Is sewer smell in the house dangerous?

At the low concentrations typical in homes, sewer gas is unpleasant rather than acutely dangerous, but it shouldn't be ignored: prolonged exposure can cause headaches and nausea, and a persistent smell means sewer gas has a path into your home — often a dry trap, failed seal or cracked pipe that will worsen. Strong smells with symptoms warrant ventilating and getting it fixed promptly.

Why does my bathroom smell like sewer when the shower runs?

Running water can pull air through the pipes; if a trap is marginal, a vent is blocked or there's biofilm in the shower drain, that airflow carries sewer smell into the room. Wastewater from the shower can also disturb a partial blockage downstream, releasing trapped gas. Clean the drain and check traps first; a smell that only appears with water use often points at venting or a developing blockage.

How do I get rid of a sewer smell in the house?

Work from cheapest to dearest: pour water (with a dash of oil) into all floor drains and unused fixtures to refill traps; scrub biofilm from smelly shower drains; check the outdoor overflow relief gully is clear and its grate loose; then if the smell persists, book a plumber to smoke-test or camera the line — persistent smells often trace to a partial blockage or cracked pipe.

Sewer Smell in Your House? Causes, Fixes & When to Worry

Q: Why does my drain smell like rotten eggs?

A rotten-egg smell is hydrogen sulphide — sewer gas. The most common cause is a dried-out water trap in a floor drain or unused fixture, which normally blocks gas from the sewer. Other causes are biofilm build-up in the drain, a blocked overflow relief gully, a partial sewer blockage, or a cracked pipe or vent. Pour a bucket of water into unused drains first; if the smell persists, the source needs proper diagnosis.

Chrome floor drain in a white-tiled Australian bathroom

Why does my drain smell like rotten eggs?

Rotten eggs = hydrogen sulphide = sewer gas escaping where it shouldn't. The usual suspect is a dried-out water trap — the water sitting in the U-bend of every drain is what seals sewer gas out, and in unused drains it simply evaporates.

Every fixture in your home — sinks, showers, floor wastes — has a trap holding a plug of water between your room and the sewer. Guest bathroom nobody uses? Laundry floor waste behind the machine? A few weeks of evaporation and the seal is gone; the sewer is now ventilating into your house.

The five causes, cheapest fix first

Dry trap (free). Pour a bucket of water into every floor waste and unused fixture. A tablespoon of cooking oil on top slows future evaporation. If the smell fades over a day — solved.
Biofilm in the drain (nearly free). Hair, soap scum and bacteria coat the first metre of shower and basin drains and can smell convincingly like sewage. Remove the grate, scrub with a bottle brush and hot soapy water. (Smells worst when water runs — the flow pushes air past the gunk.)
Blocked overflow relief gully ($0 to check). The ORG is the grated outdoor drain that's designed to overflow outside instead of inside if the sewer blocks. If it's buried under pot plants, paved over, or its grate is stuck fast, sewer gas and worse can back up toward the house. Make sure it's clear, and the grate sits loose.
Partial sewer blockage (plumber). Gurgling + smell + slow drains = a blockage building downstream. Gas trapped behind the obstruction escapes through your fixtures. This one gets worse, never better — see blocked drains.
Cracked pipe or failed vent (plumber). A persistent smell you can't trace — especially in one room, or strongest at skirting level — can be a cracked sewer pipe under the slab or a blocked/disconnected vent stack. This is the one you don't ignore: wastewater may be leaking where you can't see it.

Is sewer smell dangerous?

At typical household concentrations it's unpleasant rather than acutely dangerous — but it's never normal. A persistent smell means sewer gas has a path into your home, and prolonged exposure can cause headaches, nausea and eye irritation. Strong smell + symptoms: ventilate and get it fixed promptly.

The real risk isn't usually the gas — it's what the gas is telling you. A failed seal gets worse. A partial blockage becomes an overflow. A cracked pipe under the slab becomes a soggy foundation. Cheap fix now beats expensive fix later, every time.

Finding the source: a 10-minute hunt

One room or everywhere? One room points at that room's trap, seal or drain. Everywhere points at the ORG, vent or main line.
Constant or only when water runs? Constant = dry trap or crack. Only-with-water = biofilm, venting, or a partial blockage being disturbed.
Sniff low. Sewer gas sources smell strongest at floor level — check floor wastes and the base of the toilet (a failed wax/rubber pan seal is a classic).
Check outside. Smell near the ORG or a soggy, suspiciously green patch of lawn moves this from "smell" to "sewer problem".
After the flush test: toilets gurgling when other fixtures drain is the classic early sign of a main-line blockage.

Done the free fixes and it still smells? Stop guessing. We locate odour sources with smoke testing and CCTV inspection — you get footage, a written diagnosis and a fixed quote. Usually within the hour, because nobody should live in a house that smells like a sewer. Even we don't, and we love sewers.

That smell? Your house is trying to tell you something.

Why does my drain smell like rotten eggs?

The five causes, cheapest fix first

Is sewer smell dangerous?

Finding the source: a 10-minute hunt

Smell won't quit? We'll find it.