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Champion Thread Derailer
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Discussion Starter · #1 ·
Not sure if I'm posting this in the right place, but I wanted to present this question/problem to the forum here in hopes of someone being familiar enough to advise on what's happening and what might be a solution.

I live in a somewhat rural part of the county (Chatham Co.), which is serviced by municipal sewage system (Siler City approximately 3 miles away). To my understanding, this system was installed in my area of the county about 12 years ago.

Since I moved to this location in 2006, there has always been an occasional problem with horrific sewage gases emanating from a vented man-hole cover about 200 feet down the street, which, when it happens, it fills the entire area (about 5 neighboring yards/homes) with an overpowering smell of raw sewage. This problem has progressively worsened over the period of time I've been here, but I must add that it is generally worse during the winter months. It is now so bad at times one simply cannot stand being outdoors. Sometimes the smell even enters my house, and all of the neighboring homes as well.

I have, over the years, called the city many times about this problem, and nothing has yet to be figured out as to what is happening, much less what is a remedy. I am told (by the city workers) that before I moved here, the man-hole cover directly in front of my house was previously a vented cover too, but was replaced.

A couple of weeks ago the city came out and replaced the vented man-hole cover 200 feet down the street with a solid cover. Since then the smell in the house has gotten so bad (usually during the overnight hours) that it renders the house unlivable. I certainly can't sleep with this being so bad.

Anyway, other than what I already said, here is what I do know about the system: the man-hole cover 200 feet down the street is the beginning of the 8 inch gravity sewer system. There are about 6 houses beyond this point that feed into the gravity system (at the man-hole 200 feet away) via a 2 inch line, and pumps (and a pit) at each home.

Also, there have been 2 blower/smoke tests done where there was no smoke, or smell of smoke (kind of smells like baby oil), found in any of the houses, including mine, on either occasion. It was certainly coming out very well of the vent stacks on each house; but nothing inside, in the attic, or under the house. Regardless, I have pulled the toilet and replaced the wax ring, just in case it was bad. This was inexpensive and easy to do, thus is why I tried it, but it did nothing to change the problem, which is now happening every night typically anywhere from 11pm to 5am. I can't sleep.

I am really at wit's end, and don't know what to do, or even who I should call that would have any authority, or capability, to find and fix the problem.

Any advise would be GREATLY appreciated. Thanks!
 

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Thom
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If the sewer gas is entering directly into your home (not just ambient gas outside entering through windows, doors, or house leaks, you have a vent/seal problem.

Maybe you have a dry trap, maybe a leaking vent. If your house is reasonably tight and you run an exhaust fan you could be drawing in sewer gas to make up for the air exhausted out.

Try doing the opposite, pressurize your house. See if that changes things. If the smell is in the ambient air outside, you cannot fix the problem without fixing the sewer system.
 

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Champion Thread Derailer
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Discussion Starter · #4 ·
If the sewer gas is entering directly into your home (not just ambient gas outside entering through windows, doors, or house leaks, you have a vent/seal problem.

Maybe you have a dry trap, maybe a leaking vent. If your house is reasonably tight and you run an exhaust fan you could be drawing in sewer gas to make up for the air exhausted out.

Try doing the opposite, pressurize your house. See if that changes things. If the smell is in the ambient air outside, you cannot fix the problem without fixing the sewer system.
Yes, I thought the same thing, but the blower/smoke test did not indicate any leaks, in any of the houses in question. They all, however, simultaneously exhibit the very strong smell of sewer gases (4 houses total). Previously, when the man-hole cover in question was the vented variety, the smell inside would always coincide with the smell outside. One didn't happen without the other. Now that the man-hole cover is solid, things are different as there is more of the smell inside the homes than previous.

Further, the sewer gases, particularly in a gravity fed system, should be going up the vent stacks and out into the air above the roofs. But it is not (at least not completely). I suspect the over pressurization that is occurring (and it must be if the blower/smoke test isn't showing any leaks with the pressures its putting on the venting systems in the houses) has something to do with the pumps/pits from the 6 houses that feed via a 2 inch line into the gravity system. The city, however, has not done anything, to my knowledge, to eliminate the possibility of one of these 2 inch lines of pumped sewage going septic before it gets to the man-hole 200 feet down the street.
 

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Thom
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Jeff, the smell from a neighbors line would not enter your house unless there were a problem in your vent system.

