Mystery Smell - What could it be, how to fix?

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Mystery Smell - What could it be, how to fix?

Max T.
Investor · Philadelphia, PA · Member since 2015 · 3k+ posts · 3k+ votes

The property is a rowhome, partially connected on both sides.

The smell is strongest on the RIGHT side of the house towards the front inside the finished basement.

This is the side that has access to the outgoing waste line.

I was able to determine this by opening up several access panels in the finished basement walls on both sides and smelling the air in the cavity.

A neighbor (two doors to LEFT) has developed the same smell in his finished basement at the same time. BOTH houses were flipped by the same corner cutting investment crew using the same materials about 3 years ago.

The house on my adjacent LEFT (in between mine and the neighbor 2 doors down) is a recently vacant property that just sold and is about to get a full gut rehab. It is pretty gross in there. I have been inside sniffing around 2-3 times since it was put on the market. It is gross and does not smell great in there but I could NOT identify the same smell.

This smell has been noticeable for just over 2 months.

Running an ozone generator continuously inside the wall cavity effectively manages the smell, to the point of having us believe it is gone. But when the ozone machine is turned off (or died) the smell is back in 24-48 hours.

We have no idea what the smell is coming from but these are the possibilities:

a) Pets in the home made a mess in the area that was not noticed and cleaned right away. We have eliminated this as a possibility with extensive floor cleaning and running the ozone machine.

b) Sewage leak. This could be it but myself and everyone else thinks this is not a sewage smell. But it stinks!

c) Dead animal. This is my best guess. I was hoping it would deteriorate on its own but I am ready to open up some walls down there. This does not explain why the neighbor 2 houses away in the opposite direction is getting the same smell. It could be a mouse. It could also be a squirrel as they probably can get somehow via a neighbor's porch roof.

I have no other guesses as to what it could be or what to do about it. The ozone machine was running continuously for weeks and has gone kaput. The smell is back. I do need to talk to my neighbor on the RIGHT and see if he is experiencing the same thing. I've had to open up these basement walls 3x in the past 2 years for various crap that the flippers did wrong and I thought I was done with it. I do have a small handheld inspection camera and am ready to drill some small holes in the cavity and look around.

Shoot me some ideas! Somebody tag Jim K.

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Dennis M.
Rental Property Investor · Erie, PA · Member since 2018 · 6k+ posts · 9k+ votes
6y

Being it’s in Philadelphia I’d say it’s probably a dead hooker stuffed in the closet stinking up the joint

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  • George W.
    Investor · NJ · Member since 2018 · 869 posts · 921 votes
    6y

    I would see if house has a main house trap. A lot of old houses had them. Traps need vents and in row houses they used to put them in the front of the house. Which is fine until someone builds a enclosed porch over the front yard. 

    next I would check the gas meter if it's in the basement and see if the pressure regulator vent is piped outside. 

    If its not either one of those I'd fo a water test on the plumbing waste. 

    The smell could be a million other things though. What does it smell like?

    3Reply
  • Nathan GesnerBusiness Member
    Moderator
    Real Estate Broker · Cody, WY · Member since 2010 · 28k+ posts · 41k+ votes
    6y

    Dead animal odor will typically go away after a couple of weeks. If it's a really damp area, it may last longer. Two months indicates something else is going on.

    Have you checked sewer ventilation? Maybe the sewer is not vented properly and gases are pushing back into the homes?

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    4Reply
  • Dennis M.
    Rental Property Investor · Erie, PA · Member since 2018 · 6k+ posts · 9k+ votes
    6y

    Being it’s in Philadelphia I’d say it’s probably a dead hooker stuffed in the closet stinking up the joint

    8Reply
  • Joe White
    Property Manager · Philadelphia, PA · Member since 2015 · 515 posts · 196 votes
    6y

    I would have to say that it's a pet smell. Concrete is permeable. Meaning, liquid passes into it. To clean it, you would need an enzyme cleaner and it must be liquid, to pass into the concrete itself.

