Why Does My Kitchen Sink Keep Backing Up? Here’s Why & What to Do

Quick Answer 

When a kitchen sink backing up, it is nearly always due to a grease, food particle, or soap scum build-up trapped in the P-trap or main drain line, and if a plunger or store bought cleaner can only unclog the sink for a day or two, then the clog has gotten deeper in the pipe. It features a breakdown of the true causes, do-it-yourself solutions that work and when to hire a licensed plumber.

Why Does My Kitchen Sink Keep Backing Up? 

The most common cause of kitchen sinks backing up over and over is that there is a lot of grease, coffee grounds or food bits that have built up in the drain pipe, and it has become so narrow that the water can no longer pass through quickly. Kitchen drains are different from bathroom sinks, because oils and fats solidify in the walls of the pipe when they cool, and everything else that flows through the pipe clings to it.

Here are the most common culprits:

• Cooling Of Grease And Cooking Oil Deposition: Fat doesn’t go away, it cools and sticks to the sides of the pipes, causing the drains to become clogged over time.
• Food Particles And Coffee Grounds: No matter how well you do the job, small bits of food and coffee grounds grow over time.
• Dish Soap Residue And Soap Scum: A build up of film from the dish soap that can collect dirt.
• The Blockage In The P-Trap: Debris accumulates in the curved pipe located under the sink, and it eventually clogs.
• Multiple Slow Drains In The Home: The problem may be down the line as well; a blocked main sewer line.
• A Clogged Or Worn Out Garbage Disposal: A clogged or worn out disposal may be sending food back up.

Key takeaway: If just your sink is clogged, the blockage is a local one. If your bathroom or basement drains are also backing up or gurgling, it’s probably a problem with your kitchen sink drain backing up into the common sewer pipe.

Kitchen Sink Clogged? Signs You’re Dealing With More Than a Simple Blockage 

A kitchen sink clogged often drains slowly and with a “gurgle” sound; a large clog will cause water to back up, back over, or flow back into the sink after trying to unclog it.

Watch for these warning signs:

1. Water drains slower each day, even after cleaning
2. Gurgling noises coming from the drain or nearby fixtures
3. A foul, sulfur-like odor rising from the sink
4. Water backing up into the sink when the dishwasher runs
5. Standing water that doesn’t fully clear overnight

Two or more of these signs are definitely a sign that the blockage is past the P-trap and into the branch or main line of your home’s drain.

Kitchen Sink Clogged, Tried Everything? Here’s What Actually Works 

If you’ve tried everything from hot water, dish soap and even a plunger, but nothing has resolved the kitchen sink clogged, it’s probably too deep or dense for the surface remedies. At this stage, self-reliant techniques have a certain limit and repeated attempts may sometimes be able to push the blockage further into the pipe.

Step-by-Step DIY Fixes to Try First

1. Bring water to a boil and slowly pour in the water in two or three stages, waiting 1 minute between each pour.
2. In the case of an overflow hole, cover it with a plunger and plunge for 15-20 seconds.
3. Do pour ½ cup baking soda into the drain and then ½ cup vinegar, cover the drain, and wait 15 minutes while it bubbles.
4. Inspect and clean the P-trap, put a bucket under it, unscrew the P-trap, and remove any debris caught in P-trap.
5. Feed the hand auger into the drain using a drain snake and unclog or dislodge the clog by hand.

Expert tip: Do not use chemical drain cleaners for reoccurring clogs. They can break down older pipes as well and just partially get rid of the blockage, creating a false impression of a solved issue.

Kitchen Sink Clogged Solution: DIY vs. Professional Repair 

The kitchen sink clogged solution will vary based on the location of the clog. If there is a clog near the drain opening, it may be possible to clear the clog with a DIY method, but once it’s beyond the P-trap, you generally need to use a motorized auger or hydro jetting machine to clear it completely and forever.

Disclaimer: The prices shown are general estimates for reference only and are not official pricing from BOS Plumbing & Drains. Actual costs may vary based on the specific job and site conditions.

Common Mistakes That Make a Kitchen Drain Backing Up Worse 

• Pouring grease down the drain, even with hot water running it re-solidifies further down the pipe.
• Overusing chemical cleaners, which can eat through old galvanized or cast iron pipes.
• Ignoring slow drains, letting a minor clog turn into a full backup.
• Running the disposal with fibrous foods like celery or potato peels, which wrap around the blades and jam the line.
• Mixing baking soda, vinegar, and chemical cleaners together, which can create pressure buildup or harmful fumes.

When to Call a Professional Plumber 

If your kitchen sink backing up problem keeps recurring within days of plumbing cleanup, if more than one sink has the problem, or if it is accompanied by sewage odors, it is time to call in a licensed plumber – that’s an indication the plumbing problem is located in the main line which DIY tools cannot reach safely. Using a professional camera inspection will provide an accurate diagnosis rather than a “best guess” and make the savings not just in the short run but long term.

This is where BOS Plumbing and Drains can help. BOS Plumbing and Drains has been providing homeowner services throughout the Greater Toronto Area for 20+ years, and has established a trusted reputation with the community as a same day plumbing services and residential plumbing company. Their qualified and insured staff members have the ability to locate and remove blockages at the source of the problem rather than just push them downstream with camera inspection, drain snaking and hydro jetting.

BOS Plumbing and Drains is a full-service plumbing company that provides no hidden charges for its services, no-cost expert advice, and 7/24 emergency plumbing services if there’s a backup that needs attention ASAP. They offer a 25-year transferable warranty for sewer and water line work, providing homeowners with long-term peace of mind and not a quick fix. Their local teams are also available in Oakville, Milton, Niagara, Toronto, Brampton, and North York to offer the same fast, clear, plumbing repair service.

Key Takeaways

• Routine kitchen sink backing up is typically due to grease, food or soap residue and is not a fluke.
• Minor, surface level clogs can be addressed with a DIY fix such as plunging, boiling water or baking soda.
• If the clog happens again soon or multiple drains are clogged, the problem is in your main line and requires professional tools.
• Do not pour grease down the drain or use chemicals as cleaners; limit use of chemicals as cleaners to protect pipes for long-term protection.
• BOS Plumbing & Drains are Mississauga’s 24/7, same day plumber with a 25 year transferable warranty for work on sewer and water lines.