Hi... I'm new here. I know that similar questions like this have been posed here before, but I'm still confused about my situation...

We just bought a house a few months ago. It's a modular. Ever since we bought the place, there has been a sewage odor coming from the master bath vanity cabinet. There is a septic system. It was inspected (as per new property/home inspection guidelines for our state) and determined to be functioning properly, with no damage. We also had it pumped out right before we moved in. When we traced the source of the odor, it appeared to be coming from an open pipe under the vanity. The guest bath has the same type of pipe layout, and there is a capped pipe in the same position in the pipe work there as the open pipe in the master bath. There is no odor at all in the guest bath. On some days, there is no odor from that open pipe in the master bath. On most days, there is a faint odor. On very hot days, there is a very strong odor - and this odor comes from the open pipe, as well as from outside. There are no vents to the roof. The obvious solution would be to cap that open pipe until we can get the pipework done to vent it through the roof properly. However - sometimes the odor comes from the floor under the vanity. Whenever we have detected the odor, it's been fairly easy to trace to a specific point, as far as surface goes. There is also a mysterious wet spot that shows up on the inside of the vanity cabinet periodically, between the doors. There is no leak in the cabinet itself, and we pulled up the floor of the cabinet to check under it and behind the toe kick - and it's dry as a bone under there. No signs of leakage whatsoever, and no pipes at all under that mystery spot. Any ideas? We suspect a cracked or broken sewage pipe somewhere is responsible for the odor, and we're having that checked out, but if there could be any other possible cause(s) it would be helpful to check those out too... What are we missing? Oh - we tried snaking all the drains in the house, tried the bleach and boiling water. The snake found no clogs anywhere - all the lines were clear, including the main line. And the bleach helped for two days. But the odor came back. We're so confused...

Thanks for any help!

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Originally Posted by RavenKnighte

Hi... I'm new here. I know that similar questions like this have been posed here before, but I'm still confused about my situation...

We just bought a house a few months ago. It's a modular. Ever since we bought the place, there has been a sewage odor coming from the master bath vanity cabinet. There is a septic system. It was inspected (as per new property/home inspection guidelines for our state) and determined to be functioning properly, with no damage. We also had it pumped out right before we moved in. When we traced the source of the odor, it appeared to be coming from an open pipe under the vanity. The guest bath has the same type of pipe layout, and there is a capped pipe in the same position in the pipe work there as the open pipe in the master bath. There is no odor at all in the guest bath. On some days, there is no odor from that open pipe in the master bath. On most days, there is a faint odor. On very hot days, there is a very strong odor - and this odor comes from the open pipe, as well as from outside. There are no vents to the roof. The obvious solution would be to cap that open pipe until we can get the pipework done to vent it through the roof properly. However - sometimes the odor comes from the floor under the vanity. Whenever we have detected the odor, it's been fairly easy to trace to a specific point, as far as surface goes. There is also a mysterious wet spot that shows up on the inside of the vanity cabinet periodically, between the doors. There is no leak in the cabinet itself, and we pulled up the floor of the cabinet to check under it and behind the toe kick - and it's dry as a bone under there. No signs of leakage whatsoever, and no pipes at all under that mystery spot. Any ideas? We suspect a cracked or broken sewage pipe somewhere is responsible for the odor, and we're having that checked out, but if there could be any other possible cause(s) it would be helpful to check those out too... What are we missing? Oh - we tried snaking all the drains in the house, tried the bleach and boiling water. The snake found no clogs anywhere - all the lines were clear, including the main line. And the bleach helped for two days. But the odor came back. We're so confused...

Thanks for any help!

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Hey Raven,

Thanks for picking up on the answer to the code questions in the State of Hawaii. It was very informative.
Now, open line under your vanity? What's it's purpose? And why is the other line capped off? It really sounds to me like both pipes are vents that weren't run out the roof. If that's the case you have one open to the sewer allowing sewer gas to escape and the other capped off so you have no vent at all and a "S" trap that has been outlawed for years. If that's the case, and if you have no vent coming out the roof then whoever installed your modular home neglected to run vents on your fixtures and left you with a open line to the septic tank that lets sewer gas into your home. This is a dangerous situation and shoulr be remedied at once. Sewer gas is hazardous to your familys health and the methane content's explosive. DO NOT ALLOW THIS TO CONTINUE! Get a licensed plumber out there to check the systen and advise you as to the repair. Ifyou just purchased your home it should still be under warranty and the contractor/ installer should be lible for all and any repairs. Please keep me in the loop and keep me informed. Tom

Hey, Tom...
No prob. Like I said, I was born and raised in Hawaii and the codes change there every 10 years or whenever new developments in safety issues happen (I assume it is the same all over).

