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Why is my sink not draining?
Updated 07/26
By: Laura Macdonald
Reviewed: Content Team
A kitchen or bathroom sink not draining is one of those little problems in your home that you might notice and not deal with until it gets so bad you can’t use your sink. Make today the day you fix the problem with our guide to causes and solutions for why your sink isn’t draining. We’ll look at the
A sink that drains slowly, or not at all, is one of those problems that's easy to ignore right up until you can't use the sink at all. The good news is the most common causes are straightforward to identify and, in many cases, fix yourself.
The most common causes for kitchen and bathroom sinks
Seven ways to try clearing it yourself
Which methods actually work, and which are more myth than fix
A safety point worth knowing before mixing anything down the drain
Roughly what it costs to call a plumber
When it's time to stop DIYing and get help
Find a plumber near you
4 common reasons for a sink not draining
1. Food waste blockages
The most common culprit in a kitchen sink. Small bits of food go down the plughole daily, and rice, pasta, butter, and fats are particularly prone to building up into a genuine blockage over time.
2. Build-up of soap
Like fats, soap residue narrows the space water passes through inside the pipe, gradually restricting flow until the sink stops draining properly.
3. Foreign objects
Cotton wool, kitchen towel, small plastic items, broken glass, and food wrappers are common culprits that end up restricting or blocking a pipe.
4. Matted hair
The classic cause of a slow bathroom sink, hair builds up and tangles over time from washing, shaving, or clipping, eventually forming a solid blockage.
Why is my bathroom sink not draining?
Beyond hair, common causes include soap scum build-up, small objects stuck in the pipe, poor plumbing installation, or a blocked drain further down the system, sometimes caused by heavy rainfall, where the sink won't drain but the visible pipework looks clear.
Why is my kitchen sink not draining?
Alongside food waste, common causes include plastic wrapping caught in the pipe, butter, fat, or soap scum build-up, and occasionally damaged pipework itself.
If it's specifically your bath that's slow to drain rather than a sink, our guide on unblocking a bath drain covers that directly.
7 ways to unblock a sink that's not draining
The best method depends on the cause, so it's worth trying a few in order.
1. Use the waste disposal (if you have one)
Run it first and check it's actually working properly. A build-up inside an unused disposal unit can itself cause a small blockage.
2. Pour boiling water down the sink
Effective against fat-based blockages specifically. Pour it slowly, let it sit for 1-2 minutes, then run the hot tap to help clear the softened fat through.
3. Baking soda and vinegar
A commonly recommended home remedy, though it's worth setting expectations honestly: the fizzing reaction is fairly gentle and works best on light residue or odours rather than a solid, established blockage. Clear any standing water first, pour in a cup of baking soda followed by a cup of vinegar, put the plug in while it fizzes, then flush with hot water after a few minutes.
4. Baking soda and salt
Similarly gentle: mix a cup of baking soda with a cup of salt, pour it down the drain, leave for a few hours, then flush with hot water. Better suited to maintenance than a genuine clog.
5. Use a plunger
Often the most effective DIY method for a real blockage, especially with standing water present. Cover the drain hole completely and plunge firmly and repeatedly until the water recedes.
6. Insert a pipe snake
For persistent blockages that resist plunging. A flexible cable bends through the pipe to physically break up the clog; move it up and down once inserted, then flush with hot water.
7. Sink unblocking products
Chemical drain cleaners can be effective, but follow the manufacturer's instructions closely and always flush with water afterwards.
Never plunge a sink immediately after using a chemical drain unblocker. Residual chemical can splash back up at you during plunging. Flush thoroughly with water first, and leave it a while before trying a plunger if the chemical hasn't fully cleared it.
How much does it cost to unblock a sink not draining?
On Checkatrade, you'll only find trades who meet our high standards and pass up to 12 checks.
Cost depends on the cause and how accessible the blockage is. Our plumber cost guide has current hourly rates.
Plumber costs in the UK: 2026 price guide
Whether you are planning an exciting renovation or have a troublesome issue, our plumber cost guide contains daily, hourly and emergency rates.
If the blockage turns out to be part of a bigger problem, such as damaged pipework needing a full sink and tap replacement, our kitchen sink and taps installation cost guide is a useful next reference.
Before you call a plumber
Find a local tradesperson
Find a plumber near you
FAQs
It can help with light residue and odours, but it's not a strong degreaser or hair-dissolver. For an established blockage, boiling water, a plunger, or a pipe snake are generally more effective.
Not immediately after each other. Chemical residue can splash back during plunging. Flush thoroughly with water first and allow time before switching methods.
This usually points to a partial blockage, gradual soap or fat build-up, or hair caught partway down the pipe, rather than a full clog.
If none of the DIY methods clear it, if the problem affects multiple fixtures at once, or if you suspect damaged pipework, it's time to call a plumber rather than keep trying.
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