What Causes a Sewage Smell in Your House?

A whiff of sewage inside your home is hard to ignore, and for good reason. That rotten-egg or musty smell is your house telling you something is off with the plumbing. Sometimes the fix is simple. Other times the odor is the first sign of a leak or backup that needs professional attention.

Here is what commonly causes that smell and how to figure out where it is coming from.

Common Sources of a Sewage Smell

Several plumbing issues can let sewer gas escape into your living space:

• A dry P-trap. Every drain has a curved pipe that holds a small pool of water to block sewer gas. If a sink, floor drain, or tub goes unused for a while, that water evaporates and the barrier disappears, letting odor drift up.
• A damaged or blocked vent. Plumbing vents carry sewer gases up and out through the roof. If a vent is cracked, clogged with debris, or blocked by a bird nest, those gases can back into the home instead.
• A blocked drain. Buildup in a drain traps waste and creates odor, and a partial clog can push smells back into the room.
• A sewer leak. A cracked or broken sewer line under or around the home can release gas and contaminated water into crawl spaces, walls, or the yard.
• Biofilm buildup. A slimy layer of bacteria can coat drain walls and garbage disposals, giving off a foul smell even when the drain flows fine.

How to Locate the Source

A little detective work can narrow things down before you call for help:

• Note which room the smell is strongest in and whether it comes from a specific drain.
• Run water in rarely used fixtures. If the smell fades, a dry trap was likely the cause.
• Check for gurgling or slow drains, which point to a venting or clog problem.
• Pour a little water into floor drains in the garage, laundry room, or lower level.
• Notice when the smell appears. A constant odor is different from one that only shows up after you flush or run water.

When the Smell Signals Something Serious

A dry trap or a dirty disposal is a minor fix. But a persistent sewage smell that will not go away, especially one paired with other symptoms, can mean a real leak or backup. Watch for these red flags:

• The odor returns no matter what you clean or refill
• Multiple drains are slow or gurgling at once
• You see damp spots, staining, or pooling near the lowest level
• The smell is strong outdoors near the sewer line or yard
• Toilets or tubs back up along with the odor

These signs suggest wastewater may be escaping where it should not, and that water is a biohazard. Do not dig into a suspected sewer line or expose yourself to standing wastewater. Keep the area ventilated and off-limits until it is assessed.

If a simple refill or cleaning does not clear the air, it is time to bring in a professional. Tri Tech serves Burbank and Greater Los Angeles 24/7. Call our 24-hour line and we will locate the source, address any leak or backup, and get your home smelling clean and safe again.