# Intermittent Sewer smell in basement



## soparklion11 (Oct 29, 2016)

The house is a ~50 yrs old 2 story home with an unfinished basement.  Public Sanitary Sewer line to street in front of the house.  The problem is an intermittent sewer smell in the basement, most prevalent in the front of the house, near where the drain pipe from a 2nd floor shower penetrates the concrete slab floor and presumably joins the main that runs to the street.  When the smell is present, it can be overwhelming.  I don't recognize that it changes with any weather issue.

There are no obvious other signs - there is no water staining in the basement, specifically near where the drain pipe penetrates; the basement sink drains well; there has never been sewage water backing up into the basement floor drain.  The floor drain is 15 ft from the area with the worst smell and there is no smell there.

How should I go about addressing this?  I was thinking of getting a sewer line cleanout and a video of the inside of the pipe.  Is it worthwhile to examine the stack?  I don't think that it is the stack, since the sinks and toilets all drain well.


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## Snoonyb (Oct 29, 2016)

That area may also be an air circulation dead zone, where things naturally migrate too.

Today, drain lines, like floor drains must be "water primed", IE. kept wet, which prevents sewer gasses from migrating beyond the trap. 

However, assuming there is no trap, remove the grate and plug the drain (a rubber ball will work).

Make sure there is water in the sink trap.

If the odor persists, apply a urethane caulk where the shower drain penetrates the slab, making sure you bridge between the ABS/PVC and the slab, SIKAFLEX const. adhesive, carried by home desperado, is such a product.

Don't fool with the self leveling, that crap takes forever to firm up.


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## Mastercarpenty (Oct 30, 2016)

It could also be a leaking plumbing vent pipe or connection. "Sniffing" it out when the odor is barely present will usually take you right to the problem or at least to the area where it's at. If you locate the area but can't gain direct access use tubing or stacked straws to sniff through. Not the most pleasant method but it's cheap and effective. "Dead air" anywhere in a home isn't good so I'd also consider some added ventilation there too.
Phil


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## soparklion11 (Oct 30, 2016)

Thanks Phil and Snoony.  

I'll work on sniffing it out... I hadn't thought of the area in question being a dead zone, since it is at the base of the stairs and I think that just opening the door to the stairwell would generate some air movement there.

I considered sealing, but what is the likelihood that there is a leak on the other side of the wall that is generating the sewer smell?  The water trap is full.


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## Snoonyb (Oct 30, 2016)

At this point, everything is possible and it's a process of elimination.

Air movement can also be generated by changes in temperature and humidity, and without consistent disturbance stagnation will occur.


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## frodo (Oct 30, 2016)

is the p trap for the floor drain kept full of water ? 

one way to find out if it is the floor drain or not,  temp, plug the drain 
does the smelll stop ?  after it is plugged ?


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## nealtw (Oct 31, 2016)

You have checked for Nat gas leaks or poor draft at the furnace exhaust.


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