A blocked drain in a concrete laundry tub is one of the more common household plumbing headaches in New Zealand homes — especially in older properties where concrete tubs are still going strong. The good news is that most blockages are caused by lint, soap scum, or debris and can be cleared yourself with a few simple tools and a bit of patience.
Why Concrete Laundry Tub Drains Block Up
Concrete laundry tubs see a lot of heavy-duty use — washing muddy sports gear, rinsing paint brushes, and handling laundry overflow. Over time, the drain can accumulate:
- Lint and fabric fibres from washing machine discharge
- Soap scum and detergent build-up
- Dirt, sand, and grit from outdoor clothing and equipment
- Hair and other organic matter
- Grease or paint residue if the tub doubles as a utility sink
The drain strainer (the small grate or plug fitting in the tub floor) is your first line of defence, but it can't catch everything.
What You'll Need
| Tool / Product | Where to Find It |
|---|---|
| Rubber plunger | Bunnings or Mitre 10 |
| Drain snake / hand auger | Bunnings or PlaceMakers |
| Enzyme or caustic drain cleaner | Hardware stores or supermarkets |
| Bucket and old towels | At home |
| Rubber gloves and eye protection | Hardware stores |
Step-by-Step: How to Unblock the Drain
1. Remove and Clean the Strainer
Start simple. Lift or unscrew the drain strainer and remove any visible gunk — lint, hair, and debris often collect just below the surface. Rinse the strainer under a tap and replace it. Try running water to see if this alone solves the problem.
2. Try Boiling Water (With Caution)
For soap and grease build-up, carefully pour a kettle of very hot (not necessarily boiling) water slowly down the drain. This can soften and shift fatty deposits. Do this two or three times with a minute between pours. Note: avoid boiling water if your drain connects to PVC pipework, as extreme heat can soften plastic joints over time.
3. Use a Plunger
If hot water doesn't do the trick, a cup-style rubber plunger is your next move. Fill the tub with enough water to cover the plunger cup, place it firmly over the drain opening, and pump vigorously up and down 10–15 times. The pressure change can dislodge the blockage. Repeat a few times if needed.
4. Try a Baking Soda and Vinegar Flush
For a gentler, chemical-free approach, pour half a cup of baking soda down the drain followed by half a cup of white vinegar. Cover the drain and leave for 20–30 minutes, then flush with hot water. This works well on mild organic build-up and is safe for most pipe types.
5. Use a Drain Cleaner Product
If the blockage persists, a commercial drain cleaner may be needed. There are two main types:
- Enzyme-based cleaners — slower acting but gentler on pipes and the environment. Good for regular maintenance.
- Caustic (alkaline) cleaners — faster acting but must be used carefully. Always wear rubber gloves and eye protection, ensure good ventilation, and follow the manufacturer's instructions exactly. Never mix different drain cleaning products together, as this can cause dangerous chemical reactions.
Check the product label to confirm it is suitable for use with your pipe material (PVC, cast iron, or clay).
6. Use a Drain Snake or Hand Auger
If chemical methods haven't worked, a hand-operated drain snake (also called an auger) can physically break up or retrieve the blockage. Feed the cable into the drain, turn the handle to work it through the pipe, and pull back to remove debris. This is particularly effective for solid blockages like accumulated lint or a foreign object.
Preventing Future Blockages
- Fit a lint trap on your washing machine outlet hose — these are inexpensive and widely available at hardware stores.
- Clean the drain strainer weekly if the tub gets heavy use.
- Flush the drain with hot water after each use.
- Run an enzyme drain cleaner through the system monthly as a maintenance measure.
- Avoid rinsing paint, plaster, or cement down the tub — these can set hard inside the pipes.
When to Call a Professional
Some blockages are beyond DIY methods, and there are situations where you should call a licensed drain layer or plumber:
- The blockage keeps returning despite repeated clearing.
- Multiple drains in your home are slow or blocked at the same time (this may indicate a main drain blockage).
- You can hear gurgling from other fixtures when you use the tub.
- There is an unpleasant sewage smell, which could indicate a more serious drainage issue.
- The drain pipe itself appears cracked, corroded, or damaged.
Drainlaying and certain plumbing repairs are restricted work under New Zealand law and must be carried out by a licensed tradesperson registered with the Plumbers, Gasfitters and Drainlayers Board. Attempting restricted work yourself can result in fines and may affect your home insurance.
You can find qualified, local drain cleaners and plumbers on tradedirectory.co.nz.
Safety Note
Always wear gloves and eye protection when using chemical drain cleaners. Never mix products, and keep children and pets away from the area. If you've already used a chemical cleaner and it hasn't worked, tell any tradesperson you call — they'll need to know before working on the drain.
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