It is not unusual for restaurants especially to draw sewer gas through a dry trap, even a wet trap. their exhaust fans at the hood remove air rapidly and, if there is not enough make-up air that partial vacume will be made up somewhere. If you walk into a restaurant and the door is hard to open followed by an inrush of air, that is the problem. Anyway, that suck can pull air through a trap and into the building leaving behind a stink. Of course the first places to look are for dry floor drain traps (like an unused shower) then sinks, unused washing machine hook-ups, etc. Sometimes people remove a fixture without properly plugging the sewer, sometimes they remove a clean-out plug and don't replace it or don't properly replace it. Sometimes the leak is inside a wall where it would take a long time for the smoke to become visible in the house.

Check to see if the ejector pump is fully sealed. It doesn't take much of a leak to allow pressurized sewer gas to leave behind a big stink.

If you get real desperate for a solution, Plug your sewer where it leaves the house with a donkey dick (air type expansion plug) then plug all your roof vents. One at a time, remove the vent plug and see if you can pressurize (very low pressure) that vent line. If everything is sealed you will blow bubbles through a trap which will create some back pressure. You should need to do this only on a single vent as long as all of the vents are plugged.
 

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Champion Thread Derailer
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Discussion Starter · #6 ·
Thank you for the replies, Thom.

I completely understand what you are saying. But, one of the things that simply isn't making sense to me is why would the same problem be affecting all the houses closest to the man-hole in question? The smoke did not show up in any of the homes, and the smoke ran for about 30 minutes each time, perhaps a little longer.

This is, admittedly, one area I am not very familiar with, but I do, however, believe it has something to do with the pumps down the street (each about a 1/2 mile away). Otherwise, it doesn't make sense to me that a gravity fed sewer system would be building up pressures on occasion like is happening. In my mind, what's worse is the folks at the city are stumped on this one, and I'm left wondering who to call next.

Thanks again for the help!
 

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Champion Thread Derailer
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Discussion Starter · #7 · (Edited)
Oh, I forgot to mention that since I went out last night and cracked open the man-hole cover (the new solid one) the problem went away. When I put it back into place early this morning, the smell came back in the house during the early morning hours. At this point, I took my flashlight and shined it down into the bathroom sink where I could see the water in the trap, and there were bubbles all around the edges of the pipe.

I have just went out and cracked open the lid again (I pried it up and put 3 small sticks of #5 rebar under it), but will put it back into place first thing in the morning, then I am calling the city to ask if they will put the vented lid back on. I'd rather have the smell permeating the neighborhood, for the time being, as opposed to the house, and the neighbors feel the same way. I just hope this can get figured out.
 

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A couple of questions come to mind.

1. Why did the manholes have vented lids in the beginning?

2. Why were the vented lids changed to unvented lids?

3. When a presssurized line is pumping, where is the displaced gas supposed to go?

4. What time of year was the smoke test done?

5. What is your location?

I'm in central Iowa and we have had some below zero weather for the last few weeks, along with some snow. I got an email from a lady this morning asking about some new gurgling sound in her shower when a toilet is flushed. I responded by asking her if she had noticed anything outdoors which could have contributed to the problem. She couldn't figure it out, so I told her that her vent line was probably plugged and it wasn't anything to worry about and would probably be fine as soon as we get above freezing again (thursday). I have noticed a few vents just from the street with caps of snow on top of them.
 

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Champion Thread Derailer
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Discussion Starter · #9 ·
A couple of questions come to mind.

1. Why did the manholes have vented lids in the beginning?
I asked the same question to the city workers, including the public works director, all to no avail. No one had an answer, at all.

2. Why were the vented lids changed to unvented lids?
I am assuming the one in my front yard was changed due to someone complaining about the smell. Of course, this was prior to my arrival here in 2006. The lid down the street (at the beginning of the gravity fed system) was change about a month ago to alleviate the complaint regarding the over-powering sewage smell coming from that location.

3. When a presssurized line is pumping, where is the displaced gas supposed to go?
I would guess out the roof vents of the houses in close enough proximity?

4. What time of year was the smoke test done?
The first was done about 3 weeks ago, and the last one was about 2 weeks ago.

