Why Is My Drain Smelly?

A close-up of a drain in the bathroom

There are a few reasons you might have a smelly drain. You may not notice anything is wrong until one day you arrive home and there's a very unpleasant smell wafting in from your kitchen or bathroom or outside.

A few things, including drainage issues, can cause any smelly regions in the wet areas of your home.

  • Sewer line
  • Fixture trap
  • Incorrect plumbing
  • Organic build-up

Let's take a look at one of the easier-to-diagnose issues first.

Organic Build-up

Over time, blockages develop from food scraps, hair, soap residue, oils/fats, and other matter washing down the drain.

A good investment would be purchasing a strainer for each sink, basin, and shower drain. This filter will help catch any debris, food, vegetable peelings, fluff, or loose hair before it's washed into the drain, leading to organic build-up and, ultimately, a blockage.

Kitchen sink filter with organic food scrap build-up

How can I fix this?

If you have a smelly or slow-flowing shower drain, see if you can pull out any loose/tangled hair before it becomes a problem.

If it's impossible to reach and remove any knotted hair from your drain, you can try a home remedy to assist with moving the issue along. Firstly, try running hot water down the drain. You can also try a mix of vinegar and bi-carb soda with hot water. This mixture may be enough to soften and loosen any build-up, allowing the water to flow freely again. This same solution may also be helpful in your kitchen and laundry sink drains.

Basic Home Remedy Recipe

  • ½ cup bi-carb soda
  • ½ cup white vinegar
  • Put bi-carb soda down the affected drain
  • Follow with the vinegar
  • Fit the plug over the drain
  • Leave the mix to sit in the drain for 30-60 mins
  • Run hot water down the drain to finish off

You might need to repeat the recipe several times for stubborn, slow-flowing drains. If the issue remains, pick up the phone and call us, Expert Plumbing & Gas Services – save our number to your phone. The problem may be more significant than your DIY skillset. Do not attempt anything more than the above, or you may do more harm than good.

Fixture trap for a sink

Fixture Trap

You may also know it as a P-trap or the U-bend. If you look under your sink, you will see the pipework for drainage. The U-shaped bend in the pipe you can see is the fixture trap or P-trap. This pipe holds water to "trap" or keep any gases from your sewer pipes escaping back up the drain and into your home. When running water through these drains, you continually refresh the water in the U-Bend, flushing out the old water and filling it with fresh, clean water.

Why does it smell, and is this something I can fix?

If you have a second bathroom or shower or a connection that you rarely use, the water in the fixture trap might evaporate or dry out over time, and you may begin to notice a slight odour coming from that area in the house. You will avoid this issue if you run the water through your connections regularly.

Incorrect Plumbing

Any number of things could cause a smelly drain, and a few possibilities are listed below

  • Missing fixture trap
  • Leaking drains
  • Incorrect gradient on drains
  • Poor ventilation in drains

If you have a look in the cupboard under your sink and it is missing the P-trap/U-bend section, this could also be an issue. If you have plumbing incorrectly installed or have a mate come over to give you a hand over the weekend, you may have a straight piece of pipe or the fixture arm without the all-important fixture trap. It could also be that the drain doesn't have the correct gradient/fall, causing a problem. Issues to do with incorrect pipe fixtures or gradients will need fixing.

Incorrect plumbing set-up under a sink

All drains can develop a leak. It could be that the smell is not coming from the drain itself but rather from a leak into the cupboard from a leaky tap or a leaky drainpipe connection. The damp construction material of your vanity or cabinets could cause a musty smell. Attend to all leaks immediately to avoid further damage or costly replacements.

When a licenced plumber installs your drainage, they check levels to ensure the correct gradient will give you good flow through the pipe. If installed with either too great or too little angle or, worse still – no gradient at all, this can cause issues with your drainage.

Ventilation is also essential to the overall health of your drainage. Without the correct ventilation, your drainage may become smelly and need attention.

Sewer Repairs Leak Detection under concrete slab

Sewer Line

It can be rather unpleasant when you have smells coming from the sewer line. You may have a blocked sewer if you notice gurgling in the shower, basin or sink drains when running water in another area or flushing the toilet. You may also see the toilet's water level is sitting much higher or lower than usual. There might also be a sucking or gurgling sound when you flush. These factors may indicate a possible sewer blockage.

At this point, you should call Expert Plumbing & Gas Services, and we'll come out to assess the problem. We have the equipment and the experience to resolve the issue for you. Keep our number handy and save it to your phone: 03 9486 5907.

A blocked sewer is not a DIY issue. In your attempts to "fix" it, you may end up with a much larger problem and a costly expense to have the professionals come in and undo all your well-intentioned, hard work.