Domestic Help & Advice Drainage Problems Why does my sink smell?

Why does my sink smell?

Sometimes, even after you have scrubbed your sink, blitzed your bathtub and cleaned your counters, nasty smells can still linger in and around your bathroom and kitchen areas.

On closer examination, the smell might be coming from the plughole in your sink and it might smell like rotten eggs, or even raw sewage. But what causes that to happen and what can you do about it?

Your drainage system

Before we discuss the reasons why your sink might smell, it’s important to first understand the parts of the drainage system that are typically involved in this problem.

Waste traps

There are many different types waste traps used in the home, but ultimately, they all serve the same purpose: to prevent sewer gases from re-entering the home.

They are typically found below or within a plumbing fixture within the home, and are shaped in such a way that ensures there is always a small amount of water retained within the trap. The water that remains in the trap acts as a shield to block sewer gases from entering the home from the foul water pipes your system is connected to.

Traps only work if they are sufficiently vented – this equalises the pressure within the pipes to allow sewer gases to escape safely.

There are numerous types of waste trap that are present in the typical British home, including:

  • U-bend; typically used in kitchen sinks
  • S-bend; also used in kitchen sinks
  • Bottle trap; used in pedestal basins
  • Washing machine S-bend; used for washing machines

When you flush the toilet, pour dirty dishwater down your kitchen sink, or brush your teeth, the water you’ve used – foul water, or waste water – leaves your household and enters the main drainage system in your area via foul water pipes and drains. Each foul drain pipe takes water into a manhole or inspection chamber before entering the sewer system.

Grease traps

A grease trap is a piece of equipment that is installed to capture fats, oils and grease (FOG) from sink waste to avoid it entering the drains and subsequently the sewage system. They’re usually only found in commercial properties, because they’re legally obliged to ensure FOG doesn’t enter the drainage system

Why your sink smells

There are typically four common causes of foul smells from plugholes in the home:

  • Food debris
  • Fats, oils and grease (FOG)
  • Sewer gases
  • Hair blockages
  • Waste disposal units and macerators

Waste disposal units and macerators are devices that are designed to grind food waste into pulp for ease of disposal. Unfortunately, they’re bad for our sewers because by grinding up fatty foods, it makes it easier to rinse down our sinks and stick to inside of pipes and our sewer walls. It can cause blockages, flooding and rodent infestations.

Food debris

When plates with leftover food aren’t scraped or cleaned properly before being washed in the sink, the waste can collect in the pipes underneath your sink.

This waste gets captured by the biofilm in your U-bend, and ultimately, ends up blocking your sink and causing that awful smell.

FOG

In addition to FOG, which might go down the drain after cooking, the likes of hair, skin cells, toothpaste, shaving foam, food, tea, coffee can find their way down our plugholes and into our pipes.

All of these substances can get caught on the lining of your sink drainage system – either in the the pipes themselves, in waste traps or in grease traps. When FOG and these other items get caught in traps or build up in pipes, they can rot, decay and cause that foul smell.

Hair blockages

Particularly in the bathroom, your sink, bath or shower may become blocked – and it’s usually because of hair you shed when you wash.

Hair accumulates in your plughole and mixes with shampoo, shower gel, shaving foam and other substances to create congealed masses of hair. It is these masses that get stuck in your plughole and cause your sink to become blocked and smelly.

Sewer gases

We mentioned earlier that waste traps retain water to act as a barrier to stop sewer gases entering the home. But sometimes these traps fail.

If the drainage system is not properly vented, it can lead to high pressure in the drains. This can result in:

  • Drains forcing sewer gases out of the traps and into the home
  • Gurgling and bubbling in the fixtures

A low pressure environment can also occur if there is a problem with the venting in the drains. This could lead to:

  • Siphoning in the traps whenever plumbing fixtures are drained
  • Dry traps, which means the liquid ‘airlock’ that blocks sewer gases from entering the home is ineffective

How to clean waste traps and plugholes

DIY solutions for cleaning U-bends

If you think the problem has been caused by a build-up of FOG in your drainage system, you can attempt to clean your waste traps yourself.

