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Sewer smell

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SlamDunk
SlamDunk Member Posts: 1,601
I have an odd problem. Just now, and once before about six months ago, my basement and house was temporarily overwhelmed with a sewer odor. It goes away as quickly as it arrives. No ruptures in pipes above ground, and no problems draining. Any ideas? I had a plumber look around and he found nothing.
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  • Jamie Hall
    Jamie Hall Member Posts: 23,675
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    dry trap somewhere? Basement floor drains are often overlooked...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    mattmia2ethicalpaulSlamDunk
  • SlamDunk
    SlamDunk Member Posts: 1,601
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    Thanks for responding @Jamie Hall .the main sewer line doesnt have a trap. Just goes into the earth. Just traps at fixtures in house. I dumped a gallon of ammonia down the drain but didnt smell it anywhere else. The sewer smell is already gone. Odd.
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,391
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    Hi, A dry trap would also be my first thought. Sometimes you get a strong smell from the shower drain. If that's when you get the odor, try putting plastic or a wet towel over the drain before turning on the water and see what happens. Another smelly place can be any sink overflow. Pouring hydrogen peroxide into the overflow can help.

    Yours, Larry
  • Alan (California Radiant) Forbes
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    You may have a trap that’s not vented properly. Every now and then the trap seal is sucked out after it drains. 
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    SlamDunkHomerJSmithZman
  • Derheatmeister
    Derheatmeister Member Posts: 1,572
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    Had a very difficult one once...The sheetrock guys screwed the sheetrock to the pipe... took years to figure out.
    Empty traps are mostly the issue especially in dry enviroments such as Colorado or Utah
  • Mad Dog_2
    Mad Dog_2 Member Posts: 7,255
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    Yes..open pipe somewhere down there.  Could be a rotted vent pipe well above the water 💧 line....buried in a wall?  Mad Dog 🐕 
  • mattmia2
    mattmia2 Member Posts: 9,981
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    Mad Dog_2 said:

    Yes..open pipe somewhere down there.  Could be a rotted vent pipe well above the water 💧 line....buried in a wall?  Mad Dog 🐕 

    although rot usually doesn't happen above the wet part. more likely some sort of shifting or splitting if it is up high
  • mattmia2
    mattmia2 Member Posts: 9,981
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    then there are vents that just plain were never run outside. maybe just the right combination of usage so umm..waste remains in the pipe close to the house
  • Mad Dog_2
    Mad Dog_2 Member Posts: 7,255
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    I politely disagree Matty.  Sanitary vents way out of the water flow rot all the time especially in large and tall, commercial buildings.  Galvanized does it the most, but Cast Iron will do it too.  The methane gases and other smelly elements contained in it can be pretty corrosive.  Mad Dog 🐕   
  • MikeL_2
    MikeL_2 Member Posts: 506
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      When the alleged sewer smell is present I suggest opening the main drain clean out plug to take a whiff and see if the odors match. In my experience sanitary sewer systems can be less prone to producing offensive odors compared to a private system with a septic tank.
       A peppermint test can help find an issue with a dwv system. 
        I have traced intermittent offensive odor problems to a variety of sources including:
         Custom mud shower floors with no pre pitch below the pan & blocked weep holes.
          Rotting critter bodies in attics,  walls, floors, & ceilings.
           Tiny propane & natural gas leaks.
            Lavatory overflow drains.
             Grease traps; purposeful or accidental.
            Stored pool chemicals.  
            Stored garden & plant supplements & fertilizer.
           Lawn mowers & other equipment with wet cell batteries.
           Sewage ejector tanks & seals, especially systems that include kitchen sink drains.
            In extreme instances of constant alleged sewer gas I've used temporary whole house traps to isolate the outdoor portion of a dwv system.....
            
