How to unblock a sink.

So you have a blocked sink.

Chances are you are scouring the internet for that miracle bottle of drain unblocker or the latest tool to have a go yourself.

Take a moment to read this blog and it could save you a lot of time, money and effort….

blocked sink causes and remedies.

Blocked sinks are usually caused by one of the following…

Grease Build Up.

F.O.G – Or Fats oils and grease. Accumulate in your waste pipes and traps and are the main cause of a blocked sink.

As the F.O.G is washed through the plug hole it cools and solidifies into a hard congealed mess within the waste pipe. Which in turn builds up and eventually stops the flow of any waste water.

In a domestic setting these F.O.G’s can be kept at bay with regular maintenance and cleaning. And the use of products such as enzyme sticks.

But most blockages of this nature will probably need a thorough clean by a drainage company to fix properly.

Commercial kitchens should be using grease traps in combination with the above. And may require more frequent drain maintenance or grease management. For more info visit Grease management for commercial drains UK.

Hair both Human or pet.

Hair down the plug hole. Every house hold has more than likely encountered this problem.

The simply answer is to use plug hole strainers and empty trap fittings on a regular basis.

House hold cleaning liquids can be purchased purely for this problem also.

If the blockage is a little more sinister or further downstream than you can reach, then professional help is needed from a blocked drain company.

This needs to be unblocked using rotary mechanical equipment. Or high pressure drain cleaning equipment.

Image of a blocked sink being cleared. 4 Drains.
Other common blocked sink reasons.

The main two reasons above are not exclusive. Blocked sinks can be for a number of reasons for example –

Coffee grounds, food parts washed away or from a waste disposal unit, Foreign objects being lost, maybe its a connecting blocked drain, or a venting issue restricting the flow. The list is endless.

Unblocking Your sink.

Most people are going to want to have a go them self before calling in a drain company. And if its a case of just removing and clearing a trap or giving the sink a quick plunge then that is great for some one that is capable of doing so.

However there are instances where calling a drain company would save time, money and the use of staff etc. This is explained here.

So here is your basic step by step of how to clear a blocked sink.

Checking waste traps.

If a sink is slow running and not quite as it should be. The first thing to do is to remove the trap under the sink. This trap is designed to catch and hold any entered debris before it reaches your wastepipes or drains.

By placing a small bucket or container under the trap it can be unscrewed anti clockwise and emptied out. Being careful not to lose any washers or disturb other fittings.

Once clear and put back as found, the tap can be run slowly to check the blockage has gone and the waste water is not backing up or slow to run away.

At this point double check the seals for any leaks around the trap and re seat if needed.


A lot of people struggle with plungers. mainly because they use the wrong type or size of plunger, or they struggle to maintain an adequate seal when plunging.

The best sink plungers are the concertina style sink plungers. As apposed to force cups because they can apply more plunging pressure when used.

The trick is to place the plunger over the plug hole and use the water as a hammer in an up and down motion to force away the blockage.

This may require covering the overflow outlet at the same time using a wet cloth. This prevents the lose of suction and stops waste water coming out and making a mess.

Sink plunger
Image of a sink plunger as mentioned above.
Sani snakes.

Sani snakes that are purchased at a hardware store are basically a small hand held wire that can be pushed into a wastepipe in an effort to dislodge a blockage.

These are only any good for soft blockages and are very restricted by the length needed to reach the blockage.

They can be hard to be manoeuvred through the pipe or into a solid blockage. This is due to them being hand powered and very flimsy.

Professional Tools.

Professional tools are very expensive to purchase and maintain. If the above methods have been exhausted then calling in a drain company is the best option.

They will carry a variety of different tools for every scenario. For example for removing a flushed foreign object or fixing a connecting blocked drain.

These would normally include tools such as wet vacs, mechanical rotary drills, milling machines, extraction tools, high pressure drain jetting equipment, drain CCTV units and more.

4 Drains Vanpack image. copyright
An example image of one of the drain jetters used by 4 Drains.

Chemicals & Caustic liquids.

Most caustic liquids are now prohibited to be purchased due to new UK laws concerning their misuse by a stupid minority.

Acids for example which have been used to clear blockages in the past can actually cause more harm than good.

Because they are produced at such high potency levels they can burn through rubber wastepipe seals, tarnish stainless steel sinks and are obviously very dangerous if used in the wrong way.

They can cause serious burns, blindness and also effect your breathing if used incorrectly as they can produce a gas if mixed with certain household bleaches or cleaners.

wastepipe and drain blockages.

Most sinks are connected to a plastic wastepipe of between 1.5″ and 2″ diameter. With the exception of wash basins that may have smaller 1.1/4″ pipes.

From here the wastepipe will normally connect to either a drain line, Soil Stack, gully or grease trap. If the blockage is in any of these, then more than likely professional assistance will be needed.

If our services for blocked drains, blocked toilets, blocked sinks, drain CCTV, maintenance are needed and you live in the southeast of England (UK) Please contact our staff and we will be happy to help.

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