I don't know what the purpose is of the open line under the vanity, although regarding that, we suspected as you do - it was supposed to be a vent that was supposed to have been run through the roof that was never completed. It turns out that this is exactly the problem. It wasn't a cracked pipe or anything like that, as we had also suspected.

As far as a warranty goes - this isn't a new construction modular - it's a resale home. We have temporarily capped the open line, and have had a licensed plumber and a second state inspector out here to inspect the septic system and the plumbing again. There is no s-trap there or in the other guest bathroom, thankfully. We were not happy about the prospect of possibly having to replumb our whole system. And it looks like we won't. According to both the plumber and the inspector, all that needs done is to properly vent the bathroom through the roof. That should eliminate the problem with the sewage odor in the house.

Now - the odor coming from the outside is another issue. The previous owners of this place had a camper on the property (it's still here, it came with the house, and we do plan to remove it). They had the camper's black and gray tanks running to the septic via hoses going down into one of the openings in the top of the tank, since the camper was being used as living space. They also had a propane tank (yes, a home-sized tank) for the camper's cooking etc. The house itself is on natural gas. Anyway - the hoses to the septic from the camper had been disconnected and pulled out of the septic upon the previous owner's death. The cover was replaced improperly, and we (with the help of the inspector and plumber) replaced it properly. We were told that there may still be a lingering odor for a few days, but if there are still odors after a week or so then we need to have a septic company inspect for damage to the cover. This sounds plausible.

Any ideas about the mystery wet spot?

The bug up my butt about the whole odorous issue is this:
Why wasn't the venting issue caught at the first inspection before we bought the house? This is the discussion that I have been having with my husband, since he was present at the first inspection and he walked the house with the first inspector himself.

We looked at this place in January, and closed by the end of March. There was still close to 2 feet of snow on the ground, and I keep telling myself that this is why the septic wasn't inspected properly the first time. But that doesn't excuse the issues. I wanted to wait until either the snow melted or until we could at least clear the tank area to have that inspected. We didn't realize that the camper had been connected to the septic at all until May, when the snow was gone. Lesson learned: Don't go house hunting in the winter when there's a lot of snow on the ground. And sadly, I wish that my husband would learn that candy bars are an impulse buy - not houses.

Thanks for listening to my little rant, there... sorry... And thanks for your response! It's great to have a place like this message board to find answers to my questions when nobody else will help me! :D

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Originally Posted by RavenKnighte

Hey, Tom...
No prob. Like I said, I was born and raised in Hawaii and the codes change there every 10 years or whenever new developments in safety issues happen (I assume it is the same all over).

I don't know what the purpose is of the open line under the vanity, although regarding that, we suspected as you do - it was supposed to be a vent that was supposed to have been run through the roof that was never completed. It turns out that this is exactly the problem. It wasn't a cracked pipe or anything like that, as we had also suspected.

As far as a warranty goes - this isn't a new construction modular - it's a resale home. We have temporarily capped the open line, and have had a licensed plumber and a second state inspector out here to inspect the septic system and the plumbing again. There is no s-trap there or in the other guest bathroom, thankfully. We were not happy about the prospect of possibly having to replumb our whole system. And it looks like we won't. According to both the plumber and the inspector, all that needs done is to properly vent the bathroom through the roof. That should eliminate the problem with the sewage odor in the house.

Now - the odor coming from the outside is another issue. The previous owners of this place had a camper on the property (it's still here, it came with the house, and we do plan to remove it). They had the camper's black and gray tanks running to the septic via hoses going down into one of the openings in the top of the tank, since the camper was being used as living space. They also had a propane tank (yes, a home-sized tank) for the camper's cooking etc. The house itself is on natural gas. Anyway - the hoses to the septic from the camper had been disconnected and pulled out of the septic upon the previous owner's death. The cover was replaced improperly, and we (with the help of the inspector and plumber) went ahead and replaced it properly. We were told that there may still be a lingering odor for a few days, but if there are still odors after a week or so then we need to have a septic company inspect for damage to the cover. This sounds plausible.

