I have an interesting problem here and thought I would get some opinions from some this board.

Here is some contextual information:

College Station house built in 1974.
This bathroom was added on several years ago.
I bought this house 2.5 years ago from a builder who completed a significant remodel of the place - new HVAC, electrical, PEX, etc.

The master bathroom is a a "wing" off the back of the house - it is three sides exterior walls. Sloped ceiling, so no attic space. The shower is at the end, then the toilet is between it and the vanity.

Over the past few weeks, I've been getting this sporadic smell of sewer gas. Sometime, it's faint, other times it's been eye watering bad. I have found the severe wave is generally in the middle of the day at it's hottest point.

There are 3 jacks on the roof for this bathroom. One for the two sinks, one for the shower, and one for the toilet. All have 4 ways on them to prevent the squirrels from chewing on the lead.

I had a plumber come out, run smoke through the system twice. Tore out some of the wall behind the toilet (remember, this is between the shower at the end of the room and 2 sink vanity). We even tore out some of the cabinet behind the sink closest to the toilet. The first time time, the plumber saw smoke coming from the sink plumbing, but then didn't see it all.

They came back a second time with 2 other guys and ran tests again. They said the smoke cleared up as soon as they took the 4 ways off the jacks. OK, so $1400 later, that was the determination. They put some material around the jack to help the 4 ways sit more snugly around the jack.

That was OK for a couple of day but the issue has resurfaced, although not with the same intensity. It is for sure back, though. I took the 4 ways off, and it did not help.

I smell the odor (whenever it presents itself) close to the toilet and shower. P traps in the shower and sinks are OK according to the plumber. I even "cleaned" the pipes with baking soda and vinegar. It did not help.

Now I have to call the plumber back. My opinion is it is a connection within the vent pipe system. I would need to tear into more of the wall to find which one.

Sorry for the long post. I would appreciate any ideas.

Thank in advance.

Ugh….feel for you.
We had this issue to a lesser extent. Our issue was that the HVAC blower had a floor drain under it. The floor drain had a clean out port that bypassed the p-trap and the bypass was allowing sewer gas to be sucked up by the blower and spread around that wing of the house. It was very intermittent though. Might smell it for 2-3 days and then nothing for a few weeks.

Our house was built in the 50's and we asked the previous owners about the smell and their response was that it was an old house that had "seasonal smells". Bull ***** We put an expansion plug in that bypass and it stopped immediately.

We initially thought it was a bathroom issue also though. I reseated the toilet, checked the ptrap in the shower, etc…. Had a plumber come out who looked all around the bathroom. No one ever checked the HVAC system.

It doesn't sound like this is your issue, but it might be worth thinking about just to cross it off the list.

Good luck.

We don't have an AC unit close to this bathroom, so I'm not sure that would be it. Good thought worth asking about, though.

I thought about the toilet. It is a crappy (no pun intended) builder grade Vortens. They took it off to access the wall and put a new ring on it when they put it back. I have wondered if I need to change out the toilet. I didn't know if there was an internal malfunction that would allow gas to seep out without any water leaking.

Thanks, guys. Keep the ideas coming!

ETA - had both my AC units serviced on the same day as the first plumber's trip. No indications of any clogs.

Did the plumbers that were there have a sniffer like this ?


https://www.amazon.com/Robinair-TIF8800X-Combustible-Gas-Detector/dp/B005E2MRVY/ref=mp_s_a_1_2?dib=eyJ2IjoiMSJ9.fiho-hS0TVBuqfod-JmL_xb_4bXeBPyxFE71u88uXyip3QxrTmtYvVXY8B718IQSebSh-89vg2jZDlm2-vbhlL5VxwLlscf7SGXgbIMkWM228ybr9txHzzhO2U11Rg-E5BN0BstujSA2Y4hOuCCgldzCUYofniVXf6Vvf0-yAUZnI-TrLFgytwY5BqBvG21eQ9ivVf2Jg8cljrlnNAPmhw.EWOc76pBfn6ezaw5N71Q3HUFwppR3jWLE44PobOs1HQ&dib_tag=se&keywords=tif+8800+gas+detector&qid=1716830358&sr=8-2#aw-udpv3-customer-reviews_feature_div

I did not see them with that. Would it detect sewer gas?