    1Reply
  • Max T.
    OP
    Investor · Philadelphia, PA · Member since 2015 · 3k+ posts · 3k+ votes
    6y

    Thanks for the replies!

    @Dennis M.
    @Dennis M.@Nathan Gesner

    @George W.

    Dennis you win.

    Nathan - there is a sewer trap under the sidewalk in front of the house. We are not experiencing any clogs/backups. We had a new water service line run 1.5 years ago and replaced the curb trap at that time when everything was exposed. I don't think that is it.

    George - we have a curb trap out front. There is no gas meter - the house is fully electric (heat pump, etc). I think it smells like a dead animal, but my first thought was sewage. I'm leaning towards dead animal, although not certain.

    This is a mystery!

    0Reply
  • Max T.
    OP
    Investor · Philadelphia, PA · Member since 2015 · 3k+ posts · 3k+ votes
    6y
    Originally posted by @Joe White:

    I would have to say that it's a pet smell. Concrete is permeable. Meaning, liquid passes into it. To clean it, you would need an enzyme cleaner and it must be liquid, to pass into the concrete itself.

    Hey Joe!

    We used the liquid enzyme ALOT and the ozone machine in the finished basement. That was before putting the machine in the wall cavity. Doing that was the only thing that has reduced the smell, so I'm 99% sure the smell is not coming from the finished space.

    1Reply
  • Marc Winter
    Real Estate Broker · Northeast PA · Member since 2017 · 2k+ posts · 2k+ votes
    6y

    Interesting problem.  I'd try hiring a sewer service to scope/video the main, the vent stack, and if necessary all the way out to where your main meets the sewer.

    Betcha a donut there is a sewer gas leak somewhere.

    6Reply
  • Max T.
    OP
    Investor · Philadelphia, PA · Member since 2015 · 3k+ posts · 3k+ votes
    6y
    Originally posted by @Marc Winter:

    Interesting problem.  I'd try hiring a sewer service to scope/video the main, the vent stack, and if necessary all the way out to where your main meets the sewer.

    Betcha a donut there is a sewer gas leak somewhere.

    All signs seem to point to sewer, and I do love donuts....

    But why does my neighbor 2 doors down on the opposite side have the same problem?

    Too many questions, not enough answers!

    0Reply
  • Joe SplitrockPro Member
    Moderator
    Rental Property Investor · Sioux Falls, SD · Member since 2015 · 9k+ posts · 18k+ votes
    6y

    @Max T. you should not run an ozone machine for weeks. You should run it for a few hours, then open all the windows and air out the property. I really hope nobody is living in this property. Ozone will do permanent damage to your lungs in this level of concentration. It is extremely dangerous to run in an occupied space. You should have received warnings with the machine. If you want to run something continuous, use an air purifier with carbon filters. Carbon removes smell. Since the smell is coming back, it means the source is still there.

    Pets urine, sewage and dead animals all have different smells. It is sad that I know what all three smell like! If it doesn't smell like sewer gas, then dead animal is a good guess. Dead animal should go away over time. It could also be mold, which you can test for. Gas leaks have an odor too. My gas meter at my house was leaking outside and we could smell it inside. You can have the utility check for gas leaks for free.

    @Jim K. what do you think?

    2Reply
  • Anthony Wick
    Rental Property Investor · Ankeny, IA · Member since 2017 · 2k+ posts · 3k+ votes
    6y

    I just came here for the comments. And BAM! Dennis delivers again. 

    1Reply
  • Jim K.
    Handyman · Pittsburgh, PA · Member since 2018 · 5k+ posts · 13k+ votes
    6y

    Sorry, on the jobsite. I think George W nailed it, that sounds exactly like the stink of a draining house trap.

    0Reply
  • Max T.
    OP
    Investor · Philadelphia, PA · Member since 2015 · 3k+ posts · 3k+ votes
    6y
    Originally posted by @Jim K.: and @George W

    Sorry, on the jobsite. I think George W nailed it, that sounds exactly like the stink of a draining house trap.

