A sink that blocks repeatedly almost always has one of a few causes. Kitchen sinks and bathroom basins block for different reasons, so it helps to deal with them separately.
Kitchen sinks
Fat, oil and grease
This is the number one cause. Fat goes down the sink warm and liquid, then cools and sets on the inside of the waste pipe. Each time, the gap gets narrower. Washing-up liquid does not stop this; it only moves the grease a bit further along before it sets.
Food waste
Rice, pasta, coffee grounds, tea leaves and vegetable peelings all stick to grease and swell in water. A sink strainer catches most of it.
The gully outside
Many kitchen sinks drain into an open gully outside. Grease builds up there too, and once the gully is coated, the sink backs up even if the pipe under the sink is clear.
The washing machine or dishwasher
Appliances often share the sink waste. If the pipe is partly blocked, the sudden rush of water from a machine can push water back up into the sink.
Bathroom basins
Hair and soap
Hair combines with soap and toothpaste to form a sticky mat just below the plug and in the trap. It builds up slowly, which is why basins tend to get gradually slower rather than blocking suddenly.
Limescale
In hard water areas, scale can narrow pipes and give hair and soap something to cling to.
When the pipe itself is the problem
Sometimes the cause is how the waste pipe was installed. Long runs with very little fall, lots of bends, or a pipe that has sagged between clips all let debris settle. If you clean the trap and change your habits but the sink still blocks every few weeks, the pipework may need looking at.
What helps
- Wipe greasy pans with kitchen roll before washing, and put cooled fat in the bin.
- Use a sink strainer in the kitchen and a hair catcher in the bathroom.
- Clean the trap every few months.
- Run hot tap water after washing up to help carry residue away.
- Get the gully and drain cleaned if grease has built up beyond the sink. Drain cleaning deals with build-up before it becomes a full blockage, and drain jetting clears heavy grease from the pipe.
Signs it is more than a sink problem
If several fittings are slow, or water rises in the sink when the toilet is flushed or the bath empties, the blockage is likely to be in the underground drain rather than the sink. See blocked drains.
If you are in Southampton, find out more about blocked sinks in Southampton or get in touch.