How to Care for Drains and Clear a Slow Sink

Keep sinks, baths and outdoor drains flowing with simple habits, safe DIY unblocking steps, what to avoid pouring away and when to call a drainage firm.

Most blocked drains start as slow drains, and most slow drains are caused by habits that are easy to change. Fat, hair, wipes and soap scum build layer by layer until water has nowhere to go. A few minutes of prevention each month, and knowing what to try before calling for help, will spare you smelly kitchens and flooded bathrooms.

Know your drains

• Internal wastes: Pipes from sinks, baths, showers and appliances. They usually have a trap, a U-bend that holds water and stops smells.
• Soil pipe: Carries toilet waste, typically a larger pipe.
• Outdoor drains: Gullies at ground level take water from downpipes, sinks and patios, and manholes give access to the main drain.
• Responsibility: Drains within your boundary generally belong to you. Shared drains, and sewers beyond your boundary, are normally the water company's. Check with your water company if unsure.

What causes blockages

Daily habits that work

1. Wipe greasy pans with kitchen paper before washing.
2. Use sink strainers in the kitchen and a hair catcher in showers.
3. Bin wipes, nappies and cotton buds rather than flushing.
4. Flush hot water down the kitchen sink after washing up.
5. Pour used cooking oil into a container and bin it.

DIY unblocking, in order of effort

1. Hot water. For a mild kitchen sink slowdown, pour a kettle of very hot, but not boiling, water in stages. Avoid boiling water on plastic pipes or cracked porcelain.
2. Plunger. Block the overflow with a wet cloth, then plunge firmly.
3. Bicarbonate of soda and vinegar. Gentle and low risk, though it works best on light build-up.
4. Clean the trap. Put a bucket underneath, unscrew the trap and clear it by hand. Wear gloves.
5. Drain rod or hair snake. Reach further into a basin or bath waste.
6. Chemical drain cleaners. Use sparingly and carefully, following the instructions. They are harsh on pipes and skin, and dangerous if mixed or if a plumber later has to work in the standing water.

If water backs up elsewhere, for example the bath gurgles when you flush, the problem is deeper and a snake will not fix it.

Outdoor drains and gullies

• Lift the grate and scoop out leaves and silt every few months, especially in autumn.
• Rinse with a hose.
• Keep patio and path areas clear of moss and mud that wash into gullies.
• Do not pour fat or paint into outdoor drains; it ends up in the same system.

Our gutter cleaning guide covers the roof end of the system.

Signs you need a professional

• More than one fixture is slow or blocked
• Foul smells that return after cleaning
• Water bubbling or gurgling
• Wet patches in the garden above drain runs
• Manholes that are full or overflowing
• Rats seen near drains

Drainage firms use rods, jetting and CCTV surveys. Typically a simple unblocking might cost from around £70 to £200, with more complex work costing more, and prices vary by region and time of day. Ask for the quote in writing, and what is included before they start.

Prevention for rented homes

Tenants are usually expected to avoid causing blockages through misuse, while landlords handle faults in the system itself. Report persistent problems in writing. See tenant vs landlord responsibilities.

If the problem is beyond DIY, you can search for plumbers and drainage specialists on Compito, compare ID-verified providers by postcode and send a request.

A worked example: a slow kitchen sink

A kitchen sink drains slowly and smells. The householder removes the strainer debris, runs hot water, then places a bucket under the trap and unscrews it. It is full of grey, greasy sludge. Cleaned and refitted, the sink runs freely. They add a strainer and start wiping pans with paper. Total cost: a few pounds for a bucket and gloves, plus twenty minutes. If the sink had stayed slow after the trap was clear, the next step would have been a drain rod or a professional.

How to clean a trap safely

1. Clear under the sink and put a bowl or bucket beneath the trap.
2. Unscrew the collar nuts by hand where possible, supporting the pipe.
3. Tip out and clean the trap, then check the pipe into the wall for debris.
4. Refit with the washers seated properly and tighten by hand, plus a small nip with a tool if needed.
5. Run the tap and watch for drips before you leave it.

Wear gloves and protect eyes, since waste can splash.

Washing machine and dishwasher drains

If a washing machine drain hose smells or drains slowly, check the filter and pipe behind it as the manual describes. Do not run it to flush a blocked waste. Dishwashers also have filters that need regular cleaning; blocked filters are a frequent source of smells.

Things not to do

• Do not use a pressure washer or drain rods near old, fragile pipes without advice.
• Do not mix chemical cleaners.
• Do not lift manhole covers unless you know what you are doing; they can be heavy and dangerous.
• Do not ignore sewage smells inside the home. They can point to a dry trap, failed seal or a vent problem.

Prevention calendar

• Monthly: clean sink strainers and run hot water down the kitchen sink.
• Quarterly: clean shower and bath wastes and clear outdoor gullies.
• Autumn: clear leaves from gullies and check around downpipes.
• Annually: pour water down rarely used basins and floor drains to keep traps full.

Frequently asked questions

Is it okay to pour bleach down a drain?

Occasional diluted use is common, but it does not clear fat blockages and should never be mixed with other cleaners. Use it carefully.

Why does my kitchen sink smell?

Often it is fat and food residue in the waste pipe or trap. Cleaning the trap and flushing with hot water usually helps. If it persists, check for a dry trap or vent issue.

Who is responsible for a blocked shared drain?

It depends on the layout, but shared drains are often the water company's responsibility. Contact them to check before paying for a private repair.

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