Sewage Is Coming Up
The gully, the floor waste or the shower backing up with sewage is a stop-using-water situation, and after hours it is a genuine emergency.
It Keeps Coming Back
A drain that blocks every month has a cause: roots, a broken joint, a belly in the pipe, or a build-up the plunger only dents. A camera finds it once.
You Have Used a Chemical
Tell the plumber. A pipe with caustic cleaner sitting in it is opened differently, and it is not safe to jet without knowing.
The Trap Is Clean and It Is Still Blocked
The blockage is beyond what a home snake reaches. The machine is the next step, not more force.
Old Pipes, Old House
Earthenware and galvanised drains in older Sydney suburbs crack and collapse. A camera inspection before any more clearing is the cheap decision.
Blocked Drain Questions, Answered
How do you unblock a drain yourself?
Work out which drain first. One slow fixture is local: pull the hair from a shower waste with a hook, clean the trap under a sink, clear the grate on an outside pit, then plunge and finish with hot soapy water. If more than one drain is backing up, the blockage is in the sewer line and needs a drain machine or jetter.
Does coke unblock drains?
No. Cola is a weak acid and mostly sugar; it does not dissolve hair, grease or roots, and the sugar feeds the slime in a slow drain. Pulling the blockage out or pushing it through with a plunger or snake is what works.
Do chemical drain cleaners work?
Rarely, and they cause damage: they corrode old pipes, damage seals, can soften PVC with the heat they generate, and leave a hazard in the pipe for the plumber who opens it. If you have used one, say so before anyone works on the drain.
Can I pour boiling water down a blocked drain?
Hot tap water with dishwashing liquid is safe and moves grease. Boiling water can damage PVC joints and seals, so keep it below boiling.
Why does my drain keep blocking?
A repeat blockage has a cause the clearing does not fix: tree roots at a joint, a cracked or collapsed section, a belly where the pipe has sagged, or a build-up of wipes and grease. A camera inspection shows which, and whether the answer is clearing, relining or replacement.
What does it mean when the toilet gurgles when the shower drains?
Air is being pushed back through a shared line that is partly blocked. It is one of the clearest signs the blockage is in the sewer line rather than a single fixture, and the point to stop using water and call.
How much does it cost to unblock a drain in Sydney?
It depends on where the blockage is and whether a camera and jetter are needed. The blocked drain cost guide on this site lists current Sydney market ranges with sources and dates. Mr Splash quotes the job as one fixed price, GST included, after seeing what is causing it.
Related: Blocked drains · Blocked sewers · Blocked drain cost · How to unblock a toilet · Is pipe relining worth it
