Blocked drains are unpleasant, and the problem can feel never-ending when it keeps coming back. If you are thinking, “Why are my drains blocked?”, it usually comes down to one simple issue: something has built up inside the pipes and slowed the flow of water until it can no longer pass. In many homes, the most common cause is fat, grease, and cooking oil being poured into a sink or drain.
It may look like it has gone away, but it cools inside the pipes, sticks to the sides, and starts to trap other debris. Over time, that build-up turns into a blockage and can lead to bigger drain blockages, damage, and even flooding in homes.
Why blocked drains happen so often
A blocked drain is rarely caused by one single thing. It is usually a mix of waste, soap, hair, food, and items that should have gone in the bin. Another common reason is that blockages start small, so you may not notice them at first. Then, one day, the water backs up quickly and you suddenly have an issue.
Common causes of blocked drains in the home
The common causes of blocked drains below will help you find the reason, remove the problem, and prevent it happening again.
1
Fat, grease, and cooking oil poured down sinks
Grease, fat, and cooking oil are a major cause of blocked drains. People often rinse a pan and let the oily water run into the sink, but the oil does not stay as a liquid for long. It cools, turns sticky, and starts causing blockages. It also traps food waste like pasta, rice, and other food scraps, which makes the blockage bigger.
A simple way to prevent this is to let the fat cool, pour it into a container, and dispose of it in the bin. This small change can save you time, money, and the stress of emergency repair work later.
2
Wet wipes and too much toilet paper
Many drain blockages start in the toilet. Even when a packet says “flushable”, wet wipes do not break down like toilet paper. Wet wipes, toilet paper, blocked drain problems often go together because wipes can stick to the inside of pipes and catch other things.
Be careful with thick toilet paper too. Using a lot at once can block the toilet, especially if the flow is already slow. If you have a large household, this can be a common problem that shows up more than once.
3
Sanitary products, nappies, and toiletries flushed down the toilet
Sanitary products, nappies, and some toiletries should never be flushed down the toilet. These items swell in water and can block pipes fast. Cotton buds are also a big cause, as they can catch on rough parts of the drain and build into a larger blockage.
A good rule to remember is simple: only flush what is meant to be flushed. Everything else should go in the bin.
Leaves and outdoor debris
Hair and soap
4
Hair and soap in the bathroom
In the bathroom, hair and soap are two of the biggest reasons for blocked drains. Hair can tangle and form a net inside the drain. Soap can leave a sticky layer that helps hair and debris stay in place. This often affects the shower, bath, and bathroom sinks.
Using a drain cover in the shower and bath helps catch hair before it goes down the drain. Cleaning the cover often is important, even if it feels like a small job.
5
Food waste and coffee grounds
Food waste is another common cause, especially in kitchen sinks. Small bits of food may seem harmless, but they can collect in bends in the pipes. Pasta and rice are a bigger risk because they swell and can quickly block a drain.
Coffee grounds are also a problem. They do not dissolve, and they can pack together and create a solid blockage over time. Scrape plates into the bin and use a sink strainer to catch food scraps before they go down.
6
Leaves and outdoor debris
Outside drains can become blocked by leaves and debris, especially after bad weather. If gutters overflow, the extra water can wash more debris into the drains and add to the build-up.
A drain cover or guard can help here too. If this keeps happening, it may be worth having the drains cleared and checked, so the problem does not return every week.
Ground coffee
Cotton buds
7
Tree roots and cracked pipes
Tree roots are a common cause of blocked drains when there are cracks in old pipes. Roots are drawn to wastewater, and they can grow into tiny gaps. As they grow, they reduce the flow and can break pipes further, which leads to bigger blockages and expensive repair work.
If you notice repeat blockages, bad smells, or slow drains across the whole property, a CCTV survey can help find cracks, roots, or a hidden break in the line.
Signs you may have a blocked drain
You can often spot a blockage before it becomes a full flood. You might notice water draining slowly from a sink, shower, or bath. Toilets may struggle to flush, or the water level may rise and fall.
You may also notice gurgling sounds, bad smells, or water coming back up after you run taps. If you notice these signs, it is best to deal with it early, while the blockage is still easy to clear.
What you can do at home to clear a simple blockage
For small blockages, you may be able to remove the problem yourself. Start by checking the plughole and trap under the sink for visible debris you can safely clear. A plunger can also help shift a blockage, especially in a sink or toilet.
Avoid pouring harsh chemicals down the drain, as they can damage pipes and may not fix the real cause. If the blockage will not clear, or it keeps coming back, it is safer to contact a drain unblocking team with the right experience and tools.
Who is responsible for blocked drains?
Responsibility depends on where the blockage is. If it is within your property boundary, it is usually the homeowner’s responsibility. If it is in shared sewers or a public line, it may be the local water company.
If you are not sure, a professional can help you find where the blockage is and advise what to do next.
When to get help fast
If wastewater is backing up, if you have flooding, or if more than one drain is blocked at the same time, do not wait. These problems can cause serious damage to your home.
Getting the drains cleared quickly can reduce risk and may prevent a bigger repair. If you need help, get in touch. Contact a drainage specialist if you need urgent advice or support, including help that is available 24/7.
Common Causes Of Blocked Drains: Final Thoughts
Most causes of blocked drains come from daily habits. The best prevention is to keep the wrong things out of the drains. Put wipes, cotton buds, sanitary products, nappies, and food waste in the bin. Do not pour cooking oil or grease into sinks.
Use a cover in the shower to catch hair, and clear it often. Small actions each day can prevent a common problem from turning into a costly one.
Struggling with a drain blockage in your bathroom or kitchen? Let us help. Tru Flow Drainage is a drainage contractor that has been resolving drainage issues for local homes, businesses, and property developers for more than 25 years.
