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What Are The Causes Of Blocked Drains

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  • Plumbing, Drainage, Toilet, Waste, Blockages
  • Posted date:
  • 05-09-2022
What Are The Causes Of Blocked Drains

What are the causes of blocked drains? This article looks at common causes of clogged drains and how to avoid blockages.

Every year, more homeowners experience blocked drains, kitchen sinks and toilets, with the most common causes being small items we flush down our drains daily. If you are suffering from drain blockages at your home, there may be some valid reasons why your drainage systems aren't working.

Why are my drains blocked?

Many foreign objects and food waste can be the cause of clogged drains in your bathrooms and kitchens. Drain specialists are accustomed to the many causes of blocked drains, from too much toilet paper being flushed to tree roots causing flooding in external drains and gutters.

If you have attempted using over-the-counter drain cleaner on your drain system when you notice gurgling noises or slow drainage, there could be more blocking it than you realise. Your plumbing system is intricate, with water flow being easily disrupted by cooking grease, paper towels and other things that are accidentally flushed down the toilet.

To avoid creating blockages and other drainage problems, let's look at some of the common causes of drain blockages and what objects could be obstructing water flow.

Common Causes Of Clogged Drains

What Are The Causes Of Blocked Drains

Due to the nature of your drainage system, with the many underground pipes required for efficient water flow, domestic properties can experience drain blockages from just about anywhere. 

While kitchen sinks can get clogged with food particles, tea leaves and cooking fat, your toilet can become clogged with human waste, paper towels, cotton wool and sanitary products. Sink drains have to experience soap scum, hair, oil and many other small objects, which can lead to a build-up.

If you notice clogged pipes and slow drainage in a particular area more than others, start monitoring what is being poured down those drain pipes. This can inform you of how you can make changes to prevent this from happening.

Here are the most common causes of clogged drains:


While the majority of UK homes don't have access to garbage disposals, you should not be tempted to substitute them for your kitchen sinks. 

Food bits and chunks should not be flushed, poured or washed down any home pipes or drains. 

This extends to showers, baths, kitchen sinks, and even garden drains! You should be protecting your plumbing system, and they are not designed to take large influxes of food waste. 

Food can be sticky, hard and sharp, which your water pipes have not been designed to handle. Small amounts of food may not seem like a problem, but if you do this on a regular basis, you will quickly experience clogged drains and foul smells coming from your sinks and pipes.


Hair is one of the most common culprits of blocked drains, from bathroom sinks to shower drain covers. 

When hair accumulates, it can block drains and create slow blockage (or total blockage in some cases). The best course of action to prevent a build-up of hair is to monitor where you're brushing your hair and check the plughole after showering. 

You don't need specialist equipment to remove hair from drains, and you can implement some simple preventative measures to stop your hair from clogging your home plumbing. 

Consider buying drain screens or cleaning your hair brush over the rubbish bin instead of the sink. You can catch hair in netting or a drain cover, emptying it into the bin after a shower.

Flushable wipes

Many face wipes and baby wipes are advertised as "flushable", giving homeowners the idea they will break down after being flushed down the toilet. 

However, many wipes are not flushable and are the cause of many blockages across the UK. They can get stuck in the pipes, cause broken pipes and flooding when flushed down the toilet. 

UK plumbing systems are not prepared for wipes, paper towels and mass amounts of thick toilet paper. When you do flush such things, you are testing the capabilities of a system that is designed to carry water and human waste.

Feminine hygiene products

Hygiene products that contain cotton and other fibres don't biodegrade as easily, meaning baby nappies and feminine products pose a serious risk to home plumbing systems. 

When you flush tampons, pads or even face wipes, cotton wool or dental floss down the toilet, you can cause a blockage. 

Due to their cotton nature, they will attract other clogging agents and materials, stopping the water flow. Most sewer treatments contain microorganisms to break down human waste, but they will not break down anything else - even if your feminine hygiene products are advertised as flushable.

Leaves and Outdoor Debris

Many homeowners will regularly clear blockages caused by leaves and nature, as sticks, dirt, and rocks collect around drains. 

Whether they come from your compost bin, garden or just excess dirt, a buildup of leaves is a regular problem for drainage services to deal with. While you want to clear your garden, you should keep your yard clear and not wash them down the storm sewer drain. 

Plants, roots and soil are efficient at clogging your pipes, even when you only deal with a few.


House plumbing and pipe systems can disintegrate over time, especially with clay, terracotta and concrete pipes. 

Older homes will suffer from this more as the joints and soil erode away, especially during colder temperatures. As the temperature drops to freezing in Winter, the continuous pressure can affect the pipes and freeze them over. 

Your pipes can begin to sag and cause water flow problems, potentially leading to blockages.

Slope of the sewer

The water and sewer pipes must have the correct slope angle; otherwise, the water flow will not be suitable, and there could be draining problems. 

This is a common problem among older houses where the pipes may have shifted over the years, but you can easily prevent this by getting professional help. 

