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Mystery Sewer Gas From Vanity in New House

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BGS

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I purchased a newly constructed home in January of this year. Shortly after moving in we started to smell sewer gas in our master bedroom and bathroom. We also smelled it alot outside the house. The contractor replaced the seals under the toilets and extended our vent stacks on top of the roof 3 feet. The smell inside the house went away however the outside smell continued. We also started to get a poof of sewer gas smell that would come up from our vanity sinks in our master bathroom. The smell would poof up when the water was continuously running for a few seconds then stop. It did it when running hot or cold water and mainly after they had sit unused for a few hours. If we let them sit unused for a few hours then turn on the water the poof of sewer gas would come up then go away. We would shut off the water and then turn it back on and no sewer gas would come up again until we let it sit for awhile again.

We spoke to our next door neighbors who moved in to their new house build by same contractor the year before and they said they also had/have a sewer gas smell as well. They only had one vent stack coming out of their house and multiple AAV values.

We called the contractor again who this time had the plumber who installed the system there also. Of course no one smelled it except us and one of the honest helpers with them. They checked the pipes on the house and they were working correctly when flushing. They took off the cap to our septic and there wasn't any smell coming from it. We even bought a sniffer device from amazon which detects Methane and it hit when the smell would poof up out of the sinks. During our discussions we found out we and our next door neighbors were on a county water line what was on the very end of the system. The contractor paid for a water test which came back good.

We asked the county to do more flushing of the system since we were on the end of the line. After they blowed us off we a few times we contacted the state regulatory agency who got them to do choline testing which results where almost 0. We started to notice the smell was in the water and tested it by filling up a cup and smelling it. They have now setup an auto flushing system on the flushing point downstream from us and we can now smell a slight hint of choline in our water which is normal to what we have smelled in the past on other municipal water systems we have had.

The smell from our vanity sinks has come back just like mentioned above. We do not smell it outside like mentioned above but its back in our sinks the same way. The only other thing we have tried was pouring bleach down both drains. I have also replaced the only AAV value that is in the house (Located in the basement bathroom) with a better quality one just to eliminate that possibility. I have also checked the drain from the hot water heater that goes out the basement floor by flushing it some.

At this point I don't know what else to try and who to hold responsible at this point the contractor or the water department or someone else. Any help or suggestions would be appreciated.
 

Jeff Handy

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Clorine, not choline.
Valve, not value.

You can have a smoke test done by a plumber, where they inject harmless smoke under pressure into your entire drain system.

It will leak out and be seen, any place that is not properly sealed.

Sometimes there are open vent connections behind the walls, for example.
Or in the attic.

Are you in an area where fracking is being done?

That can pollute the water with natural gas or other contaminants.

EDIT It was pointed out that even I misspelled chlorine as “clorine”, haha.
My bad!
 
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Jeff Handy

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You can have your water tested, to see if you have any high levels of minerals or contaminants.

Also, if the chlorine treatment from the city is not working right, you might have high bacteria levels, which can cause stinky water.

You might need to install your own chlorine treatment system at your point of water entry, and maybe sue the city (or negotiate) to pay for it.

Also, a two stage whole house water filter, with a sediment filter and a charcoal filter.
 

Mitchell-DIY-Guy

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You indicate your location as "The South".
You said "They took off the cap to our septic and there wasn't any smell coming from it."
You said "We started to notice the smell was in the water"

So, are you on a municipal sewer, or on a private septic system? Is the private septic system your own, or a community/subdivision? If private, you are on your own. If community, the collective owners need to (perhaps) pay for what isn't right, if anything...so, let's talk about this.

SEWER: If you are on a municipal sewer, the tap to the main in the street needs to be lower (of course) than the exit from your house. Raise the possibility that there's not enough slope thus not enough effluent flow; leaving effluent in your drain lines. In the northeast, midwest and other places where temps go below freezing for months out of the year, sewer mains and taps are deep below grade level, in some cases more than 5'; almost impossible not to have enough flow or slope. Here in NC, also "the south", no so much! So, some houses that sit below the street grade have, IMHO, a questionable flow. Just something to consider.

