Have you ever gone to your basement or home office only to be greeted by a foul smell?

If this smell is similar to that of rotten eggs, then it’s likely coming from your drains. This is because the rotten egg/sulfur smell is one created by the compounds found in sewage.

While not all blockages will cause this odour, it’s generally a sign that grease or fat is stuck in the drains. If you think you may have a blockage, continue reading for more information and don’t hesitate to contact a professional if the problem persists.

The Cause of the Smell

When sewage decomposes, it releases hydrogen sulphide gas. This gas is what gives off that “rotten egg” smell. If this gas is coming from your drains, it’s likely because there’s a blockage somewhere in your plumbing.

When grease and fat build up in your drains, it can create a seal that traps gas and sewage below it. As the debris decomposes, the hydrogen sulphide gas builds up and eventually escapes through tiny cracks or holes, causing that foul odour. In some cases, you may also see bubbles coming up through your drains when you turn on the water.

If you notice this sewage smell often, it could be due to vent stack problems. The vent stack allows gases to escape from your home so they don’t build up and cause odours. If there’s a blockage in the vent stack, it can cause gases to back up into your home through the drains.

This is why it’s essential to have a professional take a look if you think you may have a blocked drain. The problem could be more significant than you think!

Why You Should be Concerned

If you’re smelling hydrogen sulphide gas, taking action immediately is essential as it could indicate a much bigger problem.

While the gas itself isn’t toxic, it can react with other chemicals to create sulfuric acid – which is highly corrosive and toxic. When left unaddressed, the rotten egg smell can become overwhelming and make breathing difficult.

In some cases, it can even lead to nausea and vomiting.

How to Get Rid of the Smell

If you think your drains are responsible for that rotten egg smell, you can do a few things to eliminate the odour.

  • First, identify the source of the smell. In most cases, the odour will be most robust near the drain.
  • Next, clean out any build-up in your drains. This is often caused by grease or solidified fat stuck in your drains. To remove the build-up, you can use a plunger or snake to break up the clog and clear it out of your drain.
  • Once you’ve removed the build-up, pour boiling water down your drain to flush out any lingering particles. You can also use vinegar or bleach as alternatives to boiling water.
  • Finally, pour baking soda down your drain and follow it with cold water. Baking soda is a natural deodoriser that will help neutralise any foul smells coming from your drains.

Preventing Blockages

Now that you know what causes those terrible smells emanating from your drains, you’re probably wondering how to prevent them.

To start, be mindful of what you’re putting down your sink! Avoid pouring grease or oil down the drain, as these are two of the main culprits of drain blockages. You should also avoid putting coffee grounds or eggshells down the drain, as these can contribute to clogs forming over time.

In addition to being mindful of what goes down your drains, you should also have them cleaned regularly by a professional. This will help remove any potential build-up before it becomes a full-blown blockage.

Regular cleanings will also help keep bad smells at bay.


The next time you go downstairs and are hit with a wave of stink, check to see if it smells like rotten eggs.

If so, there’s a good chance that something is blocking your drains and causing sewage gases to escape. To prevent this from happening, avoid pouring grease or oil down your drain and have your drains cleaned regularly by a professional plumber or drain cleaning company.

If you’re experiencing sewage smells in your home, don’t wait to call us. Our professionals can help identify the source of the problem and take corrective action. Contact us today for more information!