Start by finding which spot smells worst
Stand in the bathroom with the door closed for a minute, then move your nose toward the sink, the tub, the shower drain and the toilet base in turn. The smell is rarely spread evenly. One spot is nearly always stronger, and that spot is your first clue.
Next, ask when it happens. A smell that shows up only after a long stretch away from home is different from one that appears every time the washing machine drains or someone showers upstairs. Write down what you notice, because a plumber can use those details over the phone.
Common causes, sorted by how often they turn up
Every drain in your home has a curved section called a trap that holds a plug of water. That water blocks gas from the sewer. If the water is gone, or a vent is blocked, gas gets through. The table lists the usual suspects and the first thing to check for each.
| What you notice | Likely cause | First check |
|---|---|---|
| Smell from a floor drain or a seldom-used tub | Dry trap | Pour water down it and see if the smell fades |
| Gurgling sounds plus smell | Blocked or partly blocked vent | Look at the vent pipe on the roof for nests or debris |
| Smell around the toilet base | Failed wax ring or loose flange | Check for rocking and damp flooring |
| Smell in several rooms and slow drains | Sewer line problem | Run other fixtures and note what else gurgles |
| Musty smell, not quite sewage | Mold or a drain film | Clean the overflow and stopper area |
Treat the table as a starting point. Two causes can overlap, and a smell that fits one row may still need a second look.
Smell still there after the simple checks? Call us and describe what you notice.
(732) 466-1098Who handles the sewer outside your property
Where your own pipe ends and the public sewer begins depends on the town and the utility. In Highland Park, a Middlesex Water subsidiary named Utility Service Affiliates operates the borough water and wastewater system, so a main-line backup outside the home goes through that operator. If you live in Highland Park, call them as well as a plumber when the street sewer is the suspect.
We have not verified the sewer operator for every New Brunswick block. Ask the city or your landlord who maintains the sewer main on your street. Neighbors in East Brunswick should ask their own township the same question, because the rules were not verified for this post.
Source: Middlesex Water Company page on Utility Service Affiliates, Highland Park
The dry trap is the simplest fix and the most overlooked
A guest bathroom, a basement shower or a floor drain can sit unused for weeks. The water in the trap slowly evaporates, and the gas comes straight up. Running water for about a minute refills it. If the smell fades soon after, you found it.
For a drain you rarely use, a small amount of water every few weeks keeps the seal in place. A spoonful of cooking oil on top of the water slows evaporation in floor drains. If the smell returns within a day of refilling, the trap is probably not the whole story.
Vent trouble: when drains gurgle and smell together
Plumbing vents let air in behind the water so drains empty smoothly. They also carry sewer gas up and out above the roof. When a vent is blocked, drains gurgle, traps can be pulled empty, and gas works its way indoors.
You can often see the outside end of a vent from the yard. Leaves, a bird nest or ice in cold weather can plug it. Do not climb onto a roof to clear it. A plumber can do that safely, and a blocked vent that clears easily may still hide a crack further down the pipe.
Seals, wax rings and the toilet base
A toilet sits on a wax ring that seals it to the drain flange. If the ring fails, you may notice a smell at floor level and sometimes a stain around the base. A toilet that rocks even slightly is worth attention, because the seal can leak sewage water under the flooring over time.
Stop using that toilet if the floor feels soft or damp near it. Sewage water on subfloor material is a cleanup issue as well as a plumbing one. For a toilet that is loose, see our toilet repair page for what the work involves.
Resetting a toilet in the same spot is a like-for-like job, and the state Department of Community Affairs code alert says swapping a fixture without changing the piping needs no permit or inspection. It must still meet code. If the smell traces to the drain line itself, that is plumbing work for a licensed plumber.
Source: NJ Department of Community Affairs code alert, nj.gov/dca/codes/alerts/pdfs/OM_MW_03052018.pdf
When the smell points to the sewer line
If the smell appears in more than one bathroom, drains are slow throughout the house, or you hear gurgling when the washer runs, the problem may sit in the main line. Roots, a bellied section, a crack or a buildup of grease and paper can all cause it.
A camera inspection is the direct way to find out. It shows the pipe from the inside, so nobody has to guess or dig first. Our sewer inspection page explains what a camera run shows and what usually follows if it finds damage.
Safety steps while you wait
- Open a window and run the exhaust fanAir movement thins out any gas in a small room. Leave the room if you feel dizzy or get a headache.
- Refill traps with waterRun each sink, tub and floor drain for about a minute. This costs nothing and rules out the simplest cause.
- Stop using a fixture that backs upIf water or sewage rises in a drain, stop running water into that line and call for help.
- Keep ignition sources away from a strong smellIf the odor is more like gas than sewage, leave the building and call the gas utility or 911 before anything else.
- Skip chemical drain cleanersThey can damage pipes, they do not cure a vent problem, and they are hazardous for the plumber who works on that line next.
Smell in the night or on a weekend
A strong sewage smell with water backing up is an urgent matter, and our dispatch line takes calls 24/7. While you wait, stop using the affected drains, keep children and pets away from standing water, and ventilate the room.
If the smell is mild and steady, it can usually wait for a same-day appointment when available. Tell the person on the phone which spot smells strongest and whether any drain is slow. That helps decide how fast to send someone.
Frequently asked questions
Small amounts usually cause only a bad smell, but sewer gas can cause headaches or nausea in a closed room. Ventilate, and leave if you feel unwell. A smell that seems more like natural gas means leave and call the gas utility or 911.
A smell that comes and goes often follows water use. A dry trap, a vent that clogs in certain weather or a drain that gurgles when the washer runs can all behave this way. Note the timing and share it when you call.
Refilling traps, cleaning the stopper area and checking a vent from the ground are safe homeowner steps. Anything involving the toilet seal, the roof or the main line is a plumber's job.
Yes. Our dispatch line is open 24/7. A smell with sewage backing up gets treated as urgent, and a mild smell can often be booked for a same-day appointment when available.
Tell us which fixture smells worst and whether drains are slow. Call (732) 466-1098.
It often can, when the problem sits in the drain line. A vent crack or a failing toilet seal may need other checks. Ask for a clear price before work starts so you know what each step involves.