Sewer smell in the house? Try a jug of water first.
We dig up sewer lines for a living and the honest first answer is still that it is probably a dried-out trap, and free to fix. Here is how to rule that out, and how to tell when the smell really is coming from the pipe in the ground.
Most sewer smells in a house are a dry trap. Every drain holds a plug of water that blocks sewer gas, and a drain nobody uses loses it to evaporation in a few weeks, leaving an open pipe to the sewer. Pour a jug of water down every unused drain, including the basement floor drain, and give it a day. Three things point outside instead: gurgling or slow drains, a smell that worsens after heavy rain, or a smell strongest along the line and the foundation rather than at one fixture. Those are worth a camera inspection, $200 to $800, which either finds a crack, roots, a belly or a separation, or tells you the pipe is sound and the problem is indoors.
Inside the house, and a plumber's work
These are the common ones, and the first is the most common cause of all.
A trap that dried out
Every drain holds a plug of water that blocks sewer gas. A guest bathroom, a basement floor drain, a utility sink nobody uses: leave it a few weeks and that water evaporates, and the drain becomes an open pipe to the sewer. Pour a jug of water down it. This is the most common cause of a sewer smell in a house and it costs nothing to rule out.
A failed wax ring under a toilet
A toilet that rocks slightly, or a smell that is worst right at the base of one, usually means the seal between the toilet and the floor flange has gone. It is a plumber's afternoon, not an excavation.
A blocked or frozen vent
The stack through the roof lets the system breathe. Blocked by a nest, ice or debris, drains gurgle and siphon their own traps dry, so the smell moves around the house and comes back after every big drain. Gurgling is the tell.
A dry or missing floor-drain trap primer
Basement floor drains in finished spaces are often fed by a small primer line to keep the trap full. When it fails the trap dries out on a schedule, which is why the smell seems seasonal.
Outside in the ground, and ours
These share a pattern: the smell comes with drainage behaving badly, or it tracks the weather, or it is worse outdoors than at any one fixture.
A cracked or offset lateral
The pipe from the house to the main can crack, shift at a joint, or separate. Gas escapes into the soil and finds its way up, often strongest along the foundation or in the basement after rain, because wet ground pushes it indoors rather than letting it dissipate.
Roots in the line
Roots enter at joints, hold solids, and the line stops scouring itself. Usually the smell comes with slow drains and gurgling long before it becomes a backup.
A belly in the run
A section that has settled holds standing waste instead of passing it. It smells, it collects, and it is the reason a line that has been cleared twice still misbehaves.
An abandoned line that was never capped
Old laterals, a removed outbuilding, a septic tank taken out of service and left open to the house drain. More common on older properties than people expect, and the smell has no obvious source inside.
A septic system that has stopped working
Odour around the tank or the field, wet ground, grass greener over the disposal field. That is a different problem from a lateral and it gets looked at differently.
The test that settles it
A camera inspection runs the line and shows what is actually there. It is worth doing before anybody digs and before anybody replaces a fixture on a hunch, because the two outcomes are both useful: it finds the fault and locates it, or it clears the lateral and sends you back inside with the search narrowed to traps, vents and seals.
If the smell comes with water backing up rather than just odour, that is a different and more urgent page: sewer backing up. If the property is on septic, start with a septic inspection.
What we do, and what we do not
We are an excavation and underground utility contractor. The lateral, the roots, the bellied or collapsed run and the abandoned line nobody capped are ours. Traps, wax rings, vents and anything inside the wall are a licensed plumber's work, and on jobs that need both we bring a plumber in and work alongside them rather than pretending the line between the two does not exist. See sewer & water line work.
What customers say about this work
We have a busy restaurant in Stanhope, Shakey Jakes. We had a water main break that needed 50 ft of digging. They started at 2 am in freezing cold weather so as not to interfere with business. They did as they said and were very professional.
I had two recent emergencies and James and his team responded the same day. Immediate callbacks even though they were busy, and the pricing was very fair. And he volunteers as an EMT. Five star ++ rating for sure.
Common questions
Why does my house smell like sewer?
Most often a dry trap. Every drain holds water that blocks sewer gas, and a drain nobody uses loses that water to evaporation in a few weeks, leaving an open pipe to the sewer. Pour a jug of water down every unused drain, including basement floor drains, and wait a day. If the smell goes, that was it. If it comes back to the same spot, or comes with gurgling and slow drains, the problem is further out.
Is sewer gas in a house dangerous?
Treat it as worth fixing rather than as an emergency in most cases. Sewer gas is mostly methane and hydrogen sulphide, and the concentrations behind a normal household smell are an irritant rather than a hazard. The exception is a strong, persistent smell in an enclosed space such as a closed basement or a crawl space, which is worth ventilating and taking seriously. If anyone has headaches or nausea that clear when they leave the house, stop diagnosing and get out.
How do I know if the smell is my sewer line and not something inside?
Three signs point outside rather than in: the smell arrives with gurgling drains or drains that empty slowly, it gets worse after heavy rain, or it is strongest outdoors along the line and near the foundation rather than at one fixture. Any one of those is worth a camera. A smell confined to one room, especially at a toilet base or an unused drain, is almost always inside.
What does a camera inspection cost?
$200 to $800, driven mostly by how much line there is and whether there is a usable cleanout. It is the test that ends the argument: it either shows a crack, roots, a belly or a separation, or it shows a sound pipe and tells you to stop digging and call a plumber. Either outcome is worth more than another round of guessing.
Do you fix the smell?
We fix the outside causes: the lateral, roots, a bellied or collapsed run, an abandoned line that was never capped. Traps, wax rings, vents and anything inside the wall are a plumber's work, and we will tell you that rather than sell you a dig. When a job needs both, we bring in a licensed plumber and work alongside them, which is how the sewer work on this site runs anyway.
Why is it worse when it rains?
Because saturated ground stops sewer gas dispersing into the soil and pushes it toward the easiest opening, which is often your basement. A smell that tracks the weather is a reasonably strong hint that gas is escaping underground rather than from a fixture indoors.
Ruled out the traps and it still smells?
We camera the line and tell you what is actually wrong, including when the answer is that you need a plumber and not us.
Call 862-268-2510