A blocked kitchen sink is one of the most common household headaches, and a double sink adds a small but important twist to the plunging process. The key difference is that you must seal off the second basin's drain before you plunge, otherwise the pressure you create simply escapes through the other plughole rather than forcing the blockage clear. Done correctly, plunging is a straightforward DIY job that takes just a few minutes.
What You'll Need
Before you start, gather the following:
- A cup plunger (the flat-bottomed style — not a flange/toilet plunger)
- An old cloth, sponge, or rubber stopper to block the second drain
- Rubber gloves
- A bucket and old towels to catch any overflow
- Petroleum jelly (optional, to improve the plunger seal)
You'll find cup plungers at Bunnings or Mitre 10 for a modest cost — as a rough guide, expect to pay somewhere in the range of $10–$30 depending on quality.
Step-by-Step: Plunging a Double Kitchen Sink
Step 1 — Identify the blocked side
Figure out which basin is draining slowly or not at all. This is the side you'll plunge. If both sides are blocked, start with the one that seems worse.
Step 2 — Remove standing water (if needed)
If there's a large amount of standing water, scoop some out into a bucket so the water level sits roughly 5–10 cm deep. You need enough water to cover the plunger cup and create a seal, but not so much that it splashes everywhere when you plunge.
Step 3 — Block the second drain completely
This is the most important step for a double sink. Press a wet cloth firmly into the drain of the unblocked basin, or use a rubber stopper. Hold it in place (or have someone else hold it) throughout the entire plunging process. Without this seal, air and water will simply travel across the shared drain pipe and escape through the open basin, and you'll get no useful pressure at the blockage.
Step 4 — Seat the plunger over the blocked drain
Place the cup plunger squarely over the blocked plughole. For a better seal, you can smear a little petroleum jelly around the rim of the plunger cup. Make sure the cup is fully submerged in water — plungers work on water pressure, not air pressure.
Step 5 — Plunge with firm, steady strokes
Push down slowly to expel air, then use firm, rhythmic up-and-down strokes — around 10–15 pumps in a row. Keep the seal tight throughout. On the final stroke, pull the plunger up sharply to create a strong suction pull. This combination of push and pull pressure is what dislodges most common blockages (grease build-up, food scraps, soap residue).
Step 6 — Test the drain
Remove the plunger and the cloth from the second drain, then run hot water to see if the blocked side is flowing freely. If it drains well, you're done. If it's still slow, repeat the process two or three more times before trying another approach.
Step 7 — Follow up with hot water
Once the drain is clear, run the hot tap for a minute or two to help flush any remaining debris through the pipe.
Why Double Sinks Block More Often
Double kitchen sinks share a single trap and drain line beneath the bench. Grease, food particles, and soap scum accumulate in the shared trap over time. Regular maintenance — pouring boiling water down the drain weekly and avoiding pouring cooking fats down the sink — goes a long way toward preventing repeat blockages.
What NOT to Do
- Don't use chemical drain cleaners immediately — they can damage older pipes and are hazardous to handle. If plunging doesn't work, try a drain snake before reaching for chemicals.
- Don't plunge if you've already poured chemical cleaner down the drain — the splashback can cause serious chemical burns.
- Don't use a toilet (flange) plunger on a sink — the flat cup plunger is the right tool for flat sink drains.
- Don't ignore a recurring blockage — if your sink blocks repeatedly, there may be a deeper issue in the drain line worth investigating.
When to Call a Professional
Plunging is well within DIY territory and is not restricted work under NZ law. However, you should call a licensed drainlayer or plumber if:
- The blockage doesn't clear after several attempts with a plunger and drain snake
- Multiple fixtures in your home are draining slowly at the same time (this suggests a main drain blockage)
- You notice foul smells, gurgling sounds from other drains, or water backing up into other fixtures
- Your pipes are old and you suspect damage or tree root intrusion
Drain clearing that involves working on below-ground drainage or modifying pipework is restricted work under the Plumbers, Gasfitters, and Drainlayers Act 2006 and must be carried out by a licensed professional registered with the Plumbers Gasfitters & Drainlayers Board. For above-trap blockage clearing (like plunging), homeowners can legally do the work themselves.
You can find qualified local drain cleaners and plumbers on tradedirectory.co.nz to get the job sorted quickly if DIY methods aren't cutting it.
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