Why Do My Drains Keep Blocking? Common Causes and Prevention

Repeated blockages are not bad luck. There is usually a clear cause, either in how the drains are used or in the system itself. Knowing the cause saves you from the same problem again.

The most common causes

• Grease and oil in the kitchen sink: it solidifies inside the pipe and traps food waste.
• Hair and soap in bathrooms: they bind together and narrow the pipe over time.
• Wipes and non-degradable items flushed down the toilet.
• Insufficient pipe gradient, which lets debris settle.
• A main line blockage that shows up in more than one bathroom.

Simple blockage or main line?

If only one sink is affected, the blockage is usually close to it. If water comes up the floor drain when the washing machine runs, or several bathrooms are affected at once, the blockage is more likely in a shared or main line and needs a wider inspection.

Practical prevention

• Never pour oil or grease down the sink; collect it and put it in the bin.
• Use strainers on basins and shower drains.
• Do not flush wet wipes or cotton.
• Run hot (not boiling) water down the kitchen sink from time to time.
• Run water in unused bathrooms occasionally so traps do not dry out and cause odours.

When to call a technician

If a plunger does not work, if blockages return quickly, or if more than one bathroom is affected. Avoid mixing chemical drain cleaners — they can release dangerous gases.

Related pages: Drain cleaning · Bathroom & kitchen fixtures · Pipe repair & installation