Signs of a Sewer Gas Problem in Your Tucson Home

Every drain in your house has a built-in defense against sewer gas: a curved section of pipe called a P-trap, kept filled with water, that blocks gas from creeping back up. When that seal fails, or the vent line that carries gas up through your roof gets blocked, sewer gas doesn't stay where it belongs — it ends up in your home. That's not just unpleasant; it can be dangerous.

Here's how to tell a minor drain smell from a real problem, and why it's worth taking seriously.

What sewer gas actually is

As waste breaks down in your sewer line, it releases a mix of gases — hydrogen sulfide, ammonia, methane, and carbon dioxide are the main ones. Hydrogen sulfide is what gives it that rotten-egg smell. In small amounts, venting properly through your roof stack, none of this reaches you. The problem starts when it gets trapped indoors instead — through a dry trap, a blocked vent, or a break in the line.

A rotten-egg smell isn't always sewer gas

Before anything else: natural gas is scented with that same rotten-egg smell so a leak gets noticed. If you're not sure whether what you're smelling is a drain or a gas line — especially if it's sudden, strong, or you can't trace it to a bathroom or laundry area — treat it as a gas leak. Get everyone out, don't flip light switches or light anything, and call Southwest Gas or 911 from outside. Sort out the drains after.

Why it's more than a bad smell

Breathing concentrated sewer gas in a small or poorly ventilated space — a bathroom with the door shut, a laundry closet, a crawlspace — can cause headaches, dizziness, and nausea. If that's happening, get everyone outside into fresh air right away, and call 911 or seek medical care if symptoms don't clear. Don't stay inside to open windows or run a fan first — get out, then call. Methane adds a second risk: it's flammable, and a home with a venting problem can also have gas building up somewhere it shouldn't.

What causes it

Most often it's a dry or failed P-trap under a sink, tub, or floor drain, or a worn toilet wax ring — the seals meant to hold gas back. Less often, a main-line blockage or a blocked, damaged vent stack changes drainage pressure enough to siphon water out of an otherwise sound trap or push gas straight through its water seal; a cracked or disconnected vent can release sewer gas directly, with no trap involved at all.

On a septic system — common in Picture Rocks and outlying Marana — these same symptoms can point to the tank or leach field instead. Worth mentioning when you call.

Signs you have a sewer gas problem

A smell from one drain. This doesn't rule out sewer gas — it's often the likely cause. Every drain depends on its P-trap holding water, and in Tucson's dry air that water evaporates fast. Guest bathrooms, laundry sinks, and rarely-used floor drains are the classic case; running water for a minute usually clears it. (A kitchen sink is more often strainer or disposal residue.)

A smell from multiple drains. More than one drain smelling like sewage — especially with slow drainage or a backup — can point to a shared drain or vent problem. Not conclusive alone: several dry traps in seldom-used fixtures can smell at once too.

Slow or clogged drains in more than one place. One slow drain is usually local — grease, hair, a toy. Several at once usually means waste isn't clearing the main line, which can end in a backup if left alone.

Gurgling from toilets or drains. That's air moving through trap water as drainage or venting pressure shifts. It can point to a blockage or vent problem, and tends to worsen rather than resolve on its own.

More than one of these at once, or a trap that keeps drying out no matter how often you run it? Time to call rather than keep guessing.

What we actually check

What we check depends on what you're describing. Multiple slow or gurgling drains, or a backup, get diagnosed first — when a main-line problem looks likely, that means a camera scope through our sewer line or drain cleaning service. Residential sewer scopes run $129, all in — no separate service call stacked on top. A camera can't see through standing wastewater or a full blockage, so a backed-up line gets cleared first. If the line comes back clear, a blocked or capped roof vent is a separate check the camera doesn't confirm or rule out.

A smell from one drain gets a different check — the P-trap, a toilet's wax ring, or a blocked vent, not a camera scope. We'll explain the diagnostic charge up front, then check the source before quoting repairs.

Every repair we do carries a written 1-year materials-and-labor warranty on repairs. (see the full warranty terms)