Drains and toilets · Naples and Campania
Sewer smell in the bathroom: where it comes from and how to get rid of it
A sewer smell in the bathroom almost always has a precise and nearby cause: a trap left without water, a dirty floor drain, a seal that no longer closes. You find it by elimination, one drain at a time, and very often you can identify it yourself on a video call, with no visit needed.
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If you are not sure it is a sewer smell and you fear it could be gas, especially near the boiler, hob or gas meter, do not take risks. Do not switch lights or appliances on or off, do not use flames, open the windows, close the gas tap at the meter if you can do so safely, leave the house and call your distributor's gas emergency line from outside (toll-free number on the bill; for Italgas 800 900 999, free 24 hours a day) or 112. This is not a case for a video call.
Recognise the problem
- The smell is noticeable on entering the bathroom, especially after a few days away
- The smell rises from the sink or bidet even when they are clean
- The shower drain smells, more when it is hot
- The sink gurgles when the neighbour upstairs empties
- The base of the toilet smells of sewage
The most common causes
- 1
Dry trap
Every drain has a trap, a curve that holds a little water: that water acts as a plug against sewer odours. If a drain goes unused for weeks, like the bidet in a guest bathroom or the floor drain, the water evaporates and the plug disappears.
- 2
Dirty shower drain
Under the shower grate hair and soap form a film that rots. In many shower trays the trap is also low and shallow, so it dries out quickly.
- 3
Sink overflow
The hole at the top of the sink basin collects splashes of soap and toothpaste that nobody ever rinses. Over time it becomes a source of bad smell.
- 4
Toilet seal towards the drain
If the seal between bowl and drain does not close well, the smell gets through even without visible water leaks.
- 5
Stack vent
The building's drain stack needs a vent, a pipe that rises to the roof and lets air in. If it is missing or blocked, when someone flushes on the upper floors the stack sucks water out of the traps in the flats.
What you can safely check yourself
- Run water for a minute in every bathroom drain, even those you never use, including the floor drain if there is one. If the smell goes away within an hour, it was a dry trap.
- Remove the shower grate and wash the drain and the little bell underneath with gloves, a brush and hot water.
- Pass a bottle brush through the sink overflow hole, with hot water and a little washing-up liquid.
- To find the guilty drain, plug them all with a stopper or a wet cloth and reopen them one a day: the smell returns when you open the right one.
- Before a long holiday, pour a glass of water into every drain and close the plugs: the trap stays full longer.
Never open the boiler or the gas water heater, and always switch off the power before touching an electrical appliance. If in doubt, call us.
When you need a technician at home
- The smell stays with all the traps full and clean
- The traps empty with a gurgle when the neighbours flush
- The base of the toilet smells and the seal must be redone
- A drain was installed without a trap, for example the washing machine one
Why a trap empties
The simplest case is evaporation: in summer, with the heat of Naples, a shallow trap can dry out in a few weeks. It happens above all in homes shut up for the holidays and in guest bathrooms.
The sneakier case is suction. When a lot of water goes down the stack, for example when the neighbour upstairs flushes the toilet, if air does not enter through the vent the stack takes it wherever it can find it: from the traps. You hear a gurgle, the trap empties and soon afterwards the smell arrives.
In this second case filling the traps is not enough, because they empty again. On some drains an air admittance valve can be fitted, a small device that lets air into the pipe without letting odours out. If the fault is in the stack vent, the condominium must be involved.
Shower drain that smells
The shower is the drain that gets dirtiest and is cleaned least. Taking off the grate once a month and pulling out the little bell underneath, if there is one, solves most odour problems.
If the smell stays with a clean drain, the trap may be too shallow, as happens in some flush-to-floor shower trays, or a fitting under the tray may not be properly sealed. On video we assess whether the drain needs to be taken apart.
Bicarbonate and vinegar, or enzyme drain products, help keep the pipe clean but do not replace a trap full of water. If the smell always returns, the cause must be found, not covered up.
Want to know what it is first? Show us
On a video call we go round the bathroom drains with you: sink, bidet, shower, toilet and any floor drain. We tell you which to fill, which to clean and how to plug the others to isolate the smell. If the cause is the stack vent or the toilet seal, we work out what the visit needs.
Video consultation, up to 15 minutes: €9.90 (€14.90 on Sundays), deducted from the bill if we then come to your home.
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Frequently asked questions
Why do I smell sewage in the bathroom only now and then?
Often it coincides with a neighbour flushing or with the hottest days. In the first case the trap is being sucked out, in the second it is evaporating. Note when it happens: on a video call it is a valuable clue.
Why does the sewer smell come from a clean sink?
Look at the overflow and the trap: the first holds soap residue, the second may have emptied or be dirty. If the sink gurgles as it drains, there is also an air problem in the pipe.
Is a sewer smell dangerous?
A sewer smell from a dry trap inside the home is usually a matter of comfort and hygiene more than safety. But if you are not sure it is sewage and it could be gas, go outside, do not touch switches and call the distributor's emergency line or 112 from outside.
Do I need a plumber for a sewer smell?
Often not: filling and cleaning the traps solves many cases, and on a video call we guide you. A visit is needed if the toilet seal must be redone, if a trap is missing or if the problem is the stack vent.
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