Kitchen blockages build differently from bathroom ones
A kitchen sink deals with grease, cooking oils, tiny food particles and detergent. Warm fat can travel some distance before cooling and sticking to the inside of the pipe. Over time, that narrowing catches more debris until the sink begins to empty slowly or stops altogether. Coffee grounds, rice and fibrous scraps can make matters worse. If a dishwasher or washing machine shares the same waste, the first sign may be dirty water backing up into the sink when the appliance pumps out.
Work out whether the trap is the problem
If the sink is completely blocked but other fixtures drain normally, the trap or nearby pipe is a sensible first suspect. A bottle trap or tubular trap can hold food debris and congealed grease. If it is accessible, it can often be removed for cleaning once a bowl is placed underneath. If the trap is clean but the sink still will not drain, the obstruction lies further along. Reassembling plastic joints squarely matters; a cleared blockage is not much help if the trap starts leaking afterwards.
Be cautious with chemical cleaners
Strong drain chemicals are often disappointing on dense grease and can remain trapped in standing water. They also create a hazard for anyone who later opens the pipe. Never mix different drain products, bleach or acids. Boiling water is not suitable for every waste system either, particularly where plastic fittings may be stressed by extreme heat. A plunger or mechanical cleaning method is usually easier to control. If you have already used chemicals, tell the person attending before they dismantle anything.
Signs that the obstruction is beyond the kitchen
A blocked sink combined with a slow outside gully, toilet problems or water backing up elsewhere suggests the issue may be in a shared drain. The same applies if plunging one fixture causes water to appear in another. In that situation, repeatedly dismantling the kitchen trap is unlikely to solve the underlying problem. Check accessible outside drainage points without removing heavy covers or putting your hands into waste water. If more than one household is affected, the responsibility for the blocked section may also need to be established.
What a professional may do
A plumber can clear local waste pipework and check whether the kitchen installation itself encourages grease to settle. Long horizontal runs, poor falls and too many tight bends make recurring blockages more likely. Where the restriction is in the underground drain, a drainage specialist may use rodding or high-pressure equipment. If blockages keep returning, a camera inspection can sometimes show displaced joints, scale or another defect. The right response depends on where the blockage sits, not simply on how much water is in the sink.
How to describe the problem clearly
Tell the contractor whether the sink is completely blocked or just slow, whether a dishwasher shares the waste and whether outside drains are behaving normally. Mention any recent kitchen work because a new waste arrangement can expose problems with fall or venting. If the sink has blocked before, say how often. Photographs under the sink can show the trap and pipe route, while a short video of water backing up can be useful. A good description helps the contractor arrive with the right equipment rather than treating every blocked sink as identical.
Preventing the same kitchen blockage returning
Once the sink is clear, small changes can reduce the chance of another grease blockage. Wipe fatty pans with kitchen paper before washing them, use the sink strainer and put coffee grounds and food scraps in the bin rather than the waste. If a dishwasher shares the pipe, check that its discharge hose is connected correctly and that the waste does not back up when the pump runs. Where the pipe route is poor, however, household habits may not be the whole story. Ask the plumber if the fall and diameter of the waste are sensible for the length of the run. A kitchen that has blocked repeatedly since a refurbishment may need the arrangement correcting rather than ever stronger drain cleaner.
This page is general guidance about blocked kitchen sink; the cause in an individual home still needs to be established from the actual installation.