     So I'm not sure if I have a house trap. But I know that the sewer line has a trap out front under the sidewalk. We referred to it as the "curb trap" when we had our water service line replaced 1.5 years ago. The curb trap wasn't in great shape so I had it replaced at the same time.

    But if this is the culprit then what explains my neighbor 2 doors down having the same smell?

    0Reply
  • Amy A.
    Portland, ME · Member since 2012 · 616 posts · 550 votes
    6y

    I've seen this in several houses with finished basements.  Whatever the original odor source was (dead animal, sewage, oil, water (mold)), it wicked up the paper on the back side of the sheetrock.  This doesn't happen on the painted side, which is why you don't see the stain.  You can take off the baseboard (carefully, so you can put it back if that's not the source of the odor) and cut out a piece of sheetrock to examine. 

    I had a client with a house that cost him thousands in a lawsuit from a tenant due to an oil odor making her sick.  Nobody, not even the state dept. of environmental protection, could figure out where the odor was coming from.  Eventually, they started tearing out the finished basement and found the oil on the back side of the sheetrock, wicked up from an oil spill.

    Good luck!

    2Reply
  • Jim K.
    Handyman · Pittsburgh, PA · Member since 2018 · 5k+ posts · 13k+ votes
    6y
    Originally posted by @Max T.:
    Originally posted by @Jim K.: and @George W

    Sorry, on the jobsite. I think George W nailed it, that sounds exactly like the stink of a draining house trap.

     So I'm not sure if I have a house trap. But I know that the sewer line has a trap out front under the sidewalk. We referred to it as the "curb trap" when we had our water service line replaced 1.5 years ago. The curb trap wasn't in great shape so I had it replaced at the same time.

    But if this is the culprit then what explains my neighbor 2 doors down having the same smell?

    Because your neighbor also has a crack in his house trap, and when the water drains out of it, he gets the same stink. How old is this property? If the main stack has a cleanout, you can pop it open and run a sewer scope down the line to see what's going on. If the stack is old enough not to have a cleanout, you're going to have to chop your way into the stack to do that. This sounds a lot scarier than it actually is.

    Again, as @George W mentioned, this could really be a lot of things. You're going to have to rule out the sewer issue first. Well, second. Double-check on Denny's dead hooker.

    2Reply
  • Ralph R.
    Investor · Bethel, AK · Member since 2013 · 1k+ posts · 852 votes
    6y

    @Max T. I had mice build a nest in our oven once. They built it in the insulation between the oven box and the outer panel. We didn’t know anything was wrong until my wife turned the oven on. It killed all the mice. A while later it started to smell. I hunted everywhere. Finally I took the oven apart and found the mess. A couple years later it happened a second time. But this time I knew where to look. It’s a sweet smell and doesn’t go away. The stove was an older one with a fiber insulation. I never knew how the mice found their way in there. RR

    1Reply
  • Lynnette E.
    Rental Property Investor · TN · Member since 2018 · 2k+ posts · 2k+ votes
    6y

    I have 2 suggestions. neither good.

    1.  Maybe your flipper did not store the drywall well.  It could have been left somewhere such that a dog used it as his fire hydrant for a long time.  So the drywall may have soaked up the urine smell.

    2.  How was the row home heated 100 years ago?  Was oil delivered through a vent into the basement?  If so could the smell be that the oil tank was not drained/ cleaned/ and refilled with something inert or completely removed?  It could be that the old oil tank is buried in the basement and something fell into it and died.  Or maybe the old oil spilled over the years was not cleaned and is behind the drywall/floor.

    1Reply
  • Max T.
    OP
    Investor · Philadelphia, PA · Member since 2015 · 3k+ posts · 3k+ votes
    6y
    Originally posted by @Lynnette E.:

    I have 2 suggestions. neither good.