5. What is your location?
Central North Carolina, about 30 miles south of Greensboro and 45 miles west of Raleigh.

I'm in central Iowa and we have had some below zero weather for the last few weeks, along with some snow. I got an email from a lady this morning asking about some new gurgling sound in her shower when a toilet is flushed. I responded by asking her if she had noticed anything outdoors which could have contributed to the problem. She couldn't figure it out, so I told her that her vent line was probably plugged and it wasn't anything to worry about and would probably be fine as soon as we get above freezing again (thursday). I have noticed a few vents just from the street with caps of snow on top of them.
Yes, this is an interesting phenomena, but I don't believe it has anything to do with the problem my neighbor and I are experiencing. This is merely my opinion based upon the smoke pouring out all the vents penetrated the rooftops on each house during the smoke test, as well as this intermittent problem also occurs at any point during the year. It is, however, more prevalent during the winter months.

Thanks for the help!
 

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Thom
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Jeff, you said you noticed bubbles coming through the water in the trap. That shouldn't happen though it could if a studor-vent was used or the roof vent is plugged or improperly installed.

Those bubbles are a likely candidate for the sewer gas and the smell.
 

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Champion Thread Derailer
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Discussion Starter · #11 ·
Jeff, you said you noticed bubbles coming through the water in the trap. That shouldn't happen though it could if a studor-vent was used or the roof vent is plugged or improperly installed.

Those bubbles are a likely candidate for the sewer gas and the smell.
Yes indeed, but I have no Studor vents in the house, and I have ran a 1-inch clean-out snake down the vent on the roof, as well as ran the water hose up on the roof and let the water run in the pipe for about an hour. I never saw any issues.

But, like I've previously said, all the 4 houses in close proximity to the man-hole in question, have the very same issues happening, including bubbling in some trap. Not to mention, the smoke test didn't show any signs of leaks, but there were bubbles in some traps and the toilets were all bubbling while the test ran for a little over 30 minutes each time.

Do you have any idea why this smell could be happening at some times and not others. I am guessing the system can only be pressurized by the pumps feeding the sewage from the pits belonging to the 6 homes down the street a ways. The closest home//pit/pump is about a 1/2 mile away and the furthest is a 1/4 mile, or so, beyond it.

Also, I was wondering if you had any ideas why the smell gets so bad during the nighttime or early morning hours? This has happened every night over the past two weeks. It seems to me that the sewage smell would be more prevalent during the hours people are typically awake (i.e., more apt to be using the system). I am wondering if any of the neighbors down the street, who have various livestock (cows, bulls, goats, chickens, and I don't know what else), are having something tying to the sewage system? I really don't know what is going on, but have been hopeful the city water and sewage department could get the problem figured out.

Lastly, this problem isn't happening 24/7, 365 days a year; it generally happens 3 to maybe 6 times a year (however, it's been much worse this year), and typically worse in the wintertime. If it were a vent problem in the houses, shouldn't I be smelling these sewage gases more often?

Anyway, as I've said before, I really do appreciate you taking the time to offer input.
 

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I was thinking the smoke test was done when the weather was warm and the vents were open and they had maybe frozen shut since then.

Could atmospheric pressure have something to do with this? Does it get smelly when it is overcast and no wind and maybe drizzly, or does it happen when it is sunny and windy and clear weather?

Is the municipality willing to put the vented lids back on and do a sort of practical test?

I guess we don't really have to understand what is happening if a solution can be found.
 

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Champion Thread Derailer
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Discussion Starter · #13 ·
I was thinking the smoke test was done when the weather was warm and the vents were open and they had maybe frozen shut since then.
What is odd to me is the fact that the city has never performed a smoke test prior to the recent ones. In fact, I never knew such a thing existed.

Could atmospheric pressure have something to do with this? Does it get smelly when it is overcast and no wind and maybe drizzly, or does it happen when it is sunny and windy and clear weather?
I can't really attribute the occurrence to any specific thing. Sometimes it's sunny, sometimes not; the only thing I have noticed is it tends to happen more frequently during winter months, sometimes the temperature is really low, sometimes it is not.

Is the municipality willing to put the vented lids back on and do a sort of practical test?
I have asked about 4 days ago, and have had no response as of yet. We have, however, had a lot of snow and ice recently and perhaps this has something to do with the lack of a response as of yet.

