Kitchen sink unblocking, including grease and food waste

Where kitchen drains get blocked

A kitchen sink waste pipe is usually 40 millimetres in diameter: wider than a washbasin's, but much narrower than a toilet's. Directly under the sink bowl is the trap, often with a connection for the dishwasher and sometimes for the washing machine as well. From there, the pipe runs to the soil stack or the underground drain. Dirt can collect at any of these points, but not all at the same rate.

Grease setting in a cold pipe

Frying fat, cooking fat and oil usually go down the sink while they're still warm. As soon as they cool in the pipe, which happens quickly in a pipe running along an outside wall or through a cold crawl space, they solidify. A greasy layer forms on the pipe wall and grows thicker as soap residue and food particles stick to it. The grease acts like a net, and over time only a narrow channel is left.

Food scraps and coffee grounds

Rice, pasta, potato peelings and coffee grounds don't dissolve in water. They sink to the lowest point of the trap or a bend and combine with the grease to form a solid blockage. A strainer in the plughole catches most of it, but plenty of kitchens don't have one.

Long pipes under a kitchen island

With a kitchen island, the waste pipe runs a fair way horizontally under the floor before joining the rest of the system. The fall is often limited, and because there's no vent through the roof, there's often an air admittance valve under the sink. The longer and flatter the route, the more chance grease has to settle. In blocks of flats, where kitchens stacked one above the other all drain into the same pipe, we often find the blockage in the bottom section.

Blocked kitchen drain: the warning signs

A kitchen blockage usually gives you some warning. First the water drains more slowly, then the sink starts glugging when the dishwasher pumps out, and one day a layer of water is left standing in the bowl. A rancid smell from the plughole points to grease and food scraps going off in the trap. The sooner you act, the easier it usually is to unblock the sink.

You can often work out for yourself where the blockage is. If you have a double sink and the water is standing in only one bowl, the blockage is in the short section of pipe before the two bowls join. If both bowls are full and the dishwasher won't pump out, the blockage is further along in the shared waste pipe. And if the neighbours above or below you are having problems too, the blockage is in a pipe you share with them.

If the dishwasher's drain is blocked, the cause often isn't the appliance itself but the point where its drain hose connects to the trap under the sink. The same grease that narrows the rest of the kitchen drain builds up there. Clean the filter in the machine first. If water is still left standing, the problem is probably in the drain.

Unblocking a kitchen sink yourself: what's safe to try

You can often clear a kitchen blockage yourself in its early stages, as long as you go about it carefully.

Removing the trap

Put a bucket under the trap and have a cloth ready. Undo the nuts by hand or, with a bottle trap, just unscrew the bottom section. Clean the parts in a bucket of warm water rather than under the kitchen tap: without the trap in place, that water would run straight into the cupboard. Check that the rubber washer is still in good condition too. Reassemble everything hand-tight, then run the tap to check for drips.

Plunger and hot water

If cleaning the trap doesn't help, try a plunger. With a double sink, seal the other plughole with a plug or a wet cloth, otherwise the pressure will escape through it. Hot but not boiling water with a generous squirt of washing-up liquid can soften a grease blockage close to the trap. The well-known home remedy of baking soda and vinegar mainly produces a lot of foam; it does no harm in a slightly dirty trap, but it won't dissolve a solid grease blockage.

Why caustic drain cleaners are a bad idea

Caustic soda drain cleaners break down some of the grease, but only where they come into contact with it. They can't reach a blockage a few metres further along. The chemical is then left sitting in the trap, where it gradually damages rubber seals and splashes up as soon as you use a plunger. It's also a risk for the engineer who comes out afterwards.

When to call us

Stop and give us a call if:

• water is still standing in the sink after you've cleaned the trap;
• the dishwasher or washing machine pumps water back up into the sink;
• your neighbours are having drain problems at the same time;
• the problem comes back within a few weeks.

How we unblock a kitchen sink: drain snake and jetting

The engineer starts with the trap and the dishwasher connection, because that's where a lot of blockages are. If those are clear, the engineer goes into the pipe with a hand-held drain snake or, over longer distances, the electric drain machine. That clears a way through.

With grease, though, that isn't enough on its own. A drain snake pokes a hole through the blockage, but the greasy layer on the pipe wall stays put and soon traps new dirt. That's why, when a kitchen waste pipe has heavy deposits, we follow up with high-pressure jetting all the way to the soil stack or underground drain. In a commercial kitchen or a kitchen island with a long waste pipe in particular, the pipe then stays clear for much longer than if we'd only punched through the blockage. Find out more about this technique on our sewer cleaning page.

If the washbasin in the bathroom is draining slowly too, we'll sort that out on the same visit. Our page on washbasin unblocking explains what usually causes problems there.

Costs and help outside office hours

Unblocking a kitchen sink costs from €129. The call-out charge is not included and comes on top. If you need help late in the evening, at night, at the weekend or on a public holiday, the out-of-hours rate applies. If you'd like a thorough high-pressure clean of a long waste pipe, or regular maintenance for a commercial kitchen, you can ask for a quote. You'll always get a price estimate in advance.

A sink full of water on a Friday evening, with a dishwasher full of dirty plates and guests on the way, doesn't have to wait until Monday. We answer the phone outside office hours too, and the engineer is usually with you within the hour. In the meantime, don't use any water in the kitchen and switch off the dishwasher and washing machine.

Keeping on top of grease

A few habits will prevent most kitchen blockages:

• pour frying and cooking fat into a jar or old bottle, seal it and put it in the general waste;
• wipe greasy pans and plates with kitchen roll before they go into the sink or dishwasher;
• put a strainer in the plughole and empty it into the food and garden waste bin;
• clean the dishwasher filter regularly;
• run the hot tap for a moment after washing up.

If you have a kitchen island or a long horizontal waste pipe, preventive high-pressure jetting can be worthwhile, especially if you cook a lot.

Areas we cover and related services

We unblock kitchen sinks in places such as Utrecht, Breda, Nijmegen and Haarlem. Our service area page lists more cities with local information, but we're happy to come out beyond them too. To find out how we deal with blockages elsewhere in the house, see the page about our work as a drain unblocking company.

Water standing in your sink right now? Call 085 333 4698 and we'll talk through what's needed straight away.