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Sewer Smell/Plumber says not vent -- A/C cause?
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Posted by simgirl (My Page) on Sat, Jul 7, 07 at 11:42
| We've got a 5-year old house that smells strongly of sewer gas in the center of the house, mostly in humid, hot weather. We've had the plumber out several times. He has checked the traps, fixed a missing cap on the dehumidifier trap and also performed a "peppermint test" to check for leaks on the main vent. The peppermint test involves putting peppermint oil down the suspect vent pipes to check for leaks. No dice with any of these tests. Not only do we smell no peppermint in the house (just attic, where it was released), we still smell the sewer gas. The plumber now says it's not the plumbing, but probably something with HVAC. Our A/C sits directly in the middle of the house, next to the sump pump basin. None of our neighbors with the same arrangement seem to have this problem. We're now at a loss as to which contractor to call next -- HVAC? Another plumber? House inspector?? |
Follow-Up Postings:
RE: Sewer Smell/Plumber says not vent -- A/C cause?
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| Do you have drains in the basement? Have you filled the traps in them with water? |
RE: Sewer Smell/Plumber says not vent -- A/C cause?
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Also have the HVAC system checked out if you find nothing else. There could be a leaky return area.
Do you have carpeting that may have gotten wet? |
RE: Sewer Smell/Plumber says not vent -- A/C cause?
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| There is one drain/trap in the basement; it gets regular use (bathroom), so should have water in it regularly. Thank you for your replies. There is no moldy carpeting that we are aware of. Additionally, the smell is definitely sewer, not mold (also, people with mold allergies in the house, no allergic reactions correlating to the smell.) The vents go through the roof (they do not terminate in the attic) The smell sits heavily in an area that is devoid of air vents but does have a return present, as it is above the a/c unit in the basement. If it is the HVAC, where could the smell be coming from? The sump pump? |
RE: Sewer Smell/Plumber says not vent -- A/C cause?
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| If you have a floor drain, a toilet in the basement won't necessarily keep that floor drain trap filled with water. Check that drain. I don't think a sump pump pit would smell, but you could put some clorox in the pit and see if it makes a difference. |
RE: Sewer Smell/Plumber says not vent -- A/C cause?
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| There is no floor drain that we are aware of; the basement is fully finished with two sewer clean-outs that are nowhere near the HVAC system (across the room, no smell near/above them anywhere in the house). Our sump pump rarely runs, we've maybe heard it twice in 5 years. Would that make a difference? |
RE: Sewer Smell/Plumber says not vent -- A/C cause?
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| This is off the top of my head but just a thought. Where is the condensation drain line for your AC unit draining to? It probably should not be draining directly to any of the household waste lines ie sink drains downstream of the sink trap. If it is, then the negative pressure in the drain line when the air handler is on could be sucking sewer gases right into the ventilation system. The drain line should have a j trap and be routed to exit the house via direct drain or condensate pump. Also check your overflow pan to make sure accumulated overflow water has not started your own private wetland preserve. Dave |
RE: Sewer Smell/Plumber says not vent -- A/C cause?
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| Dave, you might be on to something. Hmmm. I do not know where the overflow pan drains to. It's difficult to access, behind the unit and under stairs, but we can check. Thanks! Any other ideas pop out to anyone? |
RE: Sewer Smell/Plumber says not vent -- A/C cause?
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| Just to clarify, the condensation drain from the air handler is the primary way that moisture is removed from the from the unit. The condensation runs down the cooling coils to a trough and then to the drain line. IF that line becomes plugged for some reason, the water will usually overflow to a pan underneath the unit. That pan in turn will have a drain line. Or in a basement it may not. In my attic units the overflow drain comes out over the deck where it can be seen. I have seen it dripping once and it was because the primary line had become plugged. Note: If you find a problem and have to route the line outside , Make sure you get the water, (all water!)AWAYAWAYAWAY from the house foundation or you will be having different problems. |
RE: Sewer Smell/Plumber says not vent -- A/C cause?
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| Once the primary drain blocks with scum and you're on the second pan drain, it's only a matter of time till you have a flood. The best bet is to have a float with a cut-off switch in the pan to prevent this flood. It will shut down the unit before that happens. |
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