Collapsing building © Daniel FriedmanSewer Gases / Septic Odors Passage Through Electrical Conduit
How septic or sewer smells may enter a building through electrical wiring

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Sewer gas leak sources, sewer or septic gases through conduit or ducts:

This article describes the detection and repair for sewer or septic gases & smells that are traced to passage through electrical conduit, open piping, or HVAC duct systems.

We describe how odors may be traced back to electrical wiring, conduits, or panels & sub panels, and how people stop that odor passage.

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Septic & Sewer Gases & Odors from Electrical Conduit, Open Pipes or Similar Passages

Reader Question: How do I Seal a Septic Gas Leak Entering the House Through Electrical Conduit?

Question: Does contain a section on how to properly seal conduit used for septic tanks and pumps?

The [] web site is fantastic! There’s a ton of info on septic systems and septic odors.

I have a septic tank and pump station (sewage leaves house and goes into original septic tank, then goes to a second tank with filter, and then goes to a pump, which pumps to leach field). The pump station has a vent (which does not appear to be clogged).

I clean the [septic] filter a few times a year (the plastic type that you pull out, rinse off, and re-install). The pump station conduit runs into my house. I’m assuming the conduit from pump station to the house must not be properly vapor sealed as I get sewer odor at electrical junction box (it took me quite a while to figure out where the odor was coming from).

The [septic] odor very consistently tracks to the filter cleaning cycle. Immediately after cleaning the filter there is no odor for the first few months, and then eventually the odor becomes noticeable and continues to become stronger and stronger until I clean the filter ... after which the odor goes away for another few months and the cycle repeats.

I’m not certain I fully understand why this occurs, but the cycle is consistent. The plus side is I always know when the septic tank filter needs to be cleaned. However in addition to the unpleasant odor that I smell when it’s time to clean the filter, I’m concerned about having septic gases in the electrical conduit.

Does the web site contain a section on how to properly seal conduit used for septic tanks and pumps? - M. & P. C.

Reply: Here we add advice on sealing leaky electrical conduit on septic pump systems - below

A competent onsite inspection by an expert, or maybe in this case just an electrician, usually finds additional clues that help accurately diagnose a problem. That said, here are some things to consider:

What a fabulous detective job you've done, Thank you. I will be sure to add this odor source to the septic odor source diagnostic list [above]. Indeed we have discussed other reports of unanticipated air movement through electrical conduit - in Roger Hankey's article see section "Water Entry into Electrical Panel Case #3 - Negative Air Pressure & Moisture Condensation"

Also see Back drafting & Sewer/Septic Odors.

But we haven't previously discussed sewer gas or smells moving through conduit regarding septic systems or in your case septic pump systems. Here are two suggestions:

Repair Steps for sewer gases from remote pumping station

Reader comment:

In Vermont this winter, frost is deep. Our tank for pumping spill over waste water from the settling tank to a sand mound is more than 100 feet from the house. We have a plastic underground conduit running from the house to the pumping tank to provide electricity to the pump.

The pumping tank is buried under a dense and heavy snow/ice mound and has no ability to breath and let gas escape. It has no vent. I detected an ever increasing sewer gas (rotten egg) smell at the electrical box where the conduit pipe comes into the house in our basement.

Putting my nose by the conduit pipe end gives an overwhelming rotten egg smell. Even with functioning roof vents and wet traps (no smell there) sewer gas has found a least resistance path into the house. Immediate solution was to spray foam into the conduit.

Tomorrow I will dig the ice snow around the manhole cover in the pumping tank and give it a small opening to release gases. - R.K. 3/14/2014


This is a helpful report, R., and not the first time we've heard of sewer gases making their way back into a building through electrical conduit. I think you've got the right approach; I'd just add that when weather permits, on the pump end you might want to inspect to be sure that the conduit is sealed there too, against water entry as well as gases.

You may also want to check METHANE GAS SOURCES - other sources of methane gas in and around buildings

Watch out: we warn in all sewer or septic gas odor articles that because sewer gas contains methane gas (CH4) there is a risk of an explosion hazard or even fatal asphyxiation.

Sewer gases also probably contain hydrogen sulfide gas (H2S) (HYDROGEN SULFIDE GAS). In addition some writers opine that there are possible health hazards from sewer gas exposure, such as a bacterial infection of the sinuses (which can occur due to any sinus irritation).

Depending on the sewer gas source and other factors such as humidity and building and weather conditions, mold spores may also be present in sewer gases


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