Hello,
we have recently encountered the following problem:
when doing laundry, the entire utility room smells like sewage or a chemical, chlorine-like odor. This only happens once the washing machine starts rinsing, meaning when the water is being pumped out.
Some curious and completely puzzling points for me are:
- a new washing machine was purchased, but the problem persists
- it only occurs with a specific wash cycle, which is used most often
- a new built-in trap was installed, but the problem remains the same
- a camera inspection of the drain pipe showed no issues
We have lived here for almost 15 years. The system was newly installed back then and worked fine until last year.
Our plumber has already been here but has no solution.
Is it possible that the machine is drawing water from the sewer during pumping? Even though there is a trap?
I would appreciate any ideas...
Best regards,
Stefan H.
we have recently encountered the following problem:
when doing laundry, the entire utility room smells like sewage or a chemical, chlorine-like odor. This only happens once the washing machine starts rinsing, meaning when the water is being pumped out.
Some curious and completely puzzling points for me are:
- a new washing machine was purchased, but the problem persists
- it only occurs with a specific wash cycle, which is used most often
- a new built-in trap was installed, but the problem remains the same
- a camera inspection of the drain pipe showed no issues
We have lived here for almost 15 years. The system was newly installed back then and worked fine until last year.
Our plumber has already been here but has no solution.
Is it possible that the machine is drawing water from the sewer during pumping? Even though there is a trap?
I would appreciate any ideas...
Best regards,
Stefan H.
O
Oberhäslich7 Mar 2025 20:10Stefan H. schrieb:
The external siphon has already been replaced. The real question is why the draining process isn’t the same for all wash temperatures? Shouldn't the draining be identical every time? Because each program uses a different amount of water, the amount drained varies accordingly. This is just a theory, but it makes the most sense to me since the washing machine is new and the drain is fine. It probably occurs more with intensive programs (cotton, higher temperature, etc.).
W
wiltshire7 Mar 2025 22:43When did the bad smell first occur? After a vacation or a longer break with the machine turned off (door and detergent drawer closed), a foul odor can develop. If this is the case, simply disassembling the machine once and thoroughly cleaning it mechanically is enough to fix the problem. These machines are quite simple. It can be done within 2-3 hours.
Since a new machine was installed after the odor issue occurred, and the smell still persists, with the odor not coming specifically from the machine but present throughout the laundry room, yet happening in sync with the machine cycle and only during certain programs, @Oberhäslich's conclusion seems plausible that it is related to the volume of water being drained. At a certain amount, a siphoning effect occurs in the building’s wastewater system that likely empties a trap in the laundry room.
A possible solution, to my knowledge, is installing an air admittance valve near the washing machine connection or increasing the diameter of the wastewater pipe from the washing machine to the main drain pipe. Also, it’s worth checking whether the branch connections to the soil pipes are installed at a 45° angle (which is no longer common; today, 87.5° is preferred to prevent siphoning effects).
I’m not a professional, just an experienced layperson.
A possible solution, to my knowledge, is installing an air admittance valve near the washing machine connection or increasing the diameter of the wastewater pipe from the washing machine to the main drain pipe. Also, it’s worth checking whether the branch connections to the soil pipes are installed at a 45° angle (which is no longer common; today, 87.5° is preferred to prevent siphoning effects).
I’m not a professional, just an experienced layperson.
S
Stefan H.9 Mar 2025 09:02Tolentino schrieb:
Since a new machine was purchased after the odor issue arose and the smell continues to persist, and because the odor is not specifically coming from the machine but is present throughout the laundry room—although it coincides with the machine’s operation and only with certain programs—@Oberhäslich’s conclusion makes sense that it is related to the amount of water being drained. At a certain volume, a vacuum is created in the house’s wastewater system, which likely siphons the trap dry in the laundry room.
As far as I know, installing a ventilation valve near the washing machine connection or increasing the diameter of the wastewater pipe from the washing machine to the main sewer line can help. Also check whether the branch connections on vertical drain pipes are installed at a 45° angle (which is no longer standard, as 87.5° is now preferred to prevent siphoning effects).
I am not an expert, just an experienced amateur.You’re right, it depends on the laundry and therefore the amount of water. I once tested by just washing a winter jacket, and there was no smell, but after a full load the odor came back.
Similar topics