Why Does My Drain Keep Blocking?

Having a drain cleared only for it to block again within weeks is incredibly frustrating. If this keeps happening to you, there's almost certainly an underlying reason — and once you identify it, the problem becomes much easier to solve permanently.

The Most Common Reasons for Recurring Drain Blockages

1. Fat and Grease Build-Up (Kitchen Drains)

This is the number one cause of recurring kitchen drain blockages in Derby homes. When cooking fat, oil, and grease are poured down the drain — even mixed with hot water and washing up liquid — they cool and solidify further down the pipe. Over time, this creates a sticky residue that builds up layer by layer until the pipe is blocked.

A drain jetting service will clear this effectively. But if fat continues to go down the drain, the blockage will return. The only long-term solution is to change the behaviour.

2. Hair and Soap Scum (Bathroom Drains)

Hair shed during bathing and showering combines with soap, conditioner, and skin care products to create a tangled, sticky mass that gradually blocks the drain. Bathroom drain blockages tend to build slowly and are often first noticed as slow drainage before becoming a complete blockage.

A simple drain cover or hair catcher on the shower drain can dramatically reduce bathroom drain blockages. They cost a few pounds and can be cleaned in seconds.

3. Root Intrusion

Tree roots are drawn to the moisture and nutrients inside drain pipes. They can penetrate through even hairline cracks in older clay pipes and, once inside, grow rapidly into a mass of roots that fills the pipe. Roots can be cut and cleared, but they will regrow unless the pipe is relined or replaced to seal the entry point.

Root intrusion is particularly common in Derby's older residential streets where mature lime, oak, and sycamore trees line the roads. If you have a tree within 10 metres of your drain run and are experiencing recurring blockages, root intrusion should be investigated via CCTV survey.

4. Cracked or Broken Pipes

A cracked drain pipe allows soil and debris to enter the drain from outside, gradually accumulating and causing blockages. The crack itself can also create a step or narrowing that catches debris. Clearing the blockage without addressing the cracked pipe means the problem will keep recurring.

5. Incorrect Pipe Gradient

Drain pipes need to be laid at the correct gradient (typically 1:40 to 1:80) to allow waste water to flow freely under gravity. Pipes laid too flat cause slow flow and sediment build-up. Pipes laid too steeply can cause the water to outpace the solids, leaving solids behind to accumulate. Incorrect gradients are common in older properties or where amateur DIY drain work has been carried out.

6. Bellied Pipes

A "belly" in a drain pipe is a sagging section where the pipe has dropped due to ground movement or poor installation. This creates a low spot where water sits and solids accumulate, eventually causing a blockage. Bellied pipes can only be identified via CCTV survey and require either relining or replacement to correct.

7. Foreign Objects

Children's toys, wet wipes labelled as flushable, cotton wool, and many other items regularly cause drain blockages in Derby homes. These items don't dissolve in water and can create an anchor point around which other debris accumulates. If foreign objects are entering your drain regularly, a stopcock or grating over the drain opening can help.

When to Get a CCTV Survey

If your drain has blocked more than twice in the past 12 months, we recommend a CCTV drain survey. This will confirm whether there is a structural problem causing the recurring blockages, and will inform the most cost-effective repair strategy.

Preventing Future Drain Blockages

• Never pour fat, oil, or grease down the kitchen drain
• Use a hair catcher on shower and bath drains
• Only flush toilet paper — never wipes, cotton wool, or sanitary products
• Lift and clean external drain covers periodically, especially in autumn
• Consider an annual high-pressure drain maintenance service
• If you have mature trees near your drain runs, get a CCTV check every 2-3 years