If your kitchen sink keeps blocking again and again, the problem is probably not at the plughole. A plunger or a hot flush may clear it for a few days, then it comes back, because the real build-up is further down the pipe. Warm cooking fat goes down the sink as a liquid, cools inside the pipe, and sticks to the walls. Food scraps and starchy waste then catch in that sticky layer, and the opening narrows a little more each time. This guide shows where the blockage is, the safe checks, the cost, and when to stop.
Find your pattern first
Find the line that matches your sink, then go to that section.
- Only the kitchen sink is slow, and it clears for a few days then blocks again: the build-up is in the trap or the kitchen waste run. Go to the causes table.
- The sink backs up when the dishwasher empties: the kitchen waste run is restricted. Go to the safe checks.
- The sink gurgles, or other drains are slow too: the problem may be further down, in a shared drain. Go to how to tell where the blockage is.
- Water is coming back up, or an outside drain is full: stop and call. Go to when to stop and call.
- You just want the cost: go to what a proper clear costs.
Why grease keeps coming back
Grease is the one kitchen waste that changes state inside your pipes. Fat from a frying pan, a roasting tray or a creamy sauce looks harmless when it is hot and runny. Once it reaches the cooler pipework under the sink and beyond, it thickens and clings to the pipe wall, especially at bends, joints and any section where the fall is slight.
That sticky lining is the real problem. Every plate rinsed afterwards adds something for it to catch: rice, pasta, peelings, coffee grounds and crumbs. Layer by layer, the opening shrinks until normal washing-up cannot get through. Clearing only the plughole leaves most of that lining in place, so the sink blocks again.
Hot water does not solve this on its own. It may melt the nearest grease, but it can also carry that grease further down the pipe, where it cools and sticks again. That is why a sink that seems fixed after a hot flush can block again a week later. Yorkshire Water’s sewerage guide puts it plainly: do not wash leftover fat, oil or greasy sauces down the sink, because fat can solidify in your pipes like a block of lard. Let it cool, pour it into a suitable container and put it in the bin, and wipe pans with kitchen roll before washing up. Dishwashers do not remove the risk either, because they discharge warm, greasy water into the same kitchen waste run.
What is actually blocking your sink?
| Cause | What you will notice | Safe yourself, or engineer job |
|---|---|---|
| Grease further down the waste pipe | Slow draining that returns after a clear; worse after heavy cooking | Engineer job: beyond the trap, needs proper clearing |
| Grease and food in the trap | Kitchen sink only slow; sometimes a sour smell | Safe yourself only if confident: bucket underneath, never force a seized trap |
| Food waste, starch and coffee grounds | Blockage after rinsing plates or pasta water down the sink | Safe yourself: stop rinsing those down the sink |
| Dishwasher waste connection restricted | Sink fills or gurgles when the dishwasher empties | Safe yourself: check filter and hose kink only |
| Poor fall, sag or damaged pipe | Same sink blocks again even with careful use | Engineer job: needs inspection, possibly a camera survey |
| Shared or outside drain blocked | More than one drain slow, or water at an outside drain | Engineer job: do not lift heavy manhole covers yourself |
The key question is not whether the sink is blocked, but whether the same sink blocks again after a careful clear. A one-off blockage after a large meal is usually local. A pattern of blocking, clearing and blocking again points further down the pipe.
Safe checks, in order
Work through these in order, and stop at the first one that explains the problem. Do not use chemical drain cleaners repeatedly, and do not keep forcing a plunger at a blockage that will not move.
- Check the plughole and strainer. Lift out any strainer and clear food and hair you can reach. A clogged strainer can look exactly like a blocked pipe.
- Try a plunger, properly. Use a cup plunger, with enough water in the bowl to cover the cup. Seal the overflow if there is one, and plunge firmly but steadily. If the water moves and then slows again within days, that points to a deeper restriction.
- Try hot water with washing-up liquid, once. A bowl of hot water with a squeeze of washing-up liquid can loosen a minor, local grease film. Do not pour boiling water down repeatedly, and do not expect it to clear a deep deposit.
- Check the trap, only if you are confident. Put a bucket underneath, loosen the trap by hand, and clear what is inside. If a joint is seized or you cannot refit it tightly, stop and leave it for an engineer.
- Run the dishwasher test. Empty the sink, then run the dishwasher on a short cycle and watch the sink. If water backs up as the dishwasher empties, the kitchen waste run is restricted beyond the trap.
- Write down the pattern. Note when it blocks, what was cooked just before, whether the dishwasher was running, and whether any other drain was slow. That pattern helps an engineer find the real cause instead of clearing the same spot again.
Our guide to blocked drains in Bradford covers the wider case, including outside drains and when a blockage stops being a kitchen job.
How to tell where the blockage is
Use the clues together: a single slow sink usually means a local problem, while several clues together point further down.
| What you notice | Where the problem probably is | What to do |
|---|---|---|
| Kitchen sink only, slow or blocked | Trap or kitchen waste run | Safe checks above; call if it returns |
| Sink backs up when the dishwasher empties | Kitchen waste run or dishwasher connection | Check the dishwasher filter; call if the run is restricted |
| Gurgling from the sink or other plug holes | Air trapped by a restriction further down | Note which fixtures gurgle; call if it keeps happening |
| More than one drain slow at the same time | Shared drain or outside drain | Stop DIY clearing; this is an engineer job |
| Water rising in an outside drain, or a sewage smell outside | Outside or shared sewer | Do not work on it yourself; keep children and pets away from standing water |
WaterSafe makes the same distinction: if only one fixture is affected, the problem may be confined to the internal plumbing, but if multiple fixtures are slow or gurgling, the blockage is likely in the outside drain. WaterSafe’s guide to telling if an outside drain is blocked explains those signs in more detail. If other drains are affected, a drainage service in Bradford can check the run properly rather than clearing the kitchen sink in isolation.