Any ideas about the mystery wet spot?

The bug up my butt about the whole odorous issue is this:
Why wasn't the venting issue caught at the first inspection before we bought the house? This is the discussion that I have been having with my husband, since he was present at the first inspection and he walked the house with the first inspector himself.

We looked at this place in January, and closed by the end of March. There was still close to 2 feet of snow on the ground, and I keep telling myself that this is why the septic wasn't inspected properly the first time. But that doesn't excuse the issues. I wanted to wait until either the snow melted or until we could at least clear the tank area to have that inspected. We didn't realize that the camper had been connected to the septic at all until May, when the snow was gone. Lesson learned: Don't go house hunting in the winter when there's a lot of snow on the ground. And sadly, I wish that my husband would learn that candy bars are an impulse buy - not houses.

Thanks for listening to my little rant, there... sorry.... And thanks for your response! It's great to have a place like this message board to find answers to my questions when nobody else will help me! :D

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Raven, You asked,"Any ideas about the mystery wet spot?" If this is in the cabinet with the open pipe then water's backing up out of the pipe. If that's not the case then I would run water in the lavatory, drain the tub or do anything to make the wet spot appear. You must locate the source before you can repair it.
You also complained, "The bug up my butt about the whole odorous issue is this:
Why wasn't the venting issue caught at the first inspection before we bought the house? This is the discussion that I have been having with my husband, since he was present at the first inspection and he walked the house with the first inspector himself. "
The only possible answer is that the inspector was (1) incompetent and not familiar with basic plumbing practices, (2) He was in the contractors pocket and was what we call a "tame inspector" or (3) he was stoned out of his mind and thought everything looked just dandy. You choose between door #1, 2 or 3.
Good luck with the septic tank. Please keep me in the loop on this and let me know what turns up. Tom

Thanks for the suggestions, Tom. We did as you suggested, and we couldn't make the spot appear again ourselves. And then last night we found out what was actually causing the wet spot. Well, our dogs did. They were barking at the vanity cabinet last night. Turns out that the wet spot was caused by a critter going in and out of that open pipe. The wet spot was where it landed when it jumped off the edge of the open pipe. My husband had temporarily "capped" it off with duct tape, and the critter had chewed its way through. So this morning, I went and got a rubber stopper that fits snugly enough to cap that pipe until we get it properly vented. I did all the measuring for the materials to vent the pipe this morning after my trip to the hardware store up the road. I should have all the materials and be able to get going with this in a couple of days. So that's solved. Oh - the critter was dealt with.

As for the issue of the inspector - I have scheduled another home inspection by a team of reputable, state-licensed inspectors including a plumbing engineer and an electrical engineer, and a septic system inspector. I want to make sure that there are no more surprises.

Thanks again for your help! :D

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Originally Posted by RavenKnighte

Thanks for the suggestions, Tom. We did as you suggested, and we couldn't make the spot appear again ourselves. And then last night we found out what was actually causing the wet spot. Well, our dogs did. They were barking at the vanity cabinet last night. Turns out that the wet spot was caused by a critter going in and out of that open pipe. The wet spot was where it landed when it jumped off the edge of the open pipe. My husband had temporarily "capped" it off with duct tape, and the critter had chewed its way through. So this morning, I went and got a rubber stopper that fits snugly enough to cap that pipe until we get it properly vented. I did all the measuring for the materials to vent the pipe this morning after my trip to the hardware store up the road. I should have all the materials and be able to get going with this in a couple of days. So that's solved. Oh - the critter was dealt with.

As for the issue of the inspector - I have scheduled another home inspection by a team of reputable, state-licensed inspectors including a plumbing engineer and an electrical engineer, and a septic system inspector. I want to make sure that there are no more surprises.

Thanks again fo your help! :D

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Before I ran that vent I would send a snake down the open pipe. If your critter got in there and couldn't turn around to get out you'll have a dead critter blocking your vent. Cheers, Tom