Sink Completely Blocked: Causes, Checks & Fixes

Stop using affected fixtures if water or sewage is backing up

Wear gloves, keep children and pets away, and avoid mixing chemical drain cleaners. Do not dismantle traps after chemicals have been poured into the drain. Multiple blocked fixtures usually mean the fault is deeper in the drainage system.

MOST LIKELY CAUSES

Start with these

Trap fully blocked Dense debris can seal the U-bend or bottle trap.

Grease plug Kitchen grease can harden into a complete obstruction.

Foreign object Caps, jewellery or food items may lodge in the waste.

Downstream pipe blockage The trap may be clear while the branch pipe remains blocked.

◫ Symptom variations Match the drainage pattern before clearing. ⌄

Water does not move at all
Plunging causes water in another bowl
Trap refills immediately
Waste backs up into sink
Blockage returns after temporary clearing

✓ Quick checks Work from the fixture towards the main drain. ⌄

Stop using the fixture if the water level is rising.
Check the plughole, strainer, cover or removable trap insert.
Identify whether one fixture or several drains are affected.
Listen for gurgling and check the lowest outside drain for backup.
Use mechanical clearing before harsh chemicals.

If flow returns: run clean water gradually and check joints for leaks.

If backup continues: stop adding water and arrange deeper drain clearing.

1 Step 1 — Remove standing water and debris Use mechanical clearing methods carefully and stop if the blockage is deeper. ⌄

Process

Bail out the sink and clear the strainer or plughole.

Success looks like: The work area is manageable and surface debris is removed.

Escalate when: If water refills, another connected waste may be backing up.

2 Step 2 — Plunge with the overflow sealed Use mechanical clearing methods carefully and stop if the blockage is deeper. ⌄

Process

Use a suitable plunger and block the overflow opening.

Success looks like: The obstruction breaks free.

Escalate when: If not, the trap must be opened.

3 Step 3 — Remove and clean the trap Use mechanical clearing methods carefully and stop if the blockage is deeper. ⌄

Process

Place a bowl underneath and dismantle the trap carefully.

Success looks like: A local blockage is cleared.

Escalate when: If the outlet pipe remains full, use a suitable snake or call a plumber.

⌁ Common causes explained Why wastes slow down or block. ⌄

A sink that will not drain usually has a solid blockage in the plughole, trap, short waste run or shared pipe, often made from grease, food, soap or foreign objects.

A local blockage affects one trap or short branch. Several blocked or gurgling fixtures usually indicate a shared branch, main drain or ventilation problem.

⌘ Advanced diagnostics Plumber and drainage-contractor checks. ⌄

Snake the branch waste safely.
Inspect for poor pipe fall or collapsed flexible waste.
Check shared appliance and double-bowl connections.
Clear grease mechanically rather than pushing it farther.
Pressure-test joints after reassembly.

▣ Parts that may need replacing Common components linked to this fault. ⌄

Trap washers
Replacement trap
Waste pipe or fittings
Strainer assembly
Pipe clips

! When to call a plumber or drainage contractor Conditions that should end basic clearing. ⌄

Several drains or toilets are affected.
Sewage is backing up or overflowing.
The blockage returns repeatedly.
A foreign object is stuck in a toilet or pipe.
Drain rods meet solid resistance or become stuck.
A collapsed drain, roots or poor pipe fall is suspected.

? Frequently asked questions Common questions about blocked drains. ⌄

Should I use chemical drain cleaner?

Mechanical cleaning is usually safer and more effective. Chemicals can damage some fittings and create a hazard when traps are opened.

Why do several drains gurgle together?

They may share a partially blocked branch or main drain, causing air to move through nearby traps.

Why does the blockage keep returning?

The pipe may still be partially restricted, poorly laid, damaged or affected by roots or heavy deposits.