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Plumbing experts - question on sewer odor

joseywales

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Jun 23, 2017
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Southeastern, PA
Bear with me, as I post the complete picture:

I posted in another thread that we had a Navien tankless water heater installed, all good there. At the same time we moved the WH location, as well as the softener, etc. into one area, exactly where the waste pipe leave the house. At the same time, we reduced the 4" waste pipe to 3". It was 3" all the way into the basement, until about 10' from the cleanout, then it went to 4" into the cleanout. We wanted to push everything into a nook area of the basement and the plumber said there was no need for 4", so off we go.

Our washer/dryer are on the 1st floor - too long of a story as to why. And the back of the washer shares the same wall as our powerroom. Just behind the washer is that drain that runs into the basement, into a trap pipe, that extended below the drop ceiling - nice work :dunno: We shortened that to bring the trap above the ceiling.

Prior to any of this work, occasionally, we could smell rotten eggs in the laundry room. Faint, but I could tell at times, but it was rare. Humid days probably more so??? It doesn't seem to be any worse now.

Now, our sewer vent, you'll love this, is 15' directly in front of our front door, on the lawn. The cleanout and all of the plumbing we did is also located in the same area at the front of the house, in the basement. So it's a direct shot from our cleanout to the sewer line and about the same 15'. I can't honestly say I've ever smelled an odor from it outside. However, now I do at times and it was worse this morning, 9AM on a humid day.

After the work, I mentioned the odor, from the laundry, to the plumber and he made a comment I've heard before, "you don't have a vent for that laundry room". Actually, I've often wondered where the stack pipe for that powder room is. There are only two stacks coming out of the roof and I've never been able to route anything going from either of them to that powderoom. the plumber is a very good friend and partner of my nephew. He's not only licensed, but is a certified instructor and teacher on the trade, code, etc. He is also coming back to perform additional work. I'd be surprised if he made any mistakes, but we all take chances sometimes when ramming 10 pounds of **** in a 5 pound bag.

To recap:

- we reduced the 4" waste pipe to 3"
- We shortened the length of the Y and cleanout, but not by much.
- we shortened the drain from the washer upstairs.

Either the odor is coming from something that was done. Or, the lack of a stack and/or vent for the powderoom and laundry area, in combination with our changes, have made the odor worse. Maybe the shorter trap pipes, etc., aren't staying filled and trapping gas as well as they were?

Thoughts?
 
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jhelrey

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Sep 15, 2010
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MN
So the odor is coming from outside and inside? We had an odor from the outside and we swore they blocked off the vent pipe when we looked at the house. When we closed, it smelled horrible, every day. Long story short, a carbon filter fixed it.
 

Shiftless

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Mar 9, 2014
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East Bay SFO
Never heard of a ground level vent in the yard.

Maybe the OP is talking about a backflow prevention device.

Here's a pic of the type commonly used in my area. The second pic is debris (TP) left on the ground rather than back flowing into your downstairs shower pan if and when the main sewer line gets clogged.
 

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NUTTSGT

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Northern Central Ohio
Is there a stack that vents into the attic ?

Unless there is an open vent pipe or a dry trap, you shouldn't smell anything in the house.

I'm not a plumber nor have I seen it first hand but guys here (more knowledgeable than me) have mentioned before of a waste pipe that drains too fast and ***** the water out of the trap. ... creating a vacuum effect I'd guess from not enough vent.

I'd be curious if shortening up the length of the "Y" and the combination of going from 4" to 3" created an issue.
 
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joseywales

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Southeastern, PA
You know, I left one piece out and now I’m curious. After the work was completed, my upstairs toilets bowl didn’t fill completely. I figured it’d sort itself out, but googled the toilet in case there’s was a filter in there. See, the house came with Sloan Flushmate toilets. While Googling, I come to find that they were recalled. Turns out they have enough pressure to launch your ***. Well, not that much. But 300 of them exploded and 14 people have been injured.

I mention the toilets, because I installed the repair kits today, which consisted of a metal band for around the pressurized bladder and a regulator. Now the toilets have and flush with less pressure. Was the high pressure flush draining water from the traps, similar to what was suggested above? We shall see...well we shall smell!
 

Jackfre

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Dec 26, 2010
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N CA
Velocity can have an impact on waste lines. Lack of a vent in the laundry room would be the primary issue for me in this scenario. Is there a vent line from the laundry that ties into the main vent stack in the attic. It is common to gang vent pipes to eliminate roof penetrations.
 
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joseywales

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Southeastern, PA
Velocity can have an impact on waste lines. Lack of a vent in the laundry room would be the primary issue for me in this scenario. Is there a vent line from the laundry that ties into the main vent stack in the attic. It is common to gang vent pipes to eliminate roof penetrations.

That's what this plumber believed as well. There is no vent that anyone has been able to find. When the home was first built, 25 years ago, the layout was changed at some point after construction began. My basement joists are about 7.5 feet from the floor, same height as the garage. The garage was supposed to be mostly above grade, but ended up mostly below grade. the laundry was supposed to be in the basement, but ended up on the first floor. Something about the town complaining that the grade of the driveway/home was too steep, but that was possibly after the foundation was already poured?

Anyway, perhaps the rebuild on the fly caused an issue with where to run a vent for the laundry. There's a bedroom directly above it, a bathroom behind it, and finished living space on either side of it. I give that excuse, but only one of the 3 bathrooms have a ceiling vent fan, the other 2 have windows, which doesn't really cut it. And the 1 bathroom vent fan vents into the attic area and not outside of the house - terrible. When I rehab that bathroom, I'll solve that. Not sure the laundry vent will be as easy of a fix though.
 

Leaflessshadetree

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Don't ask.
My guess is that, as a result of shortening the lines, raising the trap and reducing the size of the pipe and of course no vent, water flowing from the rest of the system is sucking water out of the trap for the laundry room.
Adding a vent should fix it.
 
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joseywales

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Southeastern, PA
My guess is that, as a result of shortening the lines, raising the trap and reducing the size of the pipe and of course no vent, water flowing from the rest of the system is sucking water out of the trap for the laundry room.
Adding a vent should fix it.

I agree and the power flush toilets made it even worse. I asked if there would be issues, when they talked about raising the trap and they said no, but I knew better. Still, the trap was at least 8" below my drop ceiling and looked ridiculous, so I took a chance. As you said, the vent should be there and would solve the problem. Now I just have to figure out how we route a vent in there.
 

redmondjp

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Nov 25, 2014
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Redmond, WA
Look into an Air Admittance Valve or AAV - those can be used in some localities in lieu of an exterior vent line. I concur with the above posters that maybe a floor drain trap is getting sucked dry as it is acting as the vent.
 

yeldogt

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Jan 2, 2012
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The new water heater is getting it's intake air from outside ... correct?
 
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