Homeowner Guide

Why Does My Kitchen Sink Keep Blocking, and How Do You Prevent It?

A kitchen sink that keeps blocking almost always comes down to one thing: fat. Here is why it happens and how to stop it happening again.

Keith, Owner | September 2026

A kitchen sink that keeps blocking almost always comes down to one thing: fat. Grease, cooking oil, and the fat off your plates go down as a warm liquid, then cool and harden inside the pipe. Add food scraps and a bit of soap scum, and the gap the water flows through gets narrower every week until the sink drains slowly or stops altogether. The good news is that it is one of the easiest blockages to prevent.

Prevention really is the key here. Keep fat and food out of the sink, and most kitchen blockages simply never form. A+ Drainage Services clears blocked sinks across Essex, London and the M25 corridor when they do happen, with no callout fee and no harsh chemicals. Here is why your sink keeps blocking and how to stop it happening again.

Why Does My Kitchen Sink Keep Blocking?

The main culprit is fat, oil and grease, often shortened to FOG in the trade. It pours away easily when it is hot, but it does not stay liquid for long. As it cools in the pipe, it clings to the walls and hardens, and every future pour adds another layer. Food scraps then make it worse. Starchy leftovers like rice and pasta swell in water, coffee grounds clump together, and both get caught in the sticky fat that is already there. Most of this collects in the U-bend, the curved section of pipe under the sink, which is exactly where a kitchen blockage tends to form.

How Do You Prevent a Kitchen Sink From Blocking?

Most of it comes down to keeping fat and food out of the pipe in the first place.

Bin the Fat; Do Not Pour It

Let cooking fat and oil cool in the pan, then scrape it into the bin or an old jar. This one habit prevents the majority of kitchen blockages.

Scrape Plates Before Washing

Get food scraps into the bin or caddy rather than rinsing them down the sink.

Fit a Sink Strainer

A cheap mesh strainer over the plughole catches scraps and stops them going down at all. Just empty it into the bin.

Flush Through With Hot Water

After washing up something greasy, run the hot tap for a minute with a squirt of washing-up liquid to move any residue along.

Keep the Wrong Things Out

Coffee grounds, rice, pasta and similar swelling or clumping foods belong in the bin, not the sink.

Keep These Out of the Plughole

What Should You Never Put Down a Kitchen Sink?

A few things cause more trouble than the rest, so keep them out of the plughole entirely.

Fat, Oil and Grease

Of any kind.

Coffee Grounds

They clump together and catch on fat.

Rice, Pasta and Starches

They swell in water and pack tight.

Flour and Paste-Makers

Anything that turns to paste in water.

Eggshells and Peelings

They bind with fat and clog the pipe.

None of these breaks down in the pipe. They either set hard, swell up or bind with the fat that is already there, and all of them shorten the time until the next blockage.

How Do You Clear a Kitchen Sink That Is Already Clogged?

If it is already draining slowly, there are a couple of safe things to try before calling anyone. Cleaning the U-bend is the most effective: put a bucket underneath, unscrew the trap, clear out the gunk by hand, then screw it back on. A cup plunger over the plughole can also shift a blockage closer to the surface, especially if you block the overflow first to keep the pressure sealed. Steer clear of chemical drain cleaners, though. They struggle with a solid fat blockage, and they can damage your pipes into the bargain.

When Should You Call a Professional?

If cleaning the trap and plunging do not fix it, the blockage is further down the waste pipe than you can reach, and that is the point to call someone in. The same goes for a sink that keeps blocking, however careful you are, since that usually means a build-up deeper in the system. A professional can clear it properly and, if it keeps returning, look at what is causing it rather than just shifting it again.

How A+ Drainage Services Helps

When a sink is beyond a home fix, we clear it without harsh chemicals and without mess. We check whether the blockage sits in the trap or further along the waste pipe. Then we take the pipework apart where we need to and pull out the fat, grease and debris by hand.

Because we are working in your kitchen, we cover surfaces, wear shoe covers and leave everything clean once the water is running freely again. You get a clear price up front, and there is no callout fee.

500+ Five-Star Reviews

Frequently Asked Questions

Quick answers to common questions about kitchen sink blockages.

Kitchen Sink Still Blocking? Call A+ Drainage Services

Fighting a losing battle with a kitchen sink that keeps blocking? Call Keith and the team for a proper, chemical-free fix with no callout fee.