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Basment Sewage Ejector pump vent smell

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Hello, I have an ejector pump tied into a two inch main line. The tank has its own dedicated vent. Upon discharge it is quite evident that I have a vent issue. sometimes the smell in my basement is strong and other times I can not smell it (smell only occurs directly after discharge). Not sure why but the smell seems to be more prevalent in the cooler months. I have a few fixtures in the basement and I try to ensure that the traps are full to eliminate the smell if im using the bathroom tied to the pump. At this point im wondering if my problem could be related to the fact that the pump discharges about 1.5 feet behind another 2inch drain line. Wondering if the pump is pushing and pulling gas as it rushes by?? This recently occurred to me when I think I heard water from this pipe rushing down shortly after the pump discharged. Seemed as if it was siphoning out but im not positive.... Im considering switching the two drain lines to see if this help the situation? This way the pump would discharge after this other line I am describing. Thank you for any assistance you can provide.
asked in Plumbing by fisher (120 points)
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1 Answer

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Hi Fisher,
If you can smell the sewer it must be (in most cases) open or opening somewhere in the basement area at the time your ejector pump drains the pit.
Some critical areas that can be responsible are:
  • Bathroom toilet around the base where the wax ring might not be providing sufficient seal
  • Basement floor drain if it has no trap, discharges into the pump’s tank below the waste water line (when the tank is full / before the pump is activated)
  • Poorly sealed sump pump tank / pit
  • Depending on the vent / sewer pipes material and their age, in case of cast iron and / or galvanized pipes, some might be corroded to the point where their walls have been breached and leaking sewer gasses.
  • PVC’s sometimes crack or separate at joints.
Siphoning shouldn’t happen unless there’s a clogged, missing or improperly designed / installed vent, or you have an “s” trap installed beneath one of the basement fixtures. If possible (and safe) you could check its roof termination for any issues (clogged with leaves, beehive, dead birds / rodents, etc.)
Switching the drain lines might resolve the sewer smell issue, however, in a properly designed and functioning plumbing system there shouldn’t be any sewer gas smell inside the house.
Please let me know how the investigation goes and if you have more questions.
answered by darekrudy (21,730 points)