Sewer smell

SlamDunk

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.

Jamie Hall

dry trap somewhere? Basement floor drains are often overlooked...

SlamDunk

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

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

You may have a trap that’s not vented properly. Every now and then the trap seal is sucked out after it drains. 

Derheatmeister

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

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

mattmia2

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

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

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

  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.....
        
   

Mad Dog_2

Hydrogen Sulfide IS corrosive. Present in all DWV systems that convey raw sewage  Mad Dog 🐕 

Jon_blaney

Clothes washer!

Mad Dog_2

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

SlamDunk

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

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 🐕 🤣 

JUGHNE

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?

mattmia2

The cooking lead acid battery can smell exactly like a sewer.

Alan (California Radiant) Forbes

SlamDunk

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

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

SlamDunk

@mattmia2 I don't understand. Washer is nowhwere near a sink. I have to look up wet vent.

SlamDunk

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

Hi @SlamDunk , Could you share photos of the washer hookup? Just maybe an air admittance valve could help here.
Yours, Larry

SlamDunk

@Larry Weingarten , at the moment, I cannot. But it resembles this:

PC7060

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

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

That may very well be your problem @SlamDunk. Put a trap on that bad boy. 

Jamie Hall

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.

SlamDunk

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

Looked it up. I understand! Thank you everyone. Hopefully, that is the only problem.

mattmia2

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

SlamDunk

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

line is not trapped.    But they did give me two clean out tees.   

SlamDunk

hot_rod

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.

JUGHNE

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?

HomerJSmith

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

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

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 )

SlamDunk

Oh, the dehumidifier drains into the sump. Eventually, sump pumps it to daylight.