5 Common Reasons Why Your Sink Smells Bad

There’s little that puts an end to the enjoyment of a clean kitchen or bathroom quicker than when your sink smells bad. The sour, rotten egg smell that hits you in the face and assaults your senses suggests a plumbing issue needing urgent attention.

Imagine coming home from work and wanting to get straight into preparing dinner. First and foremost, you want to chop up some vegetables, only it smells like someone (or something) has been doing the same thing. Deep within the pipes of your kitchen sink. Only they’ve also left the veggies out in the sun for three days as well. Hence, the sink drain smell.

There are many possible reasons why you might find yourself dealing with a smelly sink, whether it’s in the bathroom, the kitchen, or even in the laundry. Here are 5 of the most common reasons why.

Reason 1: Food Buildup in the Kitchen Sink Drain

Question. When you’ve finished dinner, what do you normally do with the scraps on your plate? Do you …

A) scrape them into the bin

B) feed them to the dog, or

C) wash them down the sink?

If you chose option C, you’re probably contributing to the smells coming from your stinky sink.

Food scraps and traces of grease often linger in the kitchen sink drain, particularly around the drain opening, trap, and sink strainer.

The decomposition of these food particles allows bacteria to thrive and release gases that cause the bad smell that travels up your nostrils. Grease coats the kitchen drain so debris sticks, leaving water draining slowly and odours hanging around – like a bad smell – long after you’re done washing up.

To tackle the problem head-on, flush your clogged kitchen sink with hot water and some dish soap to emulsify fats. But if you have PVC pipes, DO NOT use boiling water as you’ll likely damage them. Scrub the strainer and plug, and empty the basket.

Underneath your bathroom or kitchen sink, you’ll find what is called a P-trap.

Despite its name, the P-trap’s U-shaped bend contains a small water seal that blocks sewer gases from entering your home. If you haven’t used a particular sink in a while, the water evaporates or poor venting siphons it out. This breaks the seal and causes your unpleasant sink drain smells. You might notice it after pressure changes or when fixtures discharge.

To fix the issue, refill the P-trap by running hot water for 30 seconds, and be sure to top up rarely-used sinks in your house monthly. Check for leaks or a loose trap, and make sure the vent isn’t blocked.

The Plumbing Code of Australia references AS/NZS 3500, which requires that sanitary plumbing be vented and trap seals protected. If your sink smells bad, book a licensed plumber to investigate the possibility of sewer gas ingress.

When you’re standing under the shower or washing your hands at the bathroom sink, hair and soap scum wash down the drains. They bind and form a mat that narrows the pipe and feeds odour-causing bacteria. The outcome is a slow, clogged drain that can go a long way toward making your house smell bad.

In this instance, the best way to tackle your smelly drain problem is to remove the pop-up. Clean the drain opening and overflow hole, and pull any built-up gunk with a plastic drain snake. Flush with hot water and dish soap to break down any remaining residue.

For lingering odours, add half a cup of baking soda down the sink (or shower drain), then white vinegar; wait 10 minutes and rinse with hot (not boiling) water afterwards. If the sink smells bad and keeps returning call a licensed plumber.

Biofilm is the sticky, slimy substance that often coats hidden surfaces like the overflow hole, drain plug assembly and underside of the sink basin. Built by microbes, this layer traps food particles and soap scum. What that does is feed bacteria, which results in a smelly kitchen sink.

Resolve the issue by scrubbing the drain opening and plug with dish soap. Follow that up by flushing with hot water to loosen residue. Add half a cup of baking soda, followed by white vinegar, and let it fizz for 10 minutes before rinsing with hot water.

As we’ve mentioned above, avoid pouring boiling water into PVC pipes if possible, as it can seriously damage them. If it doesn’t take long before your sink smells bad again, disinfect the overflow with a brush and schedule professional drain cleaning service.

Persistent odours coming from your kitchen sink and/or bathroom sinks often indicate significant sewer line problems or a blocked vent. And that’s something you want to get on top of quick smart.

Tree roots, collapsed drain pipes or a misgraded line trap wastewater and push sewer gases (and their associated sewer smells) back through traps. A blocked vent stack stops air from entering, so fixtures gurgle and drains run slowly.

Warning signs include a distinct rotten egg smell in the house, toilet bubbling and recurring blocked drains. Check vents and gully grates for obstructions. In Australia, repairs require a licensed plumber under AS/NZS 3500. Expect CCTV inspection, jetting or sectional replacement by a professional drain cleaning service when your sink smells bad.

To say goodbye to sink stink and adios to smelly bathroom drains, use these safe, practical steps that also protect PVC pipes and align with Australian practice.

• Flush with hot water (not boiling) to warm your kitchen sink drain and loosen grease.
• Add half a cup of baking soda, then white vinegar; let it fizz for 10 minutes and rinse with hot water.
• Run hot water with a little dish soap to emulsify residue.
• Scrub the drain opening, sink strainer, drain plug and overflow hole.
• Pull out hair and soap scum with a plastic drain snake.
• Steer clear of caustic chemicals that can damage pipes and traps.

If the sink smells bad or sewer gases persist, book a licensed plumber ASAP.

Enjoy Fresh Sinks and a Fresher Home

From food buildup and biofilm to dry traps and vent issues, most smelly drains are solvable with steady habits and smart checks.

Keep the kitchen sink drain clear, flush residue with hot water, and use baking soda and vinegar safely on PVC pipes. Clean the overflow hole and strainers, catch food particles, and act early on draining slowly.

If a sink smells bad, scan for sewer gases, gurgling or house-wide odours that suggest a bigger blocked drain or sewer line problem. That’s the time to call a licensed plumber or a professional drain cleaning service to restore your plumbing system and keep your kitchen sink smelling clean.

Please note: Thanks for reading our blog “5 Common Reasons Your Sink Smells Bad”. This information is provided for advice purposes only. Regulations differ from state to state, so please consult your local authorities or an industry professional before proceeding with any work. See our Terms & Conditions here.