A gurgling laundry floor drain is almost always caused by one of two things: a partial blockage somewhere in the drain line, or a dry trap that's letting sewer gases bubble back up through the water seal. The good news is that many cases can be sorted with basic DIY steps — but some situations do require a licensed plumber.
What's Causing the Gurgling?
Before you grab a plunger, it helps to understand what's going on. Your floor drain has a P-trap (a U-shaped bend that holds water) designed to block sewer gases from entering your home. Gurgling happens when:
- Air is being sucked past the trap due to a downstream blockage creating negative pressure
- The trap has dried out from infrequent use, allowing gases to pass freely
- Lint, soap scum, or debris has partially blocked the drain itself
- A venting issue is causing air pressure problems in the drain system
Under the NZ Building Code, sanitary drainage systems (covered by clause G13) must be properly vented to prevent exactly this kind of pressure problem. If venting is the root cause, that's a job for a professional.
Tools and Materials You'll Need
Step-by-Step: Clearing a Blocked Floor Drain
1. Check and Refill a Dry Trap
If your laundry floor drain isn't used often, the trap water may have simply evaporated. Pour about two litres of water slowly down the drain. If the gurgling stops and there's no bad smell, a dry trap was likely the culprit. Adding a small amount of cooking oil on top of the water can slow future evaporation.
2. Remove the Drain Grate and Inspect
Use a screwdriver to lift or unscrew the drain grate. Shine a torch into the drain and look for visible lint, hair, or debris sitting just below the surface. Pull out any gunk by hand (gloves on!) or with needle-nose pliers.
3. Plunge the Drain
Cover the drain opening with a cup plunger, ensuring a good seal. Push down firmly and pull up sharply — repeat 10–15 times. This can dislodge a partial blockage further down the pipe. Run water to test.
4. Use a Drain Snake
If plunging doesn't work, feed a flexible drain snake (also called an auger) into the drain. Rotate it as you push it in to break up or hook onto blockages. Most household blockages sit within the first metre or two of pipe. Pull the snake out carefully and dispose of any debris.
5. Try a Baking Soda and Vinegar Flush
For mild build-up, pour half a cup of baking soda followed by half a cup of white vinegar down the drain. Let it fizz for 15–20 minutes, then flush with a full kettle of hot (not boiling) water. This can help dissolve soap scum and light grease.
Avoid harsh chemical drain cleaners where possible — they can damage older pipes and are hazardous to handle. WorkSafe NZ recommends safe chemical handling at all times.
6. Check Other Fixtures
If your toilet, shower, or washing machine also gurgles or drains slowly at the same time, the blockage is likely further down the shared drain line — beyond DIY reach.
Preventing Future Blockages
- Install a lint trap on your washing machine outlet hose
- Clean the drain grate monthly
- Pour a litre of water down infrequently used drains every few weeks to keep the trap full
- Avoid washing pet hair or large amounts of debris into the drain
Healthy Homes and Rental Properties
If you're a landlord, note that Tenancy Services Healthy Homes standards require rental properties to be in a reasonable state of repair, which includes functional drainage. Persistent gurgling or drainage issues should be addressed promptly.
When to Call a Professional
Call a licensed plumber if:
- DIY steps haven't resolved the gurgling after a couple of attempts
- Multiple fixtures are gurgling or draining slowly simultaneously
- You can smell sewage consistently — this may indicate a broken or blocked drain or a venting fault
- Water is backing up out of the floor drain
- You suspect the blockage is in the main drain line or underground pipes
Drain repairs beyond simple clearing — especially any work on sanitary drain lines, venting, or underground pipes — is restricted plumbing work under the Plumbers, Gasfitters and Drainlayers Board (PGDB). This work must be carried out by a licensed plumber or drainlayer. Attempting it yourself is illegal and could void your home insurance.
You can find qualified, local plumbers on tradedirectory.co.nz — look for someone with current PGDB registration.
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