Why Does My Sink Smell Bad?

If your kitchen or bathroom sink smells bad, you’re not alone. This is one of the most common plumbing complaints homeowners face. Odors can come from food buildup, bacteria, sewer gases, or drainage issues. The good news? Most causes are easy to identify and fix, and only a few require a professional plumber.

Common Causes of a Smelly Sink

1. Food and Grease Buildup in the Drain

Over time, small bits of food, grease, and oils settle in the drain and trap. When they start decomposing, they release a foul smell.

Fix:

• Run hot water for 1–2 minutes.

• Pour 1 cup of baking soda, followed by 1 cup of white vinegar.

• Wait 10 minutes and flush with hot water again.

2. Bacteria Growing in the P-Trap

The P-trap is the curved pipe under your sink. Its job is to hold water to block sewer gases. When the trap dries out or traps debris, bad smells rise up.

Fix:

• Turn on the faucet and let water run for 1 minute to refill the trap.

• If the smell persists, the trap may need to be cleaned or replaced.

3. Mold or Gunk on the Sink Stopper

Bathroom sink stoppers collect hair, toothpaste, soap scum, and bacteria — all of which cause a bad smell.

Fix:

• Remove the stopper.

• Clean it with hot water, dish soap, and an old toothbrush.

• Reinstall it once dry.

4. Garbage Disposal Odors

If you have a disposal, food residue often sticks to the blades and rubber splash guard.

Fix:

• Run ice cubes and coarse salt through the disposal to scrub the blades.

• Clean the rubber splash guard with a sponge and degreaser.

• Drop in a lemon slice for freshness.

5. Clogged or Dirty Drain Pipes

When the drain slows down, debris stays inside the pipe longer, creating a smell.

Fix:

Try clearing minor clogs with hot water and a plunger. If water drains slowly or backs up, you likely need a plumber.

6. Sewer Gas Leak

If your sink smells like rotten eggs or sewage, it could be due to:

• A dry P-trap

• A cracked drain pipe

• A loose connection

• A blocked vent pipe

Fix:

Sewer gas issues require a licensed plumber, these can affect health and indoor air quality.

7. Biofilm Buildup

Biofilm is a slimy layer of bacteria that forms inside pipes.

Fix:

Use a drain-safe enzymatic cleaner weekly to kill organic buildup.

How to Prevent Sink Odors

• Avoid pouring grease or oil down the drain.

• Run your disposal regularly.

• Clean stoppers monthly.

• Use hot water after washing dishes.

• Install a water filtration system if your home has hard water.

• Schedule an annual drain cleaning for best long-term results.

When to Call a Plumber

Call a professional if:

• The odor smells like sewage or rotten eggs

• The drain clogs repeatedly

• Water drains very slowly

• The smell returns after DIY fixes

• You notice standing water under the sink

These are signs of deeper plumbing issues like cracked pipes, vent problems, or sewer line concerns.

Call Vertical Plumbing at (480) 577-8720