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Why Does My Kitchen Sink Drain Slowly? Understanding and Fixing the Issue

Why Does My Kitchen Sink Keep Backing Up?

A slow-draining kitchen sink is a common household problem that our Calgary Plumbers find time after time. It can be both frustrating and inconvenient, not only does it disrupt your daily chores, but it can also signal underlying plumbing issues that need to be addressed.

Understanding the causes and solutions for a slow-draining sink is essential for maintaining a functional and efficient kitchen.

Common Causes of a Slow-Draining Kitchen Sink

Food Debris and Grease Build-Up

One of the most common reasons for a slow-draining kitchen sink is the accumulation of food debris and grease in the pipes.

Over time, food particles and grease can adhere to the inner walls of the pipes, gradually building up and restricting water flow.

Clogged sink causing low water pressure

This type of clog often occurs in the P-trap, the curved section of the pipe under the sink designed to trap debris and prevent sewer gases from entering your home. Signs of this issue include a gradually slowing drain and unpleasant odors emanating from the sink.

Soap Scum and Chemical Buildup

Another frequent cause of slow drainage is the buildup of soap scum and chemicals. Soap, especially when combined with hard water, can leave a residue that sticks to the pipes.

Over time, this soap scum can combine with hair, grease, and other debris to form a stubborn clog. Similarly, household cleaning chemicals can react with other substances in the pipes, contributing to blockages.

Foreign Objects

Foreign objects accidentally dropped into the sink can also cause drainage problems.

Items such as small utensils, jewelry, or other non-biodegradable materials can get lodged in the pipes, leading to a slow drain.

It’s important to be mindful of what goes down your sink to prevent such issues.

Issues with Plumbing Ventilation

Proper ventilation is crucial for effective drainage.

Plumbing systems are designed with vents that allow air to flow through the pipes, facilitating the movement of water and waste.

If these vents become blocked or are not functioning correctly, it can cause water to drain slowly.

Common signs of ventilation issues include gurgling sounds and water backing up in other fixtures when the sink is draining.

Diagnosing the Issue

Initial Observations

The first step in diagnosing a slow-draining sink is to make initial observations.

Pay attention to how quickly the water drains and if there are any accompanying sounds or odors. Note if the problem occurs all the time or only intermittently.

These observations can provide clues about the nature of the clog.

Testing for Different Types of Clogs

To identify the type of clog, you can perform simple tests.

For example, fill the sink with water and observe how it drains. If the water drains quickly at first but slows down significantly, it could indicate a partial clog.


Conversely, if the water drains very slowly right from the start, the clog might be more severe.

Checking the P-Trap

The P-trap is a common location for clogs. To inspect it, place a bucket under the trap to catch any water, then unscrew the slip nuts and remove the trap.

Check for any debris or buildup and clean it thoroughly before reassembling. If the P-trap is clear but the sink still drains slowly, the clog might be further down the drain line.

By understanding the common causes and methods to diagnose a slow-draining kitchen sink, you are better equipped to address the issue effectively.

DIY Solutions for a Slow-Draining Sink

Dealing with a slow-draining kitchen sink doesn’t always require professional help.

There are several DIY solutions you can try to restore your sink’s functionality.

Here are some effective methods:

Using Boiling Water

One of the simplest solutions is to use boiling water. This method is effective for minor clogs caused by grease or soap scum. Here’s how to do it:

  1. Boil a kettle of water.
  2. Carefully pour the boiling water directly into the drain in two to three stages, allowing the water to work for a few seconds between each pour​ 
  3. This can help dissolve the grease and soap scum, allowing the water to flow freely.

Baking Soda and Vinegar Method

Baking soda and vinegar are a powerful combination for breaking down clogs. Follow these steps:

  1. Pour about one cup of baking soda down the drain.
  2. Follow with one cup of white vinegar.
  3. Let the mixture sit for about 15 minutes to allow the chemical reaction to work on the clog​.
  4. Flush the drain with hot water to clear out the loosened debris.

Plunging the Sink

Using a plunger can be very effective for unclogging a sink. Here’s how:

Unclog kitchen sink calgary

  1. Place the plunger cup over the drain and ensure it covers it completely.
  2. Fill the sink with enough water to cover the plunger’s cup.
  3. Vigorously plunge up and down several times to create suction and pressure, which can dislodge the clog​.
  4. Remove the plunger and check if the water drains smoothly.

When to Call a Professional

Sometimes, DIY methods may not suffice, especially for persistent or severe clogs.

Here are signs that you might need professional help:

Identifying Persistent Issues

  • If your sink remains slow despite trying multiple DIY methods, it could indicate a more serious blockage deeper in the plumbing system.
  • Recurrent clogs that clear up temporarily but return frequently might point to a systemic issue that needs professional attention.

Choosing a Plumber

  • Look for licensed and insured plumbers to ensure they have the proper credentials.
  • Check reviews and ask for recommendations to find reliable service providers.

We are highly rated Calgary Plumbers and have served the area for over 50 years. Instant Plumbing has a stellar online reputation and can assist you!

Preventative Measures

Preventing clogs is easier than dealing with them. Implement these preventative measures to keep your sink draining smoothly:

Regular Maintenance Tips

  • Regularly flush your sink with hot water to prevent grease buildup.
  • Use a natural cleaner like a mixture of baking soda and vinegar once a month to keep pipes clear.

Proper Disposal of Waste

  • Avoid putting grease, coffee grounds, and fibrous foods like celery or potato peels down the drain. Instead, dispose of them in the trash.
  • Use a sink strainer to catch food particles and other debris before they enter the drain.

Using Drain Covers

  • Drain covers can catch hair, food particles, and other debris before they go down the drain, preventing clogs from forming.

Routine Cleaning with Natural Solutions

  • Regularly clean your drain with a mixture of half a cup of baking soda followed by half a cup of vinegar. Let it sit for 15 minutes, then flush with hot water.


Why does my kitchen sink drain slowly even after using a plunger?

If your sink continues to drain slowly after using a plunger, the clog might be too deep or severe for the plunger to reach. It could also indicate a more serious issue like a blockage in the main drain line.

Can boiling water damage my pipes?

Boiling water is generally safe for metal pipes, but it can cause damage to PVC pipes if used frequently. Use boiling water sparingly and consider alternative methods for PVC plumbing.

How often should I clean my P-trap?

It’s a good idea to check and clean your P-trap every few months to prevent buildup and maintain proper drainage.

What are the best natural cleaners for my kitchen sink?

Baking soda and vinegar are excellent natural cleaners that can help maintain clear drains without the harsh chemicals found in commercial cleaners.


A slow-draining kitchen sink can be a nuisance, but with the right knowledge and tools, you can often fix the problem yourself.

By understanding the common causes and implementing regular maintenance practices, you can keep your sink draining smoothly and avoid the frustration of persistent clogs.

If DIY methods don’t work, don’t hesitate to call Instant Plumbing & Heating to ensure your plumbing is in top condition.

By addressing the issue promptly and effectively, you can maintain a functional kitchen and prevent more serious plumbing problems in the future.

George Pinel
George Pinel

Master Plumber

I have been involved in this family owned business for 33 years now.

It has always been and will continue to be the core focus of Instant Plumbing & Heating to provide a long lasting relationship with our customers based on trust and integrity of our service and products.

This achieved by using the best quality materials. I as a business owner continue to mentor and treat my staff with the highest regard and respect, this interns helps them deliver to the client great quality workmanship and service.

It is our professional goal to leave a situation better than when we arrived both in how we do our work and in how you feel for having chosen us to do your work, we are in the anxiety reduction business using plumbing and heating service work to do it.

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