A slow-draining bathtub is almost always caused by a build-up of hair, soap scum, and body oils in or just below the drain cover — and in most cases you can clear it yourself without reaching for a bottle of caustic drain cleaner. Here are the most effective chemical-free methods, from the simplest to the more involved.
Why Avoid Chemical Drain Cleaners?
Harsh chemical drain cleaners (such as those containing caustic soda or sulphuric acid) can damage older PVC or chrome fittings, are hazardous to handle, and can harm the environment when they enter the wastewater system. They're also often ineffective against solid hair blockages. Mechanical methods are safer, cheaper in the long run, and usually just as effective.
Step 1 — Remove and Clean the Drain Cover
Start with the obvious: remove the drain strainer or cover. Most bathtub drain covers either unscrew with a flat-head screwdriver or simply lift out. Once removed, use an old toothbrush or a pair of needle-nose pliers to pull out any visible hair and soap build-up. You'll often find a surprisingly large clump sitting just below the cover — removing it can restore full drainage immediately.
Rinse the cover clean and replace it. Run the tap and check whether the drain is flowing freely.
Step 2 — Use a Drain Hook or Hair Snake
If clearing the cover doesn't solve the problem, the blockage is likely sitting a little further down the pipe. A drain hook (sometimes called a hair clog remover or drain snake) is a long, flexible plastic strip with barbs along the edge — available at Bunnings or Mitre 10 for just a few dollars.
- Insert the hook into the drain opening.
- Rotate and push it gently down the pipe.
- Pull it back slowly — the barbs will grab hair and debris.
- Repeat two or three times, removing the gunk each time.
- Flush with hot (not boiling) water.
This is the single most effective DIY method for bathtub blockages.
Step 3 — Boiling Water and Baking Soda & Vinegar Flush
For soap scum build-up (rather than a solid hair clog), a hot water flush combined with baking soda and white vinegar can help break down greasy residue:
- Pour about half a cup of baking soda directly into the drain.
- Follow with half a cup of white vinegar.
- Cover the drain opening and leave for 15–20 minutes — the fizzing action helps loosen soap deposits.
- Flush with the hottest tap water you can run (avoid boiling water in PVC pipes, as it can soften joints).
This method works best as a maintenance flush rather than for a severe blockage.
Step 4 — Use a Plunger
A cup plunger (the standard rubber dome type) can dislodge blockages that are further down the drain:
- Remove the drain cover if possible.
- Add enough water to the tub to cover the plunger cup.
- Place the plunger firmly over the drain opening to create a seal.
- Push and pull with firm, steady strokes for 20–30 seconds.
- Remove the plunger and check whether water drains freely.
If your bathtub has an overflow plate (a small cover near the top of the tub wall), block it with a wet cloth before plunging — this ensures the suction goes down the drain rather than escaping through the overflow.
Step 5 — Check the Overflow Assembly
Some older bathtubs have a trip-lever or pop-up stopper mechanism connected to the overflow plate. Hair and debris can accumulate on the linkage rod inside the overflow pipe. Unscrew the overflow plate, carefully pull out the linkage, clean off any build-up, and reinsert it. This is a common cause of slow drainage that's easy to overlook.
Preventing Future Blockages
A little maintenance goes a long way:
- Fit a hair catcher over the drain — inexpensive mesh or silicone strainers are available at most hardware stores.
- Do a monthly baking soda and vinegar flush to keep soap scum from building up.
- Clear the drain cover of hair after every shower or bath.
| Method | Best For | Difficulty | Cost |
|---|---|---|---|
| Remove & clean cover | Surface hair clogs | Easy | Free |
| Drain hook/hair snake | Hair clogs below cover | Easy | Low |
| Baking soda & vinegar | Soap scum build-up | Easy | Very low |
| Cup plunger | Mid-pipe blockages | Moderate | Low |
| Overflow assembly clean | Trip-lever tubs | Moderate | Free |
When to Call a Professional
If you've worked through all the steps above and the drain is still slow — or if multiple drains in your home are slow at the same time — the blockage may be in the main drain line rather than the bathtub branch. This is beyond DIY territory.
Under the Plumbers, Gasfitters, and Drainlayers Act 2006, certain drainlaying work is restricted and must be carried out by a licensed tradesperson. Clearing a blockage in your internal branch drain is generally fine for a homeowner, but work on the main drain, any buried pipework, or connections to the public sewer must be done by a licensed drainlayer or plumber. If in doubt, check with your local council or the PGDB.
A qualified drain cleaner or plumber can use a CCTV drain camera to locate the exact blockage and a hydro-jet to clear it thoroughly. You can find licensed local drain cleaners and plumbers on tradedirectory.co.nz.
Safety note: Always wash your hands thoroughly after handling drain debris, and wear rubber gloves — drain build-up can harbour bacteria.
Master Plumbers
Certifying Plumber
SiteWise
