How to Prevent Blocked Drains: 10 Simple Tips

The average UK household spends around £140 each time a blocked drain needs professional clearing. According to water industry data, there are over 300,000 sewer blockages in England every year, and the majority are caused by things that should never have gone down the drain in the first place. The good news: most blockages are preventable with a few simple habits that cost little or nothing to adopt.

1. Fit Drain Guards on Every Plughole

A stainless steel or silicone drain guard (sometimes called a drain strainer) sits over the plughole and catches hair, food scraps, and debris before they enter the pipe. They cost £2–£5 from any supermarket or hardware shop and are the single most effective preventive measure you can take.

Fit one in the kitchen sink, bathroom basin, shower tray, and bath. Clean them out every few days — it takes ten seconds and saves you a call-out fee later.

2. Never Pour Fat, Oil, or Grease Down the Sink

This is the number one cause of kitchen drain blockages in the UK. Fat goes down the drain as a liquid but solidifies as it cools, coating the inside of the pipe and gradually narrowing it until nothing can pass. Thames Water removes around 30,000 fat blockages from London's sewers every year alone.

Instead: let cooking fat cool and solidify in the pan, then scrape it into the bin. For oils, pour them into an old jar or container and bin it. Wiping greasy pans with kitchen roll before washing them also helps significantly.

3. Don't Flush Wet Wipes, Cotton Buds, or Sanitary Products

The only things that should go down a toilet are human waste and toilet paper. Everything else — including wet wipes marketed as “flushable” — should go in the bin. Water UK testing has shown that even branded flushable wipes take far longer to break down than manufacturers claim, and they frequently snag on pipe joints and build up into blockages.

Cotton buds, dental floss, nappies, and sanitary products cause similar problems. Keep a small bin with a lid next to every toilet in your house.

4. Run Hot Water After Every Wash-Up

After washing dishes, run the hot tap for 30 seconds. This helps flush any residual grease through the pipe before it has a chance to cool and solidify on the pipe walls. It's a small habit that makes a genuine difference over months.

5. Monthly Hot Water Flush

Once a month, pour a full kettle of boiling water down each sink and basin in the house. This dissolves accumulated soap scum and soft grease before it hardens into a proper blockage. For an extra boost, add a tablespoon of washing soda (soda crystals, available for about £1 from most supermarkets) before the boiling water.

This is maintenance, not a cure. If a drain is already slow, a hot water flush won't clear an existing blockage — see our DIY vs professional guide for what to do in that case.

6. Scrape Plates Before Washing

Get into the habit of scraping food scraps off plates into the bin (or compost) before they go in the washing-up bowl or dishwasher. Rice, pasta, tea leaves, and coffee grounds are particularly problematic — they swell with water and clump together in pipes.

If you have a food waste caddy (many councils in England now provide kerbside food waste collection), use it. Everything from vegetable peelings to plate scrapings can go in there instead of down the sink.

7. Clean the U-Bend Every 6 Months

The U-bend (trap) under your kitchen sink is designed to hold water that blocks sewer gases, but it also collects grease and debris over time. Twice a year, put a bucket underneath, unscrew the U-bend, and clean it out. It's a five-minute job that prevents the most accessible section of your drainage from narrowing.

You don't need any tools beyond a pair of rubber gloves and possibly a wrench for stiff fittings. Bathroom basins have the same type of trap and benefit from the same treatment.

8. Keep External Drains Clear of Debris

External gully drains (the ones with a grid cover near your house, often by the kitchen or at the bottom of a downpipe) are entry points for leaves, moss, and garden debris. Check these quarterly and remove anything sitting on or just below the grate.

If a gully is slow to drain even when the grate is clear, the trap below may need cleaning out. You can usually reach in with rubber gloves and scoop out accumulated silt.

9. Be Careful With Garden Planting Near Drains

Tree roots are one of the most common causes of serious drain blockages, particularly in older properties with clay pipes. Roots seek out moisture and can penetrate pipe joints, growing inside the drain and creating a mass that traps debris.

If you're planting trees or large shrubs, keep them at least 3 metres from any known drain runs. Species with particularly aggressive root systems — willow, poplar, oak, and ash — should be planted even further away. If you already have mature trees near drain lines, consider a preventive CCTV survey every 2–3 years to catch root ingress early.

10. Know Where Your Drains Run

Most homeowners have no idea where their underground drains go. Knowing the layout of your drainage — where the manholes are, which direction the pipes run, and where your drains connect to the public sewer — helps you spot problems early and describe them accurately if you need to call for help.

You can buy drainage plans for your property from your local water company for around £20–£30. Alternatively, a CCTV drain survey will map the full system and identify any existing issues. It's a particularly good investment if you're buying a property — drainage problems aren't covered by a standard building survey.

Seasonal Drain Maintenance

Autumn: Falling Leaves

September through November is peak season for leaf-related drain blockages. Fallen leaves collect on gully grates, in gutters, and around manhole covers, forming a wet mat that blocks water flow. Clear your external drain covers weekly during autumn, and make sure gutters and downpipes are free of leaf debris. Gutter guards (around £5–£10 per metre) are a worthwhile investment if you have overhanging trees.

Winter: Freezing Temperatures

Exposed waste pipes (common under mobile homes, in unheated garages, and on external walls) can freeze in sustained cold weather, blocking the pipe completely. Lagging exposed waste pipes with foam pipe insulation (around £3–£5 for a 2-metre length from any DIY shop) prevents this.

If a waste pipe does freeze, never pour boiling water directly onto it — the thermal shock can crack plastic pipes. Instead, wrap the frozen section in towels soaked in warm water and let it thaw gradually.

Spring: Post-Winter Check

After winter, do a walk-around of your property and check all external drain covers, gullies, and manholes. Ground movement from freeze-thaw cycles can displace manhole covers and crack pipe joints. If you notice any new damp patches, subsidence, or slow draining that wasn't there before winter, it's worth getting a professional to take a look.

When to Get a Preventive CCTV Survey

A CCTV drain survey costs £100–£200 and gives you a clear picture of the condition of your underground drainage. Consider booking one if:

• You're buying a property (particularly one built before 1970 with original clay pipes)
• You've had two or more blockages in the past 12 months
• You have mature trees within 5 metres of a drain run
• You're planning a home extension or conservatory that might affect drainage
• You notice persistent damp near ground level that you can't explain

Think of it as a health check for your drains. Catching a cracked pipe or early root ingress before it causes a blockage is far cheaper than dealing with the emergency when it happens.