    1.  Maybe your flipper did not store the drywall well.  It could have been left somewhere such that a dog used it as his fire hydrant for a long time.  So the drywall may have soaked up the urine smell.

    2.  How was the row home heated 100 years ago?  Was oil delivered through a vent into the basement?  If so could the smell be that the oil tank was not drained/ cleaned/ and refilled with something inert or completely removed?  It could be that the old oil tank is buried in the basement and something fell into it and died.  Or maybe the old oil spilled over the years was not cleaned and is behind the drywall/floor.

     Thanks Lynette good ideas but the house was purchased over 2 years ago and this problem just started. So any stinky drywall would have been smelling bad before now. There may have been an oil tank in the basement but it was removed many many years ago. 

    0Reply
  • Michael Ablan
    Real Estate Broker · Watertown, NY · Member since 2016 · 1k+ posts · 1k+ votes
    6y

    @Max T. -  I had an issue like this in my house once.  There wasn't proper venting in my drain plumbing.  We added it and the smell went away immediately.

    1Reply
  • Bjorn AhlbladPro Member
    Investor · Shelton, WA · Member since 2017 · 6k+ posts · 6k+ votes
    6y

    Sometimes low flow toilets and old house plumbing don't mix well and crap stays in the pipes. I would go with the advice to clean up existing lines and traps. For a long term fix you may have to reinstall toilets with larger tanks.

    0Reply
  • Sylvia B.
    Rental Property Investor · Douglas County, MO · Member since 2014 · 1k+ posts · 1k+ votes
    6y

    We had an unidentifiable smell in the old (100+ years) farm house we lived in. At about the same time we discovered a termite infestation. Once we got rid of the termites, the smell went away. Strange, but true.

    0Reply
  • Oscar Beteta
    Rental Property Investor · Blue Bell, PA · Member since 2018 · 93 posts · 12 votes
    6y

    @Max T.

    Hey Max! Any updates on the source of the smell?

    I’d be happy to troubleshoot with you one of these days! Very intriguing!

    0Reply
  • Max T.
    OP
    Investor · Philadelphia, PA · Member since 2015 · 3k+ posts · 3k+ votes
    6y

    @Oscar Beteta

    It is sewer gas. The water department found a problem at a neighbors property that is causing the smell.

    1Reply
  • Oscar Beteta
    Rental Property Investor · Blue Bell, PA · Member since 2018 · 93 posts · 12 votes
    6y

    @Max T.

    Any more detail on how that problems made it into your finished basement? Just smell traveling through cracks?

    0Reply
  • Max T.
    OP
    Investor · Philadelphia, PA · Member since 2015 · 3k+ posts · 3k+ votes
    6y

    Found it!

    At one time this home had 2 separate sewer lines - one for stormwater from the roof/outside drain, the other for wastewater from sinks/tubs/toilets. Now both of those lines have been combined into one (philly has combined wastewater system so this is normal).

    Well I decided to poke around behind the finished basement walls with a handy handheld inspection camera. I traced my sewer line along the whole basement via several access panels and outlet boxes, and I found no leak no broken pipe.

    But eventually I traced it all the way to the front of the house and found this hole (top circle) after moving a lot of loose dirt around. This hole is one of the old sewer lines, before it was combined. The bottom circle is the new pvc sewer line in good shape all the way through.

    So I plugged it up with a bucket of hydraulic cement... and presto! No more smell.

    4Reply
  • Max T.
    OP
    Investor · Philadelphia, PA · Member since 2015 · 3k+ posts · 3k+ votes
    6y

    @Max T.

    Aaaand I’m back. Yes replying to myself. So I took care of the smell but must have closed off the fuc$*!’s escape hole. Yes I have a rat. Not a mouse. Heard him scurrying around behind the ceiling drywall down there. Found a couple droppings in an access panel. I’m familiar with mice so I know this is a RAT. But I’m happy now because I have a new (Coronavirus isolation) purpose in life.

    2Reply
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