Sewer smells

Jeff Horton

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The Heart of Dixie
Got a mystery on my hands and someone probably knows the answer. I started getting a sewer smell in my house the last few days. Being a Home Inspector I can find it, right? I understand the basics of plumbing and first suspected a P trap had lost it's water seal. So I went to the bathtubs and ran water since they are least used fixtures in the house. Assuming the water had evaporated in the P trap. This happened once before so I was sure that was it.

Didn't fix it.

So I ran water in all the fixtures just to make sure the P-traps had water in them. Still smell it.

I have partial basement and 85% of the plumbing is in there. I smell it there and that may be where the smell starts and works into the house. No plumbing leaks and I use the fixtures down there regular too. But I ran water in all them to make sure they were sealed too.

That didn't work so this morning I crawled under the house. I am thinking a line might have broke in the crawl space. Nope and no leaks or smell there either. Then I Climbed on the roof to check the vents and everything looks good.

Now I am stumped! The only way I know for a smell from the septic tank to get into the house is though a drain line. Either a broken line or empty P trap and I can't find either. Anyone think of something I missing?
 
The one drain that gets forgotten alot is the floor drain in the utility room in our basement. It has a p-trap too but it's below the concrete floor.
 
Any chance the tank is either over flowing or leaking and seeping into the ground near a foundation vent? How close is the tank to the house?
 
Todd, I thought of that and that is why I went on the roof to look. If it was clogged I would expect the toilets to empty all the water out. So I am thinking that is not it.

Ken, no floor drains but that would be a good one to miss and would make total sense.

Rennie, to far from the house. Plus I would probably smell it outside.

Smell is not really strong so that is what is making it so hard to tell where it is coming from. I been spraying poly the shop this morning so my fan is going sucking air out. That should pull the smell out and maybe if it comes back and I narrow down where it is starting.
 
I don't think so. I should be able to locate that if it was. I went under the house in the crawl space thinking it might be something under there and not in the basement section or inside the house.

I am really stumped.

Just went to the shop and fan is going and I smell nothing but the faint smell of the waterproofing I am spraying. So maybe this will remove the smell and if it comes back I figure where it starts.
 
I dont know much, but Ill add my 2 cents.
Whenever barametric pressure in the atmosphere change, like during a storm, or whatever, sewer gases, and Im not sure which is heavier, the sewer gases, the air....but if theres a chance of them leaking in a tiny crack of a sewer vent, they will be most prominent when the pressure changes.
I dont think the venting outlet itself will have an odor, it may be somewhere along the line, in the walls, floor, attic?
 
OK, I think I am onto something. Someone mentioned they had seen this happen in the spring when there were high winds. I had another house that every time we had heavy rain you would smell the same thing and sometimes when it was very windy. I had forgotten about that too. That house was built on a slab so I assumed there was a problem with the plumbing since I couldn't see it.

Now I still don't know why high wind would cause this but it did start the day we had some really strong winds. And since my other house did this I think this is related to the wind. But why it would cause this I still don't understand. But it sort of lines up with what you were saying Allen.
 
do not intend to hi-jack this thread but what is the purpose of the vent pipe /
I've heard different versions for the vent pipe
 
is the pipe from the house to the septic tank running uphill ? the high winds could be pushing the sewage from the leach field to the house or a underground spring could carry the waste water to the house
 
do not intend to hi-jack this thread but what is the purpose of the vent pipe /
I've heard different versions for the vent pipe

Two purposes:

1. Vent off sewer gas

2. Most importantly, it keeps the pressure in the pipes equalized as the water flows through the pipes. Excessive positive pressure can push the waste into the fixture and excessive negative pressure can drain the siphon which would introduce sewer gas into the house.
 
To add to what Bill said, if you don't have a vent (or it is to small) when you flush the toilet and the water runs down the pipe it will create a vacuum and suck all the water coming in, out of the toilet. The vent allows air into the lines and prevents that vacuum.
 
Could the high winds be blowing past the vent pipe and applying a vacuum to it, kind of like how an airbrush works? Would vacuum applied to the vent pipe cause sewer gas to enter the house?
 
Could the high winds be blowing past the vent pipe and applying a vacuum to it, kind of like how an airbrush works? Would vacuum applied to the vent pipe cause sewer gas to enter the house?

let see, if the pipes are in the house then the sewage are in---the pipe/ I think that you figure this problem out correct--stick a drinking straw in a bottle of water and blow across the end of the straw/ the water will rise up the straw if you do this right/ do you siphon gasoline ?do not answer last question
 
Two purposes:

1. Vent off sewer gas

2. Most importantly, it keeps the pressure in the pipes equalized as the water flows through the pipes. Excessive positive pressure can push the waste into the fixture and excessive negative pressure can drain the siphon which would introduce sewer gas into the house.



will the positive pressure increase if the vent pipe get a stoppage and HOW can I unstop the vent pipe ?
 
Sounds like it's back drafting. Is the vent pipe to code above the roof? To short will cause back drafting in high winds.
 
Sounds like it's back drafting. Is the vent pipe to code above the roof? To short will cause back drafting in high winds.

No code here. Actually by law we are under the Southern Building Code but there is not enforcement outside the cities. And I don't know what code requirements are but I am going to look into that.
 
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