SEPTIC: The same flow as above holds true for septic. But in a private system, now you have tanks to contend with. In many modern systems there are two or three tanks along with "dosing" of chemicals. It all has to work well in harmony and there are a boatload of rules and regulations and more importantly, operational specifications on how it all works together. So if you are on a private system of any kind you need to ensure it all works the way it was designed to. There are licensed experts in each locality familiar with the requirements.

WATER: You said there was a smell in the water. Since the county or municipality is responsible for safe and healthy drinking water (presumable that which is free of methane, toxins or smells) they should pay for the necessary equipment to deal with it and if they are giving you trouble you are right in going to the state AND/OR the EPA if necessary. Here's a bit about methane in well water but the take away is how to deal with it... Methane Gas and Its Removal from Water Wells
 

BGS

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Yes mentioned that the contractor had a water test done. They tested for E.Coli and Coliform results showed Absent.
 

BGS

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You indicate your location as "The South".
You said "They took off the cap to our septic and there wasn't any smell coming from it."
You said "We started to notice the smell was in the water"

So, are you on a municipal sewer, or on a private septic system? Is the private septic system your own, or a community/subdivision? If private, you are on your own. If community, the collective owners need to (perhaps) pay for what isn't right, if anything...so, let's talk about this.

SEWER: If you are on a municipal sewer, the tap to the main in the street needs to be lower (of course) than the exit from your house. Raise the possibility that there's not enough slope thus not enough effluent flow; leaving effluent in your drain lines. In the northeast, midwest and other places where temps go below freezing for months out of the year, sewer mains and taps are deep below grade level, in some cases more than 5'; almost impossible not to have enough flow or slope. Here in NC, also "the south", no so much! So, some houses that sit below the street grade have, IMHO, a questionable flow. Just something to consider.

SEPTIC: The same flow as above holds true for septic. But in a private system, now you have tanks to contend with. In many modern systems there are two or three tanks along with "dosing" of chemicals. It all has to work well in harmony and there are a boatload of rules and regulations and more importantly, operational specifications on how it all works together. So if you are on a private system of any kind you need to ensure it all works the way it was designed to. There are licensed experts in each locality familiar with the requirements.

WATER: You said there was a smell in the water. Since the county or municipality is responsible for safe and healthy drinking water (presumable that which is free of methane, toxins or smells) they should pay for the necessary equipment to deal with it and if they are giving you trouble you are right in going to the state AND/OR the EPA if necessary. Here's a bit about methane in well water but the take away is how to deal with it... Methane Gas and Its Removal from Water Wells
We have county (Municipal) water but not Municipal sewer system. We have a private septic system. Good information we could have more than one thing going on. The water either way needs to be at the correct levels for sure but just wondering if the venting is still not the issue with the smell. Just trying to pin point if it is a venting issue with plumping or water issue or a combination of both. I don't think I mentioned that the bathroom located on the other end of the house doesn't have the smell.
 

Jeff Handy

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Smoke test will reveal any venting leaks.

It will not reveal if any vents are blocked.

It will reveal if traps are being sucked dry from poor venting.
 

Jeff Handy

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Actually, a smoke test would show if the main vent out the roof is blocked, no smoke would come out of it.
 

BGS

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Yea the plumber climbed up on the house and I flushed the toilet and air was definitely coming out. Not sure if that is the correct way to test but they said it was working. Just wonder what would cause gas coming back up and out the sink when water is continuing to run down. That is the question because I do not smell it in the water from a cup anymore it is gas coming up like before.
 

BGS

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UPDATE: We have pinpointed that the smell is coming from the cold water and not coming up from the drain as first suspected. It is only there if we use cold water and doesn't smell if we use hot water. If the vanity isn't used for a hour or so when cold water is turned on it gives the rotten egg smell for a few seconds then goes away.

Contacted county water system officials (Yes we are on a municipal system not well) and state who have done more flushing of the lines in the area. They have tested for chlorine levels and bacteria. Chlorine levels have been low and bacteria tests all came out good or not high enough to be regulated. The smell is still there so we are now back to the plumbing in the new house. The issue is concentrated on one side of the house which is also the side that has the hot water heater. I have been told everything from the hot water heater to crossed lines to my garden hose hooked up to my house could cause this.

Everyone seems baffled ....plumber, contractor, water system, and myself. Does anyone have any suggestions on what possibly could cause this issue in the cold water?
 

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