A sink overflow hole is a small hole located on the back of the sink that helps prevent water from overflowing and flooding your bathroom.
The hole is important because it allows excess water to drain out of the sink and into the overflow pipe.
It is easy to forget about this little hole when you clean your bathroom. But if it’s gunked up with soap scum and hair, it can develop foul odors, leading to unpleasant smells in the bathroom.
Today I have some tips and tricks on how to unblock an overflow drain and get rid of the nasty odors deep inside.
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The causes of bad smells in the bathroom sink overflow hole
If you have a smelly bathroom, and you think it is due to the overflow hole, here are the most likely causes:
- Clogged overflow drain. Over time, hair, soap scum, and other debris can accumulate in the overflow drain, causing a clog that leads to stagnant water and an unpleasant odor.
- Gunk buildup. When the overflow hole is not cleaned regularly, a buildup of gunk and grime can occur, leading to foul smells in the bathroom.
- Plumbing issues. Sometimes, a plumbing issue like a broken or leaky pipe can cause stagnant water to accumulate in the overflow drain, leading to a bad odor.
- Stagnant water. When water is left to sit in the overflow drain for an extended period of time, it can develop a foul odor due to bacteria growth.
In the following sections, I will share my tips and tricks for unblocking the overflow drain and getting rid of the foul odor.
How to unblock an overflow drain
If your sink overflow hole doesn’t drain, you won’t be protected from a flood should anyone leave a tap on in the sink.
So, it’s important to unblock it immediately.
You can unblock the drain hole by pushing a pipe cleaner, plumbing snake or long cable tie down as far as it will go and then twisting it to loosen blockages.
I found that plumbing snakes (also known as an auger) are the most effective due to their plastic teeth which grab onto the dirt and dislodge clogs.
They work brilliantly too for removing hair from the shower drain.
All you need to do is push the plumbing snake all the way down, twist, and then bring it up again, and then repeat as necessary.
When the pipe is clear, follow the steps below to flush out even more gunk and make it smell fresh again.
How to clean your bathroom sink overflow hole
Now you have your sink overflow unblocked, let’s find out how we can clean it some more and make it smell good again.
Things you will need
- Baking soda, washing soda crystals or enzyme cleaner
- Distilled white vinegar
- Silicone or plastic funnel that will withstand hot water
- Microfiber cloth
- Boiling water
- Household gloves
Step 1 - Wipe with a microfiber cloth
I like to start by wiping the inside of the little hole with a damp microfiber cloth.
Push it in as far as it will go and twist.
You should find that the gunk sitting at the top of the drain should come away.
Step 2 - Pour in cleaning solution
Next we will pour in some cleaning solution. There are several solutions we can use for this.
My advice would be to use whatever you already have available.
I find that washing soda crystals and vinegar or hot water work really well.
You will need a suitable funnel for this, as it is tricky to get cleaning chemicals down the hole without one.
Choose one that can withstand boiling water.
Dish soap method
Pour in a large amount of dish soap down the sink hole. Leave it to sit for an hour or so. Then pour down some hot water.
Baking soda and hot water method
Mix a cup of baking soda with warm water and pour it down the drain.
Let it sit for 10-15 minutes before flushing with hot water.
Washing soda crystals and hot water method
Washing soda crystals are a fantastic degreaser, and are great as dissolving gunk and scum.
Mix a cup of washing soda with warm water and pour it down the drain.
Let it sit for 10-15 minutes before flushing with hot water.
A cup of distilled white vinegar can also be used to remove bad smells from the sink overflow hole.
Simply pour the vinegar down the drain and let it sit for 10-15 minutes before flushing with hot water.
Baking soda and vinegar method
- Put the funnel into the hole.
- Pour in as much baking soda as you can. Alternatively, use washing soda crystals, as they work very well too.
- Next, pour the vinegar down the funnel. When the vinegar hits the baking soda, it will fizz and start to dissolve the gunk inside the overflow hole.
- Let this sit for half an hour.
- Flush with boiling water.
Enzyme cleaner method
Enzyme drain cleaners can also be used to eliminate any foul odors in the sink overflow hole.
Simply pour the cleaner down the drain and let it sit for 10-15 minutes before flushing with hot water.
Top tip: If you don't have an enzyme cleaner to hand, some dissolved biological washing detergent or a dissolved dishwasher tablet will work too because they both contain enzymes in their ingredients.
Step 4 - Pour in some boiling water
Boil your kettle or boil a jug of water in your microwave and then pour it down the drain hole.
Step 5 - Clean around the sink
Now you have a clean drain, the next thing to do is to clean the whole sink.
I find that nasty stuff often splashes into the sink whenever I clean the drain.
Add a few drops of dish soap to the sink and then wipe all around it with a new microfiber cloth.
How to prevent your bathroom sink overflow hole from smelling
Now you know how to get your sink overflow clean and fresh, how do you keep it that way?
To prevent bad smells from returning, it is a good idea to clean the overflow hole regularly.
Pour some boiling water down the hole every few weeks. If it starts to smell again, repeat the cleaning process outlined above.
Frequently asked questions
Why does my sink hole smell like rotten eggs?
A foul smell that resembles rotten eggs often indicates the presence of sulfur in the water. This can be caused by a buildup of bacteria in the sink’s overflow hole, and can result in a sewer-like odor.
If you notice this type of smell coming from your sink, it is important to clean the overflow hole as soon as possible.
Regular cleaning and the use of enzyme drain cleaners can also help prevent the smell from returning.
Why does my bathroom smell like a sewer?
If your bathroom smells like a sewer, it is usually caused by a clogged sink overflow hole or drain, a slow-moving drain, or a plumbing issue.
Cleaning the sink overflow hole and using a drain cleaner can help resolve the issue, but you may need to seek the help of a professional plumber if the problem persists.
Can you put bleach down the overflow hole of the sink?
It is not recommended to put bleach down a sink overflow hole. The chemicals in bleach can damage the pipes and cause plumbing issues.
Instead of bleach, there are other cleaning solutions that can effectively clean the sink overflow hole without damaging the pipes. These solutions include hot water, vinegar, baking soda, and enzyme drain cleaners.