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Thread: Awful smell from plumbing?

  1. #1
    DIY Junior Member teryl's Avatar
    Join Date
    May 2013
    los angeles, ca

    Default Awful smell from plumbing?

    We had a house built in Lake Arrowhead Ca, in 2007,the house is very high on the mountain,& ever since the house was ready to move in,there has been an odor that smells the house only when the winds are high.(smells like sulfur ) if there is no winds ,we don't smell it..
    we are on a septic tank,but not sure if this is where it is coming from, (septic tank is far from the house.)
    The master bathroom on the second floor is where it smells the worse,,and the bathroom on the lower level smells.... the contractor has no idea where the smell is coming from & has changed all the filters to charcoal, (this hasn't helped as well..)

    We have also had the original plumber come back as well and he says all the pipes are connected properly ..

    Do you have any suggestions ? or what could be the problem?
    thanks a bunch..

  2. #2
    DIY Senior Member bluebinky's Avatar
    Join Date
    Aug 2011
    Santa Clara, CA


    All guesses here, of course...
    Are you sure it's the plumbing?
    Check that all drains have water in their traps -- including floor drains.
    Check the air conditioner and/or furnace condensate drains. If they are connected to a drain, it must be indirectly (air gap or break) and then through a trap which is not allowed to dry out (not directly into a vent in the attic). If not, sewer gas can be drawn into the heating system. Probably not your problem since the smell is localized.

  3. #3


    If not used for a long enough period, the water in a trap will evaporate to the point that the water no longer seals the bend in the trap and sewer gases are admitted past the trap and out the fixture drain. A vacation home makes it more likely that the drains will have infrequent use, and being at altitude accelerates the evaporation. Incorrectly routed drains and vents can also cause water running at one fixture to evacuate the trap of another (toilets are a big offender - the rush of water from a flush can suck other traps dry if the line is not properly vented).

    But the wind seems to be key here. With a 2007 construction house, built for snow, it's probably extremely airtight. It could be that the (non-sewer) venting in your house is such that when the prevailing wind blows, it's creating negative pressure in the house, and this, in turn, is causing air to be pulled into the house through the drains (especially if you've got any dry traps).

    Next time you're testing
    -open some windows on the windward side to ensure the wind isn't creating a negative-pressure condition in the house (not in the room where you're getting the smell - the point is to equalize pressure in the house, not vent out the smelly rooms)
    -run water through all the drains to ensure the traps are flooded

    -No smell? Close the windows, wait a few minutes, then sniff around all the drains in the two bathrooms.
    -No smell? Flush the toilet in the upper bath (full flush), wait a few minutes, and do the sniff test.
    -No smell? Flush the other toilet (full flush), wait a few minutes, do the sniff test.

    If the smell returned upon closing the windows, you've got an open vent somewhere, being exacerbated by an airtight house. If you're POSITIVE all the traps were flooded (including furnace/ac condensate lines, and washing machine drain), I'd be looking for an open vent inside a wall or attic.

    If the smell returned after flushing either of the toilets, you've got a vent problem on one of the those lines. If you hear a gurgling at any nearby fixtures when you flush a toilet, that's a clear sign of poor venting.

    If you get the smell with all traps flooded and a windward window open, I'd guess you've got an open vent line inside a wall.

    One other obvious thing -- look under the bathroom sinks and verify that they all have a real 'P' trap (google it). No trap or an 'S' trap are both bad news (and would fit with the tight house/negative pressure scenario). It shouldn't have been built (and shouldn't have passed inspection) with anything but a P-trap; but if the apprentice did that room, and the inspector wasn't thorough, it could happen.

    One other possibility (kind of a stretch). If the vent on your septic tank admits air to the tank, and it's positioned relative to the wind such that positive pressure develops near the vent (wall, slope, hedge, etc, on the leeward side), the tank could become pressurized. Combine this with a low-pressure condition in the house, and your house becomes the vent for the septic tank. This could also apply if the tank vent isn't venting. If your traps and vents in the house are working, a pressurized tank shouldn't be an issue. But any problems with your venting would be magnified by a pressurized septic tank.

  4. #4
    DIY Senior Member Hairyhosebib's Avatar
    Join Date
    Jun 2010


    Pouring a small amount of vegetable oil in a floor drain will help keep water in trap from drying out.

  5. #5
    DIY Junior Member teryl's Avatar
    Join Date
    May 2013
    los angeles, ca


    Thanks so much for taking the time & this advise .. wish me luck..

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