The Top 5 Causes of Blocked Drains in the UK

A blocked drain is one of the most stressful household emergencies. From foul odours to overflowing toilets, the disruption is immediate. But what actually causes these blockages? Through thousands of CCTV Drainage Surveys across London, and London, the CleverWorks team has identified the top 5 culprits.

1. "Flushable" Wet Wipes

Despite what the packaging might claim, the vast majority of wet wipes are not truly flushable. Unlike toilet paper, which breaks down rapidly in water, wet wipes are bound together with plastics and synthetic fibres. When flushed, they snag on minor imperfections in the pipework, accumulate, and eventually form massive, impenetrable blockages. Rule of thumb: Only flush the 3 Ps (Pee, Poo, and Paper).

2. FOG (Fats, Oils, and Grease)

Pouring cooking oil or bacon fat down the kitchen sink might seem harmless when it's hot and liquid. However, as soon as that fat hits the cold underground drainage pipes, it solidifies. Over time, this creates a thick, sticky coating on the inside of the pipe—often referred to as a "fatberg." This sticky layer then catches food scraps and debris, rapidly closing off the pipe entirely.

3. Tree Root Ingress

This is a very common issue in older properties, particularly those with Victorian clay pipes. Tree roots naturally seek out moisture and nutrients. Even a microscopic hairline crack in a pipe joint is enough for a tiny root hair to enter. Once inside, the root thrives, growing into a dense mass that completely chokes the pipe and often causes the pipe to shatter under the pressure. The only way to diagnose this accurately is with a professional CCTV drainage survey.

4. Hair and Soap Scum

In the bathroom, the combination of long hair and soap scum is lethal to your plumbing. Hair binds together, and the sticky soap scum acts like cement, creating tough clogs in shower traps and bath drains. Using a simple, inexpensive hair catcher over your plughole can prevent 90% of these blockages.

5. Structural Damage and Collapsed Pipes

Sometimes, a blockage isn't caused by what you put down the drain, but by the drain itself. Ground movement, subsidence, heavy vehicle traffic above, or simply old age can cause pipes to crack, misalign (displaced joints), or collapse entirely. When a pipe collapses, earth and stones fall into the channel, stopping the flow of water instantly.

How to Fix a Stubborn Blockage

While minor sink clogs can sometimes be cleared with baking soda and vinegar or a plunger, recurring or severe blockages require professional intervention. If you find yourself constantly plunging the same toilet, it's time to call in the experts. We use high-pressure water jetting to obliterate fatbergs and root masses, and we can perform a CCTV survey to ensure your pipes are structurally sound.