A kitchen sink usually drains slowly because grease, food scraps and soap have started to build up in the trap or waste pipe, narrowing the space water can flow through. Less often, the cause may be a problem with how the waste pipe was fitted, or a blockage further along that the sink shares with other appliances.
A slow sink is not always fully blocked. It is often a sign that a blockage is forming, which makes it a good time to act.
Grease and Food Build-Up
Fat from pans and plates cools as it goes down the plughole. It sticks to the inside of the trap and waste pipe, and tiny bits of food catch on it. Over weeks, this layer grows and the water slows.
Coffee grounds, rice, pasta and starchy water can add to the problem. Even if you scrape plates, small amounts slip through every day.
A waste disposal unit, if you have one, does not stop this. It breaks food into smaller pieces, but those pieces can still settle in the pipe, especially when mixed with fat.
Shared Waste From Appliances
Many kitchen sinks share a waste pipe with a dishwasher or washing machine. Lint, food and detergent residue from these appliances can collect in the same pipe.
If the sink gurgles or fills up when an appliance is draining, the shared section may be partly blocked. This does not necessarily mean the appliance is faulty, but it may require investigation of the pipe they share.
A blocked air admittance valve or vent can also make water drain slowly and noisily, as the pipe struggles to let air in behind the water.
Fitting and Layout Issues
Waste pipes need a steady fall so water runs away naturally. A pipe that is too flat, sags in the middle or has too many bends can let waste settle. This tends to cause slow drainage that returns again and again.
Sometimes the problem is not the sink at all. If other fittings in the house are also slow, the blockage could be in the main drain, which is a different job.
What to Avoid and When to Get Help
It is tempting to reach for a strong drain cleaner. These can be harsh on skin, eyes and some pipework, and mixing products can give off dangerous fumes. Pouring boiling water into plastic waste pipes is also a bad idea, as it can soften joints.
Simple care helps. Use a sink strainer, wipe greasy pans before washing them, and let fat set before putting it in the bin.
If the sink stays slow, keeps getting worse, or water starts to sit in the bowl, it may be time for a professional look. Our blocked sink service in Oxford can check the trap and waste pipe, clear the build-up and let you know if anything in the pipework layout is making it worse.