Sewer Smell in House

A sewer smell in the house usually comes from one of three places: a drain trap that has dried out, a vent that is not letting sewer gas escape, or a crack or leak somewhere in the drain line. The first is common, harmless once fixed and easy to sort out yourself. The other two need a licensed plumber, and a smell that comes with backups or gurgling needs one soon. Before anything else, make sure it is not gas.

The short answer

Every drain in your house has a trap, a bend of pipe that holds a little water. That water seals the drain, so sewer gas cannot rise through it into the room. When a shower, sink or floor drain goes unused for weeks, the water evaporates and the seal is gone.

If the smell is near one fixture you rarely use, a dry trap is the likely cause. If it moves around the house, comes and goes with the wind or with flushing, or appears with slow or gurgling drains, the cause is more likely a vent or the line itself.

First, rule out gas

Natural gas has an added odour that many people describe as rotten eggs, which can be hard to tell apart from sewer gas. If your home has gas appliances and you are not sure what you are smelling, treat it as gas. Do not switch lights or appliances on or off. Leave the house, and call the gas utility or 911 from outside.

What to check first

These checks are safe and need no tools.

1. Run water in every fixture you rarely use. Guest showers, spare bathroom sinks, a laundry sink and any floor drain. Let each run for a short while to refill its trap.
2. Check the toilets. Look at the base of each one. Gently push the bowl side to side. A toilet that rocks, or has a damp or stained floor around its base, may have a failed wax seal letting sewer gas out.
3. Look under the sinks. Check for water, a loose slip nut or a trap that has come apart.
4. Check the washing machine drain. A standpipe without a proper trap, or a hose pushed too far in, can let gas back up.
5. Note when it happens. Write down whether the smell is stronger after flushing, after rain, on windy days or when the AC kicks on. That pattern helps the plumber.

If the smell fades within a day of running water through the quiet fixtures, a dry trap was the cause, and running them now and then will keep it away.

When to stop and call a pro

Call a plumber if the sewer smell in the house does not fade after refilling the traps, or comes with any of these:

• Gurgling from drains or toilets when other fixtures are used
• Slow drains in more than one room
• Sewage backing up into a tub, shower or floor drain
• Wet patches, sunken spots or lush green grass along the line in the yard
• A smell inside a wall or under the floor, away from any fixture

Those point at a vent or line fault, and a backup can turn into a health problem quickly. Do not go onto the roof to look at vents. Do not open the sewer cleanout outside. If the line is full, sewage can come out of it under pressure. Keep children and pets away from any sewage and air out the room.

Dry traps, vents and line faults: which is urgent

Dry traps are not urgent. Refill them, and the smell should clear.

Vent problems are a priority but rarely an emergency. Vent pipes run through the roof and let sewer gas out above the house. If a vent is blocked by debris or a nest, or an air admittance valve under a sink has failed, gas can be pushed out through the traps instead. Drains often gurgle too.

Line faults are the urgent ones. A cracked pipe under the slab, a broken joint in a wall, or a blocked main line can all let sewage and gas into the house. If the smell comes with backups or wet spots, call straight away.

Florida specifics worth knowing

Many homes in Broward County sit on a concrete slab with the drain lines under the floor. In older houses those lines are often cast iron, which corrodes over time. A crack under the slab can let sewer gas rise through gaps in the floor or around pipes without any water showing. Homes on septic tanks can also give off a smell when the tank is full or the drain field is struggling, especially after heavy rain.

Second homes and seasonal homes are prone to dry traps. A house left closed through the summer often greets you with a sewer smell in the house when you come back, simply because the traps have dried out.

How One Call fits in

One Call Home Pros is a connector, and the plumbing licence belongs to the professional who does the work. Tell us where the smell is, when it is strongest and whether any drains are slow or backing up. We match you with a vetted local plumber, licensed and insured for drain work. The plumber traces the source and explains what is causing it before any work starts. The plumber can run a camera inspection when it is needed, or suggest a smoke test, to find a hidden crack. One Call arranges the visit and stays with the job.

You pay One Call, and One Call pays the plumber, so ask what the price covers up front. See drain cleaning for more, or the pages for drain cleaning in Sunrise, Tamarac and Hollywood.

Get the smell traced

If refilling the traps did not clear it, or the smell comes with gurgling or backups, tell One Call what you are noticing. We connect you with a vetted, licensed local plumber.