How to repair a water leak under the sink?

A leak under the sink can have several causes. Here's how to diagnose and repair them:

Types of leaks:

1. Loose trap connection: Tighten the slip nut by hand or with an adjustable wrench. If the rubber gasket is worn, replace it ($2 to $5 at the hardware store)
2. Leaking supply hose (flexible): Rubber hoses last about 5 to 7 years. Replace with a braided stainless steel hose ($10 to $15) — more durable
3. Faucet leaking at the base: The O-ring or cartridge is worn. Cartridge replacement: $10 to $30 depending on brand
4. Poorly adjusted drain: The slip joint (trap adapter) has moved — tighten the nut. If the pipe is PVC/ABS, check it isn't cracked

Temporary repair (while waiting for the plumber):

• Self-fusing silicone tape: Stretches and fuses onto itself to seal a crack. Effective for 24-48 hours
• Pipe clamp: For a crack on a copper pipe, a clamp with a rubber sleeve can temporarily stop the leak

When to call a plumber:

• Leak in the wall (inside the wall or in the ceiling below)
• Punctured copper pipe (requires soldering or compression fitting)
• Persistent leak despite repairs