What causes unpleasant odors from my drains?

What Causes Drain Odors and How to Fix Them

Unpleasant drain odors can make your home uncomfortable and may indicate plumbing issues. Common causes include:

• ✔ Dry P-trap: The curved pipe section under sinks and fixtures is designed to hold water, which blocks sewer gases. If a fixture isn't used regularly, this water can evaporate, allowing gases to escape.
• ✔ Biofilm buildup: Bacteria and organic matter can form a slime layer inside drains that produces odors.
• ✔ Food decomposition: Food particles trapped in garbage disposals or drain pipes can rot and cause smells.
• ✔ Sewer line issues: Damaged or blocked sewer lines can allow gases to back up into your home.
• ✔ Venting problems: Plumbing vent issues can cause negative pressure that pulls water from P-traps.
• ✔ Mold or mildew: Moisture around drains can promote mold growth that creates musty odors.

For infrequently used fixtures, simply running water for 30 seconds can refill the P-trap and eliminate odors. For persistent smells, a thorough drain cleaning may be necessary to remove biofilm and debris. If odors persist throughout your home, the issue might be with your sewer line or venting system, requiring professional inspection and repair.