You will need to set aside about 15 minutes or so, and ensure that your sink doesn’t have any water in it.

The process is pretty standard for each type of trap, so you’ll only need these basic household supplies:

  • Kitchen roll
  • Long pipe brush
  • Plastic container or bowl
  • Spoon or knife for scraping
  • Rubber gloves
  • ToothbrushBleach
  • Adjustable wrench (if required)
  1. Place a tub or bowl underneath the waste trap in your sink. In most cases this will be the U-bend type. You’ll need to loosen the union nuts holding the U-bend in place.
  2. In most cases this can be done by hand, but sometimes, you’ll need a wrench to loosen them. Remember, the U-bend will contain water, so this is where your bowl or container will come in handy.
  3. Set the U-bend to one side and grab your chosen scraper and scrape any black residue away that may have accumulated in the pipe that leads outside.
  4. Get a wad of kitchen roll and roll it up into a cylindrical shape. Push it directly into your sink where your plughole once was and chase it down with the pipe brush until it comes out where your U-bend normally is. Repeat this action several times until you’ve captured a significant amount of gunk from your sink.
  5. Turn your attention to the U-bend. Put it in your bathtub and fill it with enough water to submerge it. Add a couple of capfuls of bleach and let it soak for about 15 minutes or so and then take them out.

Now, reattach the U-bend to your sink. Make sure the fitting is on tightly to avoid any leaks. Boil your kettle and bring it to your sink. Pour it down your freshly cleaned sink for a final cleanse and check to see if there any leaks. If there are no leaks, the job is complete.

DIY solutions to clean hair from your sink

If you think the blockage in your sink is caused by hair, you can attempt to tackle the problem yourself. There’s plenty of things you can try before thinking about calling out the professionals.

  1. Bicarbonate of soda and vinegar – mix together about a ⅓ of a cup of baking soda with a ⅓ of a cup of vinegar, then carefully place it down the problematic plughole. It’ll start to fizz and spit, which should remove any hair and grime. Leave it for about an hour or so and then rinse it out with a kettle of boiling water.
  2. Tweezers – for fast results, and if you’re able to take off your plughole, consider using tweezers. Remove the plughole cover and start grabbing and pulling hair with the tweezers.
  3. Hair removal cream – traditionally used for health and beauty applications, this cream can be used on your drain to break down hair. Simply empty an entire tube of the cream into your sink, wait for an hour, and then thoroughly rinse your plughole with water to rinse away your blockage.
  4. Plunger – if you have a significant build-up of grime, soap and hair, and you’ve tried our other tips, you might want to try and use a plunger to unblock your sink. Start by creating an airtight seal with your plunger over the plughole, and then, move the plunger up and down. This creates suction, likely moving the hair blockage closer to your plughole, allowing you to fish it out.

Expert solutions

If there’s evidence of grease deposits, we would strongly recommend that the drains are de-scaled professionally via water jetting.

At Lanes, our specialist engineers employ electro-mechanical, high-pressure jetting and vacuumation units to clear tough blockages and ensure your drainage system works as it should in no time at all.

Stopping your sink from smelling in the first place

We always say prevention is better than cure when it comes to drainage systems – and this is no exception for your sinks – so don’t wait for a problem to occur before acting.

The most important thing to remember is to avoid putting things down your sink or drains that could cause any sort of blockage. The ‘Main Offenders’ to avoid are:

  • Fats, oils and grease (FOG)
  • Wet wipes
  • Nappies and pads
  • Sanitary products
  • Tampons, applicators and wrappers
  • Condoms
  • Razor blades
  • Bandages and plasters
  • Dental floss
  • Medicines and syringes
  • Cotton buds
  • Hair

Read our full blog post on the simple steps you can take to stop your drains from smelling.