I guess we don't really have to understand what is happening if a solution can be found.
True enough. My concern revolves around a remedy more so than a general understanding of the physics involved; but I have been hopeful of a better understanding of what's actually going on could help lead to me asking better questions that might lead to a solution, maybe. At this point, I am learning a few things about the issues going on, but I am still quite unfamiliar with much of the particulars.

One example would be: I would think that a vent problem in each of the houses would be obvious more than just a few times a year. It seems to me the sewer gases in the system would be there to escape into the houses via a leak most every day of the year. But I simply don't know for sure. To learn some of the answers to many of these issues is precisely what I was hopeful of better understanding by posing the problem on this forum. And I must add that I greatly appreciate all the help given thus far, including yours!
 

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I have installed quite a few septic systems in rural areas that are not on town sewers. Many use a pump chamber and pump to get the effluent to the septic bed. The pipe from the pump chamber goes to a distribution box which divides up the effluent and sends it down each line in the bed. The man hole you speak of is similar to our distribution boxes except it only sends the effluent out the 8 inch pipe. Is it possible that when the situation happens that several of the homes on pumps as well as the gravity ones are all sending effluent to the chamber at the same time. Would this fill the man hole up to the point that it would be so full that it would have no choice but to pull air down the lines of the gravity feed homes. This wouldn't happen under normal circumstances as long as everyone wasn't using their system at the same time. This would explain why it would pass the smoke test, and why it wouldn't do it with the vented cover on the man hole. Maybe it is requiring more air than can be supplied by your main vent stack and is drawing the water out of your traps to get more air. If the smell is inside the house it must be sucking the traps dry. This might explain why it happens in the evening probably when everyone is doing laundry, having showers, dishes ect. Maybe the manhole is undersized for the effluent going into it. Do you notice the smell from a certain fixture or perhaps a floor drain for a furnace or something. If you pour water down all the traps does the smell stop temporarily. Very strange problem. Let us know what happens and will keep an eye on your problem. Good luck.
 

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Thom
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Bubbles in a trap is a clue. That can only happen with pressure differential. The sewer is pressurized more than your house.

Maybe the sewer, maybe the house.

You can test the house with a manometer. It will measure the difference between indoor pressure and outdoor pressure. You could test the sewer the same way. That will at least tell you if the problem is the house or the sewer. Either the sewer is being pressurized above ambient (outdoor) or your house is pressurized below ambient.

If the house is pretty tight there is a chance it's the house. When anything is removing air from the house it must be replaced from somewhere if not through leaks, then through the sewer and traps.

Really, low indoor air pressure is not very unusual. Any vented gas appliance without supplied make-up air can cause it. Any exhaust fan, a fireplace, or a clothes dryer vent. If there is a decent breeze/wind an open window on the down-wind side of the house can be the culprit. If you have a mechanically vented crawl space (radon) and the crawl space vents are covered....

If the plumbing system in your home is properly vented it seems to me the more likely culprit is low indoor air pressure.
 

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I was building a pair of townhomes next to another pair and it was in November. That is when I noticed a terrible smell around the townhome closest to the new construction. I had never smelled this before or had it reported to me. They were energy star and very tight.

The smell seemed to go right down into the hole for the basement next door, so I asked the guys forming up if one of them had shat his pants or forgot to brush his teeth or something.

It was horrendous.

I went into the townhome closest to the smell and pulled the toilet and replaced the wax ring.

I talked to a plumber friend and he recommended extending the vent pipe up, so I put a coupler on the 3" line and brought it up above the ridge by about 3'.

That seemed to take care of the problem.

I haven't had any reports of a nasty smell there since, but then again that forming crew hasn't been back either.

Sometimes someone will ask why the pipe on the one side of the building is higher than the other. I guess you could call it a conversation piece.
 

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Personally I would agree with the low air pressure In the home theory. Along with that my guess is the sewer in the force main is going septic being 1/2 mile long so I would say that is why the smell is so bad.
Another culprit maybe that the direction of the force main entering the manhole is creating weird airflow a possibly a Venturi type effect as it enters the 8"
I know on some of the projects I've been involved with there have been plans for a chemical feed station to inject a chemical to knock the hydrogen sulfide down. My guess is that if the odor is that bad. It won't be long before the manholes will be replaced as the hydrogen sulfide will eat the concrete.
 

