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How to clean a smelly drain

How to clean a smelly drain

Smelly drains are unfortunately a common problem in many households. The good news is, it’s usually an easy problem to resolve and one that can be done without having to call a plumber (in most cases).

What Causes Smelly Drains?

A smelly drain can be a sign that things are going awry in your pipes. The most common causes of smelly drains include:

A Sewer Gas Trap Problem: 

Every piping system has a P-trap. In bathrooms, one side of the U-shaped pipe is connected to the septic system, while the other runs up to the roof. This allows for bad smells to exit the house and fresh air to come in.

The purpose of a bathroom P-trap is to protect the home against sewer gasses by collecting water after every tap use or toilet flush. The water acts as a trap and stops the gas from escaping into the home.

In kitchens, the P-trap is commonly used to trap food and other waste that has been passed down from the sink and stops it from causing a blockage in the plumbing system.

This problem occurs mainly in taps that don’t get much use.

Food and Organic Buildup: 

It’s easy for food and other organic materials to get caught in pipes without us noticing, however, it’s soon hard to ignore when the food and organic material starts decomposing and attracting bacteria which results in a bad smell.

Old Pipes: 

This is a more common problem found in houses built before the 1980s where pipes were made from clay joined with cement. These old school pipes are not crack-proof so any movements underground can easily cause damage which leads to blockage and a build-up of sewage.


If your drain smells musty, it’s most likely mould causing the smell. Mould grows wherever there’s moisture making it a common fixture of drains. It releases tiny puffs of gas which smells and can potentially be harmful to inhale (can cause headaches and dizziness).

Tree Roots: 

Tree roots seek moisture so it’s only natural that they will be drawn to wet and warm pipes. Once they find a water source, they grow and this can cause your pipes to become blocked. If you hear gurgling noises when you flush the toilet or use the tap, it could be because you have a tree root problem. The best cause of action for resolving this is to call professional tree removalists, who will remove the roots without causing any damage to the surrounding trees or your pipes.

Drain Flies: 

Drain flies (also known as sink flies) may be tiny but they’re still a nuisance. Drawn to places with decomposing organic matter and stagnant water, they will lay their eggs in drains and sewage pipes. Drain flies multiply quickly and are capable of causing a bad smell if there’s a large amount of them.

How to Clean Smelly Drains:

Getting rid of a smelly drain is easier than a lot of people think and can usually be done by using supplies already found in your home.

Here are some handy tips and tricks to help you get rid of those nasty smelling drains:

Baking Soda and Vinegar: 

This is the most common and effective method used to get rid of bad odours in your drains. Follow these steps:

  1. Pour hot water down the drain which will loosen any gunk.
  2. Pour half a cup of baking soda down the drain and let it rest for a few minutes. This allows the hot water and baking soda mixture to work on eroding the grime.
  3. Mix one cup of vinegar and a cup of boiling water and pour it down the sink. This results in a chemical reaction which loosens any remaining debris.
  4. Cover the drain with a plug or sponge which lets the chemical reaction do its thing below the surface of the drain. Leave it for 5-10 minutes.
  5. Finish off by pouring another cup of boiling hot water which will wash away any lingering grime.
  6. Repeat the process if necessary.

Boiling Water and Vinegar: 

  1. Pour half a pot of almost boiling water and vinegar down the drain.
  2. Wait a few minutes and rinse the sink with cold water.
  3. Pour the rest of the vinegar and hot water mixture down the sink.

Remove Mould: 

  1. Mix baking soda and hot water together until it creates a paste.
  2. Use an old toothbrush to apply it to the drain and let it sit for 10 minutes.
  3. Scrub the drain with the toothbrush until the mould begins to disintegrate.
  4. Pour boiling water down the drain.
  5. Pour a cup of water and half a cup of baking soda down the drain.

Why does the baking soda and vinegar solution work best? 

  • Baking soda reacts well with boiling water and kills odours.
  • Vinegar contains acetic acid which neutralises any smells.
  • Environmentally friendly (natural and non-toxic).
  • Everyday items are already found in homes.
  • When mixed together they form carbon dioxide and sodium acetate (bubbles). which effectively scrub the drain.

How do you prevent smelly drains? 

Prevention is always better than trying to find a solution. Doing some simple maintenance can prevent smelly drains from becoming a problem. Here are some easy ways to keep your drains smelling fresh and clean:

  • Boiling water: Tip boiling water down the drains in your house about once a week.
  • Baking soda, vinegar & boiling water mixture: Once a month, do the baking soda, vinegar, and boiling water method.
  • Clean your garbage disposal: If you have a garbage disposal, regularly put ice cubes into it which will get rid of any excess grease and will give the blades a good scrub. Also cut up a lemon or orange into small wedges and put it into the garbage disposal – this leaves it smelling fresh.
  • No fats & oils: Avoid putting oils and fats down your sink.
  • No food scraps: If you don’t have a garbage disposal, make sure all food scraps go into the bin or get fed to pets instead of going down the drain.
  • Strong drain cleaners: Use strong, commercial drain cleaners if nothing else works.
  • Maintain regular tap use: Make sure you regularly turn on the taps in your rarely used bathrooms. This ensures that there’s no build-up of grime and prevents your P-trap from becoming empty and releasing sewer gases into the house. 

What supplies do I need? 

Everything you need to effectively clean your drain can already be found in your home, making it convenient and affordable. The main items you’ll need include:

  • Boiling water
  • White vinegar
  • Baking soda
  • Rubber gloves
  • Plug

What do I do if my drains still smell? 

If you’ve tried multiple methods to clean your drains, and none of them have been successful, it might be time to call in the professionals. Give Sydney Emergency Plumbing a call on 1800 862 565 for a fast, reliable response. With over 20 years of experience, we specialise in 24-hour emergency plumbing services to give you peace of mind.

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