If water sits in your sink and drains slowly or not at all, the cause is usually a blockage in the trap or drain line rather than a major plumbing failure.
Most sink drainage problems are caused by buildup, not broken pipes.
The Most Common Reasons This Happens
1. Blocked U-Bend (Trap)
The curved pipe under your sink is designed to trap debris and prevent sewer gas from rising.
Over time, grease, food, soap, and hair can build up inside it.
This is the most common cause of a sink not draining.
2. Grease or Food Buildup
Kitchen sinks often clog due to grease solidifying inside pipes.
This gradually restricts water flow.
3. Hair and Soap Residue
Bathroom sinks often clog from hair and soap forming dense blockages.
If your shower also drains slowly, see:
→ Why Is My Shower Not Draining?
4. Vent or Pressure Issue
If the sink drains slowly and you hear gurgling, air may be trapped in the system.
Related issue:
If multiple fixtures are affected:
5. Deeper Drain Line Blockage
If water backs up into other fixtures, the blockage may be further down the system.
If your toilet bubbles or gurgles, see:
Is This Serious?
It may be minor if:
- Only one sink is affected
- Drainage improves after plunging
- The issue developed gradually
It may require attention if:
- Water backs up
- Multiple drains are slow
- There is a strong smell
What You Can Do
If your sink is not draining, you can:
- Remove and clean the U-bend
- Use a drain snake
- Flush with hot water (for grease)
- Monitor other fixtures
If the problem affects multiple drains, further inspection may be required.
For related issues, see:
→ Sink & Drain Problems Explained
→ Why Is My Sink Gurgling?
→ Why Is My Shower Not Draining?
→ Why Is My Toilet Bubbling?
→ Plumbing Problems Explained