Kitchen sinks are prone to blockages, along with most household drains - and they’re pretty much inevitable at some point.
Food waste, debris and minerals from the water can combine into a hardened sludge that blocks the U-bend under the sink, also known as “the trap”. Once the trap is blocked, water won’t be able to drain properly and may even regurgitate back into the sink.
However, not all blockages occur in the trap, but this is the most likely scenario.
This is a guide to unblocking a kitchen sink.
Causes of a blocked sink
1: Food and debris
A blocked sink is likely caused by food particles, especially those that don’t easily absorb water and degrade.
Some prime culprits include burnt food from frying pans, coffee grounds, cooking fat, butter, egg shells, pasta and rice. However, putting any quantity of hard food down the kitchen sink can block it, so that’s best avoided unless you have a disposal unit under the sink (rare in the UK).
If you live in a hard water area, minerals from your water might worsen your chances of a blocked sink.
If this is the case, your sink might regurgitate nasty discoloured water when you use it, indicating that the U-bend is backed up.
2: A blockage somewhere nearer the drain
In most situations, a kitchen sink blockage is local to the sink itself. However, there could be a blockage somewhere else down the pipes. If this is the case, you may also find that other units connected to the mains water, like a dishwasher, are also blocked or flooding.
If you attempt the following fixes, but your sink is still showing signs of an issue, it’s sensible to call one of our plumbers,
Ways of unblocking a sink
Luckily, most blocked kitchen sinks are straightforward to fix, requiring little to no DIY or plumbing experience.
If you have a waste disposal unit
Some sinks are equipped with an electric waste disposal unit that connects to the plughole. When you flush food waste down the sink, the disposal unit will grind it into a fine paste and eject it down the drain with the wastewater.
These are more common in the USA, but some UK sinks will have one. If you notice a large electrical unit connected underneath your sink, then this is probably a waste disposal unit.
If you have one of these and your sink blocks, the first protocol is to check the unit (as the unit is specifically designed to ensure your sink never blocks). In this situation, disconnect the unit from the mains and manually twist the blades (there should be a way to do this with an Allen key).
Never attempt this without disconnecting the unit from the mains. You can disconnect the unit and unblock it if that doesn't work.
1: Boiling water
Firstly, start by pouring boiling water down the sinkhole. Next, boil the kettle, remove the strainer if possible, and pour the boiling water down.
Pour from a decent height - this will increase the velocity of the water and apply more pressure to the drainage. Be careful not to burn your fingers or hands!
2: Baking soda and vinegar
Pour a small cup of baking soda down the sink and follow up with a cup of vinegar. If needed, you can use a funnel to direct the baking soda into the sink.
Once you pour the vinegar in, put the sink stopper on and hold it down gently. The reaction between the vinegar and baking soda should push downwards, forcing the blockage to break down.
If the force pushing upwards remains strong, release the sink stopper. This might take a few minutes. Afterwards, run the hot tap or follow up with more boiling water.
- Remove water from the bowl.
- Pour or funnel baking soda into the sinkhole with the strainer removed.
- Add one cup of white vinegar.
- Cover the sinkhole with the stopper.
- Wait for 5 to 15 minutes until bubbling subsides.
- Remove the stopper and run the hot tap or pour boiling water down the sinkhole.
3: Soda crystals or washing powder
Soda crystals are an all-purpose cleaning product which is excellent for unblocking sinks. If you don’t have any, try biological washing powder instead.
Add a mug full of powder to the sinkhole with a mug or two of hot water. The mixture should bubble up - follow it up with hot or boiling water.
4: Use a wire
You can use a wire or an untwisted coat hanger to force the sinkhole down, sensing the blockage and prodding it to release the debris.
A plumber’s snake takes this to the next level, but we recommend trying a plunger before that.
5: Sink plunger
If all steps have failed so far, your drain might be even more blocked than before! However, it’s still worth trying the quick fixes first.
The next method is to use a small sink plunger. These draw water from the basin and force it towards the drain at high pressure.
If you don’t own a plunger, you can fill a 2-litre bottle, direct it over the sinkhole and squeeze it to force the water out quickly.
- Partially fill the sink with hot water
- Push the plunger over the sinkhole to seal it
- Pump the plunger
6: Plumber snake
A plumber's snake is similar to using a wire but essentially allows you to drill into the blockage and dislodge it.
Simple plumber snakes are pretty easy to use, but there’s little point in trying this unless you know the sink is blocked near the U-bend.
7: Sink unblocker
You can purchase purpose-made sink unblocking products.
Make sure you choose one suitable for kitchen sinks - this won’t be a ‘drain cleaner’ - as that would probably melt the pipes.
8: Remove and clean the U-Bend
If all else fails, the only option remaining is removing the U-bend, aka. the trap. Place a bucket underneath the U-bend and, with gloves, if you prefer, carefully unscrew the two connectors and remove the U-bend.
With any luck, the U-bend will be clogged with gunge. Remove the gunge by flushing the U-bend and prying out any solidified debris with a wire.
Then, re-fit the U-bend. You can use PTFE plumbing tape to seal the joint if it’s leaking.
When to call us?
If the blockage isn’t in the U-bend and none of these other techniques works, the blockage may be located further down the pipe.
In that case, you can keep trying to unblock the sink using a combination of these techniques, but if nothing works, it’s wise to give us a call. Our plumbers will safely remove a blockage from further down the pipe without running the risk of damage. Wether you have blockages in your shower drain, kitchen sink or out door drains we can help solve the problem. We also have annual policies which cover all types of drain problems.
Will bleach unblock a sink?
Bleach probably won’t break down the debris blocking your sink, but it’s worth a go. Add ⅕ to ½ a small cup of bleach to your sink and flush it with plenty of warm water.
Can Coke unclog a drain?
Coke contains phosphoric acid and is reasonably caustic, so it could work in theory. However, using baking soda and vinegar is a cheaper option than using coke to unblock a sink or drain!
Coke is likely not strong enough to dissolve stubborn blockages.
How do you unblock a sink naturally?
Plungers use water only, so they are probably the friendliest way to unblock a sink or drain. Using a wire or plumber’s snake is also natural and environmentally friendly.