As gravity is the driving force of most water systems, you must ensure the drainage pipe has a pitch of at least 1/4 inch per foot. To fix this, you will need specialist equipment and proper maintenance care from a plumber.

Combinations of materials

Another one of the most common causes of blocked drains is the build-up of various materials, forming a hard barrier water cannot pass through. 

Detergent and soap buildup is dangerous for plumbing systems as they can attract other debris and materials and create a clog in septic drain fields. 

Many laundry experts suggest using soaps that don't contain phosphates, as these are less likely to cause blockages. Soap-free washes can also help you stop blockages from forming in your bathroom.

Undersized sewer pipes

If your sewer pipes are undersized or not planned out correctly, this can lead to clogs and blockages. 

Of course, it's not easy to understand the complete plumbing history of a property, as many of these records are not common knowledge. However, if you have recently built an extension or modified your home to add more bathrooms, kitchens or sinks, you must've met the standard minimum for the size of the sewer drains. 

This should be four inches in diameter as a minimum, but depending on the plumber you use, you could have a slightly bigger one installed. You can also overload the system, even when this has been properly sized for your property. 

If your home is on a septic system and the waste capacity has grown, you could begin smelling foul smells or experiencing backups.

Pipe scale

As water moves throughout your system, mineral deposits are left on the inside of your pipes. 

Areas of hard water across the UK may experience this more, as the scale deposits are left from dissolved calcium and magnesium in the water. 

Small amounts of scale are not a problem and cannot be avoided, but as more begins to collect on the pipes (reacting to the changing temperature and wet conditions), these can easily form into small solid objects. 

Your washing machine and dishwasher can become affected and run less efficiently when scale builds up.

Foreign Objects

There are many other materials and objects that blockages are commonly caused by. From sanitary items, children's toys, jewellery, coffee grounds, dental floss and condoms, many things have been found lodged in drains and pipes. 

Excessive amounts of almost anything can cause a blockage, as our plumbing systems are not designed to handle anything other than water and human waste. Parents should take time to educate their children on what is allowed down a toilet and what isn't, or they will experience clogged drains.

Cat litter

Finally, cat litter is known for regularly causing issues and obstruction to pipes. 

Cat litter should not be flushed down the toilet or disposed of down a drain; instead, it should be thrown in the bin. This clay-based material can harden in your pipes, along with being sharp and cutting into the drainage system.


Leaks regularly cause blockages for plumbing systems, along with further complications. 

The soil can erode when the water is leaking underground, causing immense pressure on the pipes. From there, the pipes can drop, change position and sag. In extreme cases, the pipes can break and cause further flooding.

Fat, oil and grease

Drain cleaning services have to remove cooking oil, grease and fat from home plumbing systems more often than they'd like, with professional plumbers educating homeowners on what can and can't be poured down their kitchen drains. 

While many of us have gotten good at understanding what grease can do to our indoor and outdoor drainage, many people continue to pour vegetable oil, chocolate, butter, cream and more down their drains. Keeping a watchful eye on what you're pouring down the drains will save you time and money, as you should be extra careful with any oil and grease. 

They can easily solidify and congeal, binding substances together and blocking your drains. To stop this particular problem from happening, you should throw away your oil and grease in sealed containers and then add them to your general house rubbish.

Although tree roots do typically affect older homes more than modern ones, they are one of the main causes of clogs in water and sewer mains. Your sewage backup can be affected by overgrowing tree roots as they spread and find their way into the plumbing system. 

If you have experienced cracks, leaks or other broken pipes in the past, you are more likely to suffer from tree roots invading the pipes. As trees look for moisture, they are attracted to the water in waste and sanitary sewer pipes. If you live in wooded or forested areas, you should consider getting a video inspection conducted at your property frequently, as these can inspect the pipes for damage you didn't know was there from invading root structures.

Symptoms of a Clogged Drain

There are many symptoms your home plumbing will show you when there is a problem. Firstly, you will notice slow draining sinks or complete standing water.

If this problem continues with just one fixture (your bathroom sink, kitchen sink or toilet), it's potentially an issue with just that item. If you have any experience or a few basic tools, you could attempt to fix this yourself. We don't recommend that, though, and suggest you find a professional plumber to finish the job.

There are many home remedies that can fix small blockages and clogs, though. Combinations of lemon juice, baking soda and vinegar have been known to fix some kitchen and bathroom plumbing problems. Combining this with hot water can help you prevent pipe damage by using harsh chemicals.

Symptoms of a Clogged Drain

For areas of hard water, consider installing a water softener in your home. This won't rectify all your problems with minerals building up in your pipes, but it can help stop some.

All of this is not to say your home plumbing will not experience problems even with proper maintenance, but you can stop them from becoming worse issues that cost you more time and money. If you require assistance removing a blockage from your drains, please contact our team.

Are you looking for blocked drains specialists and septic tank cleaning in Warrington, Macclesfield, Northwich, and Cheshire?

No job is too large or too small- from a small domestic blockage to a commercial site emergency, next time you need emergency drain unblocking in the areas of Cheshire, give us a call on 0800 0725147.