Is sewer gas dangerous?

In the concentrations from a dry trap it's mostly unpleasant, but you shouldn't live with it — it doesn't belong inside your home, and a persistent smell means an open path to the sewer that needs fixing. And because natural gas odorant smells similar, any rotten-egg smell near a gas appliance means leave first and check later.

Why does the sewer smell come and go?

Intermittent smell usually tracks with use and airflow — a trap that dries out between uses, a vent problem that only siphons traps when a lot of water drains at once, or wind direction changing how the roof vent breathes. The pattern is a clue, so mention it when you call.

Why do I only smell it in one bathroom?

One-room smell almost always means one fixture: a dry trap in a shower or sink that rarely gets used, or a failed wax ring under the toilet. Run water down every drain in that bathroom first; if it comes back, the wax ring is the prime suspect.

Sewer Smell in the House? Causes & Fixes

What to do, step by step

1. Refill every dry P-trap

Every drain has a U-shaped trap that holds water as a seal against sewer gas. In a bathroom nobody uses, that water evaporates and the seal is gone. Run water down every rarely used drain — and pour a bucket of water into floor drains — then give it a day to see if the smell clears.

2. Check the toilets for a failed wax ring

The wax ring seals the toilet base to the drain. If a toilet rocks when you sit on it, or the smell is strongest right at the floor around the base, the ring may have lost its seal — sewer gas escapes even when everything looks dry. That's a straightforward fix, but it needs doing.

3. Look at the laundry area

The washing machine drain hose should sit properly in its standpipe, and that standpipe has a trap too. A hose pushed too far down, or a rarely used laundry sink with a dry trap, is a classic hidden source of the smell.

4. Consider a blocked vent stack

Your drains breathe through a vent pipe on the roof. When it's blocked — leaves, a bird's nest, debris — draining water pulls air through the traps instead, siphoning out the water seal. The telltale is gurgling drains along with the smell. Don't climb on the roof; note the gurgling and mention it when you call.

5. If the smell persists, suspect the sewer line itself

A cracked drain pipe under the slab or a failing sewer line can vent gas into the house with no visible leak. If you've refilled traps and the smell keeps coming back — especially with gurgling or slow drains — it's time for a camera inspection to see the line from the inside.

Warning signs to watch for

Gurgling from drains or toilets when water runs elsewhere in the house
Several drains running slow at the same time
The smell gets stronger when you run water or do laundry
A soggy, sunken, or unusually green patch in the yard over the sewer line
The smell keeps returning to the same room after you've refilled the traps

When to call a plumber

If running water down every drain didn't fix it within a day, or the smell comes with gurgling and slow drains, stop guessing — those are signs of a venting problem or a compromised sewer line, and neither improves on its own. A camera inspection finds the actual cause so you fix it once. One safety note: sewer gas smells like rotten eggs, but so does the odorant added to natural gas. If the smell is near a gas appliance or you're at all unsure, leave the house and call your gas company first.

A real licensed plumber answers 24/7 across Orange County — call (714) 587-5801 or text a photo of the problem and we'll tell you straight what it needs.

Call (714) 587-5801 Text a photo

Sewer Smell in Your House? Here's What It Means