How To Unblock a Sink – What Works & What Not To Use
The bottle of caustic gel under the sink is the first thing most people reach for, and it’s very often the thing that turns a twenty-minute job into a new waste pipe and a ruined kitchen unit.
We’re not being purist about this. There’s a proper order to unblocking a sink, and chemicals are near the bottom of it.
What actually works on a blocked sink?
Start with a plunger, then take the trap off and clean it. That clears most blocked sinks in most houses.
The plunger. Cover the overflow with a wet cloth first, or you’ll just push air out of the hole instead of pressure down the pipe. Get a decent seal over the plughole and use short, firm pushes rather than one enormous heave.
The trap. This is the U-bend or bottle trap under the sink, and it’s where the blockage usually is. Put a washing-up bowl underneath, unscrew it by hand, and empty it out. On a kitchen sink you’ll often find a grey plug of solidified fat. On a basin it’ll be hair and soap. Rinse it properly, check the washers are seated, and screw it back finger-tight plus a nudge.
A plughole tool or hair grabber. For hair sitting in the first stretch of waste beyond the trap. These are the flexible plastic strips with barbs on, a couple of quid, and they’re horrifying but effective. Some places sell them as a drain snake, which is the same idea, but it isn’t the first thing we’d buy.
Enzyme cleaners. Useful for keeping a slow-running waste healthy over weeks. Useless when there’s already standing water, because they need to flow through to work.
What wrecks your pipes?
A few things, and they’re common enough that we see the results regularly.
Caustic gel poured into a fully blocked sink. The product can’t drain away, so it sits directly on the blockage and on the plastic around it, generating heat. Plastic waste fittings and their seals do not enjoy this. We’ve opened traps that were soft and deformed.
Mixing products. Chemical unblockers and bleach together can produce genuinely dangerous gas in a small bathroom. Don’t combine anything, and don’t add a second product because the first one didn’t work.
Kettles of boiling water into plastic waste. Hot water helps with fat. Boiling water repeatedly poured into PVC waste doesn’t do it any favours. Hot from the tap, or a kettle left to stand for a couple of minutes, is plenty.
Wire coat hangers. They scratch the inside of the pipe, which gives future grease something to cling to, and they usually just ram the blockage further along where you can’t reach it.
Caustic products into a septic tank. They kill the bacteria the tank depends on. If you’re not on mains drainage, this matters.
There’s a bigger problem with chemicals even when they appear to work. They tend to burn a pin-hole straight through a fat blockage. Water drains again, so you assume it’s sorted, but the pipe lining is still coated. It blocks again in a few weeks, sometimes with a softened joint that then starts to leak. That’s how a trap clean turns into a ripped-out waste and a swollen cabinet base.
What causes a blocked kitchen or bathroom sink?
In kitchens it’s fat, cooking oil and starchy food waste. Fat goes down warm and liquid, then cools and sets on the pipe wall a millimetre at a time. Pasta and rice water adds starch to that.
In bathrooms it’s hair bound together with soap scum, which builds into a surprisingly solid mat.
Wipes, cotton buds and small toys don’t dissolve and never will.
One that catches people out: the gully outside the kitchen wall. If that’s silted up with fat, the sink can back up or smell even though the trap under the sink is spotless. Worth a look, especially on older properties around Hinckley and Barwell where the gully has been sitting under a bush for a decade.
How do I unblock a sink without chemicals?
Plunge it with the overflow covered, then take the trap off over a bowl and clean it out by hand.
That’s the method. If you can’t get the trap off, or the water is sitting completely motionless with no movement at all, stop there. Don’t start adding products to see what happens, because it changes the job for whoever comes next.
Are chemical sink unblockers safe?
Not as a first step, and not at all when the water isn’t moving.
If you have already used one, tell us when you ring. It genuinely matters. We need to know before we open a waste up over our hands, and it changes how we approach it.
When should I call you?
Give us a ring if:
- the water won’t move at all
- it clears and comes back within days
- the bath or the toilet is affected as well
- there’s a sewage smell alongside it
- chemicals have already gone down
Several fittings running slow at once usually means the problem is past the individual sink, further along the shared waste or the stack.
We clear and refit traps and waste pipework as plumbing work right across Hinckley, Burbage, Leicester, Nuneaton and Coventry. If the fault turns out to be in the underground drain, we’ll assess it and tell you straight that you need a drainage contractor. We’re not going to sell you another bottle of something.
Waiting is how kitchen floors and unit carcasses get soaked, and neither of those is a cheap fix.