       
    SlamDunk
  • Mad Dog_2
    Mad Dog_2 Member Posts: 7,255
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    Hydrogen Sulfide IS corrosive. Present in all DWV systems that convey raw sewage  Mad Dog 🐕 
    CLambZman
  • Jon_blaney
    Jon_blaney Member Posts: 322
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    Clothes washer!
    mattmia2SlamDunk
  • Mad Dog_2
    Mad Dog_2 Member Posts: 7,255
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    A smoke test us also very good .  You get one shot with a Peppermint test per day.  If you don't find the leak quickly, the whole room can smell peppermint. I've done both.  U can rent a smoke machine  mad dog
    SlamDunkrick in Alaska
  • SlamDunk
    SlamDunk Member Posts: 1,601
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    we flooded the sewer line with water and it dissipated quickly.    the odor starts in the basement and floats up.    it is more a boiler pit with large crawl space than a basement.  no traps down there.   The plumber’s smoke machine was broken but I might rent one myself.  we have been here 32 years and this is the second time this has happened in the past 12 months; both times at 8:30pm.  The onlything running is the dishwasher.  

    It would be easier to resolve  if I could still smell it but it is gone.     I’ll check the vertical stacks but if they were cracked, I should smell something now.     we are calling this a sewer ghost.   
    Mad Dog_2
  • Mad Dog_2
    Mad Dog_2 Member Posts: 7,255
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    I had one in our Village Hall.  Located w Oil of peppermint and smoke and a pipe camera 📷.   Problem.....Fireman had just made a huge built in trophy display case and they weren't disassembling it!  Told the janitor to stock up in Pine Sol and dump down drains every day.  Mad Dog 🐕 🤣 
    SlamDunk
  • JUGHNE
    JUGHNE Member Posts: 11,111
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    Jamie mentioned floor drain trap being dried up, you responded about whole house trap.

    Do you have a floor drain? And any AC condensate drain going somewhere?
    SlamDunk
  • mattmia2
    mattmia2 Member Posts: 9,981
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    The cooking lead acid battery can smell exactly like a sewer.
    HomerJSmith
  • Alan (California Radiant) Forbes
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    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    SlamDunk
  • SlamDunk
    SlamDunk Member Posts: 1,601
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    Wow. I hope that isnt my problem @Alan (California Radiant) Forbes

    Clothes washer as @Jon_blaney mentioned mightbe an issue. 30' run straight to sewer main and no trap. Shouldn't it be trapped? It is vented thru roof but from washer drain to sewer, no trap.
  • mattmia2
    mattmia2 Member Posts: 9,981
    edited July 2023
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    There should be a trap at the sink or standpipe and some sort of vent because 30 ft is far too long for a wet vent
    Mad Dog_2
  • SlamDunk
    SlamDunk Member Posts: 1,601
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    @mattmia2 I don't understand. Washer is nowhwere near a sink. I have to look up wet vent.
  • SlamDunk
    SlamDunk Member Posts: 1,601
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    Ok, looked it up and understand....washer drain taps into vent but drain pipe goes down @4' then slopes straight across to sewer main without a trap.
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,391
    edited July 2023
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    Hi @SlamDunk , Could you share photos of the washer hookup? Just maybe an air admittance valve could help here.
    Yours, Larry
    SlamDunkmattmia2
  • SlamDunk
    SlamDunk Member Posts: 1,601
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    @Larry Weingarten , at the moment, I cannot. But it resembles this:
  • PC7060
    PC7060 Member Posts: 1,245
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    I had several old cast iron sewer lines that split along the top. Cracks occurred on top of all the horizontal lines which carried hot water from bathtubs. I think the drain line flexed due to the hot and cold water I the the metal cracked. 

    The lines didn’t really cause odors unless a low pressure zone came over. Then it was baaaad. 

    Thankfully all the line replaced now.  
  • SlamDunk
    SlamDunk Member Posts: 1,601
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    JUGHNE said:

    Jamie mentioned floor drain trap being dried up, you responded about whole house trap.

