Don't Ignore a Slow Drain

A sink that drains slowly might seem like a minor inconvenience, but it is almost always a sign that something is accumulating inside your pipes. Left untreated, a slow drain becomes a fully blocked drain — and the more advanced the problem, the harder (and more expensive) it is to fix. Early diagnosis is key.

The Most Common Causes

1. Hair and Soap Scum (Bathroom Sinks & Showers)

Hair is the number one culprit in bathroom drains. It tangles together with soap scum to form a sticky, fibrous mass that clings to the inside of pipes. Even with a drain cover in place, fine hairs accumulate gradually. The build-up typically forms just below the drain opening, making it relatively easy to remove once identified.

2. Grease and Food Particles (Kitchen Sinks)

Cooking fat, oil, and grease may be liquid when poured down the drain, but they solidify at room temperature and stick to pipe walls. Over time, layers build up and narrow the pipe's internal diameter. Food particles trap themselves in this sticky lining, accelerating the blockage.

3. Toothpaste, Soap, and Mineral Deposits

Hard water areas are particularly prone to mineral scale build-up inside pipes. Combined with toothpaste residue and bar soap, this creates a hard, chalky coating that progressively reduces pipe diameter. This type of build-up is often found further down the drain than hair clogs.

4. Foreign Objects

Small items — bottle caps, cotton buds, children's toys, jewellery — can partially lodge in a drain and act as a trap for subsequent debris. Water may still pass around the object initially, but the blockage grows over time.

5. Pipe Scale or Corrosion

In older homes, the internal walls of metal pipes can corrode or develop significant scale deposits. Unlike organic blockages, this cannot be cleared with a plunger or chemicals — it may require pipe replacement.

6. Partial Sewer Line Blockage

If multiple sinks or drains in your home are draining slowly at the same time, the problem is likely in the main sewer line rather than individual fixtures. Tree root intrusion, collapsed pipes, or a build-up deep in the system are possible causes.

How to Diagnose the Cause

  1. Observe which drains are affected. One drain = likely a local blockage. Multiple drains = likely a main line issue.
  2. Check the location. Bathroom slow drain → suspect hair/soap. Kitchen slow drain → suspect grease.
  3. Look into the drain opening. Use a torch to check for visible debris just below the cover.
  4. Remove and inspect the drain cover or pop-up stopper. Hair and soap scum often wrap around the stopper mechanism.
  5. Listen for gurgling sounds. Gurgling from another drain when you flush the toilet suggests a main line issue.
  6. Check for odours. A persistent sulphur or sewage smell points to a deeper blockage or a dry P-trap.

What to Do Next

Once you have identified the likely cause, you can match it to the appropriate solution:

  • Hair/soap: Remove by hand or with a drain cleaning tool, then flush with hot water.
  • Grease: Hot water flush, followed by a baking soda and vinegar treatment or an enzyme-based drain cleaner.
  • Mineral scale: A descaling product or professional hydro-jetting.
  • Multiple drains affected: Contact a professional plumber for a main line inspection.

Act Early

A slow drain that is caught and treated early takes minutes to fix. The same problem left for weeks or months may require a drain snake, a professional callout, or even pipe repair. Regular maintenance — covered in our preventive maintenance guides — is always the better long-term strategy.