When to stop and call
Call an engineer if any of these apply: the sink blocks again within days or weeks of a clear; water backs up when the dishwasher runs; more than one drain is slow or gurgling; sewage is coming back up; an outside drain is full; the trap leaks after you have touched it; or you cannot find the cause from the checks above.
Do not lift heavy manhole covers, do not put your hands into a drain full of foul water, and do not keep using chemical cleaners on a blockage that will not clear. If you can smell gas, leave the property and call the National Gas Emergency line on 0800 111 999; gas work is for a Gas Safe registered engineer only, and never open a boiler casing. For a kitchen plumbing in Bradford visit, an engineer can clear the run properly and check whether the problem is grease, a damaged section or a shared drain. You can call Plumber Bradford Pros on 01274 041977.
What a proper clear costs
The figures below are UK guide averages, not this business’s prices. They come from Checkatrade’s drain unblocking cost guide, last updated October 2026. Prices depend on method and location, so a quote should say what is included.
| Job | UK guide average | Notes |
|---|---|---|
| Sink unblocking service | Around £60 | Local blockage close to the fitting |
| Drain rodding | Around £85 (£75 to £150) | Rods break up a blockage further along the pipe |
| High-pressure water jetting | Around £185 (£120 to £250) | Cleans grease from the pipe walls, not just a hole through it |
| Rodding and jetting combined | Around £270 (£180 to £400) | Common when rodding alone does not fully clear grease |
| Standard call-out | Around £60 | Check whether it is included in the total quote |
| Emergency call-out | Around £180 | Out-of-hours visits cost more than a standard call-out |
| Basic CCTV drain survey | Around £200 (£150 to £300) | Worth considering when the same sink keeps blocking |
For a recurring sink, the cheapest clear is not always the cheapest outcome. A quick clear that leaves the grease lining in place can mean paying again a month later. Jetting costs more than rodding, but it cleans the pipe walls, which matters when grease is the cause. If the same sink has blocked three times, a camera survey can be cheaper than a fourth clear that finds nothing. Always ask whether the call-out fee and VAT are included.
Why Bradford kitchens block again
Bradford’s older terraces and back-to-back houses shape this problem. Kitchens are often at the back of the house, with a longer waste run to the drain than in a newer home, giving warm grease more pipe to cool in. Pipework in these homes is often older, with more bends and joints where grease can catch, and in terraced streets the drains may be shared, so a problem further down can show up first in the kitchen sink.
Student lets add another pattern: several people cooking in the same kitchen, often with heavy, greasy cooking. A sink that coped with one household can start blocking again when the same kitchen serves four or five people. November makes it worse too: roast dinners put more fat down the sink when cold pipework makes grease set faster.
Prevention: keep grease out for good
- Scrape first, every time. Scrape plates, pans and trays into the bin or food waste caddy before they reach the sink. A sink strainer catches what is left.
- Jar the fat. Let cooking fat cool, pour it into a jar or tin, and bin it once set. Wipe the pan with kitchen roll before washing up.
- Do not rinse starch and grounds down the sink. Pasta water, rice, potato peelings and coffee grounds all add bulk to a greasy lining. Bin them instead.
- Use hot water as maintenance, not as a cure. A regular hot flush with washing-up liquid can help a clean pipe stay clean. It will not clear a deep deposit, and it never replaces keeping fat out in the first place.
- Scrape before the dishwasher too. The dishwasher discharges into the same waste run, so what goes into it ends up in the same pipe.
- Watch for the early signs. Water sitting longer, a faint gurgle after the dishwasher, or a sour smell from the plughole are all easier to deal with than a full blockage.
Frequently asked questions
Why does my kitchen sink keep blocking after I clear it?
Because the clear only dealt with part of the problem. If grease has built up further down the pipe, clearing the plughole leaves most of the lining in place, so new debris catches straight away and the sink blocks again.
Does hot water clear a grease blockage?
It can loosen a minor, local grease film, but it will not clear a deep deposit, and it can carry grease further down the pipe.
Should I use chemical drain cleaner on a recurring blockage?
No, not repeatedly. Chemical cleaners rarely shift a real grease deposit, they can damage fittings, and they make the job less safe for anyone who later works on the drain.
Why does my sink back up when the dishwasher runs?
Because the dishwasher discharges into the same kitchen waste run. If that run is narrowed by grease, the extra water has nowhere to go and backs up into the sink.
How do I know if the blockage is further down the pipe?
Look for a pattern: the same sink blocking again after a clear, gurgling from other plug holes, more than one drain slow at the same time, or water at an outside drain.
When is a camera survey worth it for a kitchen sink?
When the same sink has blocked several times, or clearing never lasts long. A camera survey, around £200 as a UK guide average, can find a sag or shared-drain problem that clearing alone will never fix.
Plumber Bradford Pros, 164 Dyson Street, Bradford BD9 4DE. Call 01274 041977.