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Champion Thread Derailer
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Discussion Starter · #18 ·
I have installed quite a few septic systems in rural areas that are not on town sewers. Many use a pump chamber and pump to get the effluent to the septic bed. The pipe from the pump chamber goes to a distribution box which divides up the effluent and sends it down each line in the bed. The man hole you speak of is similar to our distribution boxes except it only sends the effluent out the 8 inch pipe. Is it possible that when the situation happens that several of the homes on pumps as well as the gravity ones are all sending effluent to the chamber at the same time.
There are only the 2-two-inch lines (the pumped sewage lines) feeding into the man-hole, which is about 9 foot deep and 2 feet in diameter.

Would this fill the man hole up to the point that it would be so full that it would have no choice but to pull air down the lines of the gravity feed homes. This wouldn't happen under normal circumstances as long as everyone wasn't using their system at the same time. This would explain why it would pass the smoke test, and why it wouldn't do it with the vented cover on the man hole. Maybe it is requiring more air than can be supplied by your main vent stack and is drawing the water out of your traps to get more air. If the smell is inside the house it must be sucking the traps dry.
Very interesting analysis. Thank you for pointing that out!

This might explain why it happens in the evening probably when everyone is doing laundry, having showers, dishes ect. Maybe the manhole is undersized for the effluent going into it.
I personally don't have an answer to some of the points you've brought up, like the inadequately sized man-hole. As noted above, it is, however, quite a large man-hole, but then again, I haven't a clue with how it compares to "proper size," or rather, what it should be.

Do you notice the smell from a certain fixture or perhaps a floor drain for a furnace or something.
No, I haven't been able to associate it with a specific fixture, or occurrence.

If you pour water down all the traps does the smell stop temporarily.
I do pour water into the traps, but to no avail.

[quote Very strange problem. Let us know what happens and will keep an eye on your problem. Good luck.[/QUOTE]

Thanks for the input, as you've certainly given some things to ponder, or ask the city.
 

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Champion Thread Derailer
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Discussion Starter · #19 ·
Bubbles in a trap is a clue. That can only happen with pressure differential. The sewer is pressurized more than your house.

Maybe the sewer, maybe the house.

You can test the house with a manometer. It will measure the difference between indoor pressure and outdoor pressure. You could test the sewer the same way. That will at least tell you if the problem is the house or the sewer. Either the sewer is being pressurized above ambient (outdoor) or your house is pressurized below ambient.

If the house is pretty tight there is a chance it's the house. When anything is removing air from the house it must be replaced from somewhere if not through leaks, then through the sewer and traps.

Really, low indoor air pressure is not very unusual. Any vented gas appliance without supplied make-up air can cause it. Any exhaust fan, a fireplace, or a clothes dryer vent. If there is a decent breeze/wind an open window on the down-wind side of the house can be the culprit. If you have a mechanically vented crawl space (radon) and the crawl space vents are covered....

If the plumbing system in your home is properly vented it seems to me the more likely culprit is low indoor air pressure.
Here's the rub, Thom (at least in my mind). The house was built in the mid-1950's, and I have no exhaust fans in the kitchen or bathroom, or a fireplace. The only thing I do have is a dryer, and I have not been able to associate the smell with the use of the dryer, as the problem occurs mostly when the dryer isn't running.

But, once again, whatever the root of the problem, it is occurring simultaneously with the other houses in close proximity.

I must add, this is driving me up the wall, not to mention I cannot stand the odor.
 

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Champion Thread Derailer
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Discussion Starter · #20 ·
I was building a pair of townhomes next to another pair and it was in November. That is when I noticed a terrible smell around the townhome closest to the new construction. I had never smelled this before or had it reported to me. They were energy star and very tight.

The smell seemed to go right down into the hole for the basement next door, so I asked the guys forming up if one of them had shat his pants or forgot to brush his teeth or something.

It was horrendous.

I went into the townhome closest to the smell and pulled the toilet and replaced the wax ring.

I talked to a plumber friend and he recommended extending the vent pipe up, so I put a coupler on the 3" line and brought it up above the ridge by about 3'.

That seemed to take care of the problem.

I haven't had any reports of a nasty smell there since, but then again that forming crew hasn't been back either.

Sometimes someone will ask why the pipe on the one side of the building is higher than the other. I guess you could call it a conversation piece.
I have already replaced the wax ring, but I will try extending the vent pipe (I wouldn't think it can hurt anything), as it is now only about a foot above the roof surface.

Thanks.
 
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