    Do you have a floor drain? And any AC condensate drain going somewhere?

    I do not.
  • Alan (California Radiant) Forbes
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    That may very well be your problem @SlamDunk. Put a trap on that bad boy. 
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    Mad Dog_2SlamDunkrick in Alaska
  • Jamie Hall
    Jamie Hall Member Posts: 23,675
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    Is that really the configuration, @SlamDunk ? That puppy is going to smell from time to time --probably quite unpredictably. If that's a vent line you show going up from the washer, you can put a regular P trap on it. Otherwise, a P trap with an air valve such as you would use under an island sink will work.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    SlamDunkrick in Alaska
  • SlamDunk
    SlamDunk Member Posts: 1,601
    edited July 2023
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    That is how it is configured. The vent tee isbehind wall. I imagine it looks like sketch. Been like this for 22 years. I have to look up trap with air valve. I was thinking something like this:

  • SlamDunk
    SlamDunk Member Posts: 1,601
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    Looked it up. I understand! Thank you everyone. Hopefully, that is the only problem.
  • mattmia2
    mattmia2 Member Posts: 9,981
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    Is there a trap in the wall before the lateral at the bottom of the standpipe?
  • SlamDunk
    SlamDunk Member Posts: 1,601
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    mattmia2 said:

    Is there a trap in the wall before the lateral at the bottom of the standpipe?

    I hope not. I'm not a plumber but I wouldnt bury a trap behind a wall when I can expose it a foot lower in the crawl space. But, then again, if it is legal, it could be. It was permitted and inspected.
  • SlamDunk
    SlamDunk Member Posts: 1,601
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    line is not trapped.    But they did give me two clean out tees.   





  • SlamDunk
    SlamDunk Member Posts: 1,601
    edited July 2023
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  • hot_rod
    hot_rod Member Posts: 22,505
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    A P trap would be the best way, maybe add a 45 to vertical under the floor, trap then vent through roof, or air admittance valve on a 1-1/2 vent line.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    SlamDunk
  • JUGHNE
    JUGHNE Member Posts: 11,111
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    There is usually a P-trap below the washer box, in your case it would be inside the wall.

    The washer should drain into the trap, the trap into the vented drain line.

    If you put the trap after the vented line then the air vent will do no good as the system drains out as it is isolated from the system by the trap.

    I have been in basements where the sewer line if open does not have any smell of gas.

    Then some where you take a CO plug out and just about pass out.

    What is that box with the round duct on it....a dehumidifier?
    SlamDunkrick in Alaska
  • HomerJSmith
    HomerJSmith Member Posts: 2,511
    edited July 2023
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    When was your house built? What is the material that that the waste pipe are composed of? In the early '80's ABS pipe was manufactured improperly and over time the pipe where it connected to the fitting cracked. There was a law suit settlement which you could find on the internet. Hydrogen sulfite gas is some times found in well water.
  • SlamDunk
    SlamDunk Member Posts: 1,601
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    hi,

    Ill pull washers drain pipe out and check.    worst case the line would be double trapped with an air vent.  the smell has to come from there.   that is near where we sit.    this addition was built in 2000.  The house, 1930.    it is charlotte pvc.   big round duct is dehumidifier.    i wanted dehum air vented further away.   Dont worry, it isnt suspended by straps.   it is mounted to wall with unistrut.   straps were to hold it in place.    I just left them.   
  • JUGHNE
    JUGHNE Member Posts: 11,111
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    The dehumidifier must drain somewhere.
    Could there be a drain/trap/riser pipe that could be passing gas?

    I have cut an access opening under a washer box and covered it will a return air wall grill, you could do this for inspection.
    (I did it because of a bad solder joint....yes, IIRC, it was the only one I ever had ;) )
    PC7060
  • SlamDunk
    SlamDunk Member Posts: 1,601
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    Oh, the dehumidifier drains into the sump. Eventually, sump pumps it to daylight.