How old are your water heaters? If they are old, could be that the anode rod has deteriorated and that can cause a rotten egg smell in your water.

Smelling it the most when the day is at its hottest? What would cause this to occur?

I'm thinking it is a shower pan issue.

Fair question. Water heater is a 3 year old external gas tankless. It's located on a wall not shared with the bathroom.

Shower was redone 3 years ago. I suppose it's possible. I'll do a shower pan test. Thanks.

Was it done right?

jt2hunt said:

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Was it done right?

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It was done before I bought the house so I'm not sure.

OK, so it rained yesterday and the temps are milder. Smell is barely there. On Sunday evening, after a hot day, it was unbearable.

Yes it will

Are you 100% sure an ac drain is not plumbed into any of that bathroom plumbing ?

JP76 said:

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Are you 100% sure an ac drain is not plumbed into any of that bathroom plumbing ?

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I just called an AC guy to come and check those drains. I'm also going to tape over my shower drain to make sure that's not a source.

Thanks.

This won't stop the smell due to it being a shower pan. You could put a test ball in the shower drain and if you didn't smell it then you definitely know it was some type of sewer smell coming from below the test ball. But taping the drain out won't stop the smell from coming up through the shower floor.

Gotcha. Good to know. Thanks.

Not the AC. Just has it checked.

Smell is coming from behind the wall where the vanity is. When I open the doors to the cabinets under the sink, that's the most potent odor.

Can you post a picture of the plumbing under that vanity ?

I had something similar and plumber found a cracked vent pipe behind the wall where the refrigerator was. Actuality I think the pipe separated from a fitting from house shifting over 40+ years. Reconnected/fixed the pipe and never smelled it again.

jt2hunt said:

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Smelling it the most when the day is at its hottest? What would cause this to occur?

I'm thinking it is a shower pan issue.

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not an expert but here is my 2 cents:

during the heat of the day the attic is the hottest so hot air needs to escape, thus you have roof vents in the form of turbines or soffits or whatever. the hot air trying to escape also pushes down into the house wherever air will flow. makes me think that the issue for original poster is somewhere in the attic or between the walls

JP76 said:

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Can you post a picture of the plumbing under that vanity ?

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I'm going to cut into that back wall next week.

I also think the source is between the vanity and exterior wall based on the intensity of the smell inside the vanity when I open the doors. I've taped up the holes and has helped some, but it's still there, especially in the heat of the day in the late afternoon and early evening.

KDubAg said:

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I had something similar and plumber found a cracked vent pipe behind the wall where the refrigerator was. Actuality I think the pipe separated from a fitting from house shifting over 40+ years. Reconnected/fixed the pipe and never smelled it again.

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My 1974 built house does move around and it's rained a LOT this spring so that is a possibility.

I'd rip out the vanity and Sheetrock and see what's in the wall.

Consider getting a decent borescope before you rip it out and drill a hole in the back of the vanity to inspect inside the wall cavities. A borescope is nice to have and I use one more than I would have expected now that I have it.

BenTheGoodAg said:

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Consider getting a decent borescope before you rip it out and drill a hole in the back of the vanity to inspect inside the wall cavities. A borescope is nice to have and I use one more than I would have expected now that I have it.

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Good idea.

If he dislikes the vanity then get the crowbar.

I have a septic system, and have the opposite problem (in the same location). It only smells in the winter when it's really cold. Nobody has been able to figure it out so far

dubi said:

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BenTheGoodAg said:

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Consider getting a decent borescope before you rip it out and drill a hole in the back of the vanity to inspect inside the wall cavities. A borescope is nice to have and I use one more than I would have expected now that I have it.

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Good idea.

If he dislikes the vanity then get the crowbar.

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I'm OK enough with the vanity to not blow it apart. lol. I do have plans to cut more holes in the back under the sink, though. The camera idea is a good one.

Are you on septic or public sewer ?

Counterpoint said:

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I have a septic system, and have the opposite problem (in the same location). It only smells in the winter when it's really cold. Nobody has been able to figure it out so far

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Cold temps pipes contract
Smoke test in winter would likely reveal a crack

JP76 said:

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Are you on septic or public sewer ?

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Public.

PM inbound.

I just put our borescope on to charge and you are welcome to borrow it.

Got the PM. I'll reach out soon to borrow it. I have some travel this week.

Thank you!