Need help with basement drain/vent question...

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bsj8377

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Hello all! I've been a long time reader of this forum and have found it extremely useful with so many knowledgable people here!

I have a basement bathroom I'm trying to finish, and I have a question about the layout of the vent/drain system...

It's a ranch style home, and the following picture is a drawing of what's UNDER the basement slab...as if you were looking down from the basement floor:



That's the layout of what's there currently. I need to finish the walls in the bathroom, and I'm not sure how I can vent the bathroom. I'd rather not have to go through the upstairs wall all the way to the roof and add another vent there, so I was wondering if there is any reason I can't vent the basement bathroom out just above the sill plate under the deck outside on the north wall. This is where the basement bathroom exhaust fan is vented as well. The floor joists run N. to S. and sit on top of the sill plate. Currently the toilet flange and shower drain are installed, and there's a 2" stub out for the sink, so I need to figure out what I have to do to vent the system from here...will the following be acceptable:



Any suggestions or advice would be appreciated! Thanks!

Brian
 

bsj8377

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Ok, so the kitchen window rules out the under deck venting, and it seems that AAV's are code here, but there's the possiblility of smell from them...so what about this idea:

The wall that the fixtures are on (the West wall) in the basement is under the garage slab. So if I put a hole in the sill header plate I'll be in the garage. Can I run a pipe through that plate, and up the wall on the garage side into the attic, and from there over about 8' to the vent for the kitchen sink that goes out the roof...I could cut that vent in the attic and tie into it...this would allow me to NOT have to cut open any walls as well as NOT have to put another hole in the roof...

Would this be acceptable for code? For the pipe to be ran outside the drywall on the garage side? If so, would the above diagram be to code if I took out the side vent and went up to the roof?

My only other option, which is actually easier, is to run the vent along the north wall in the basement and attch to the main vent stack...there's a 1 1/2" vent line capped off there for this purpose, I could run 2" to it, but it's still going to be 1 1/2" up through the wall to where it connects the main vent in the attic. the horizontal span would be close to the 40' limit for 2" vent, but then it would turn into 1 1/2" for the vertical run to the attic...would that meet code? I'd rather do that if possible...here's a diagram:



I forgot to note that the washing machine in the basement also uses that same 1 1/2" vent going up through the wall that I would be tying into...if that makes a difference...

Anyone? Thanks!

Brian
 
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hj

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IS this bathroom something you just added? Otherwise whoever roughed it in should have made provision for a vent connection at the ceiling somewhere.
 

bsj8377

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Yes, we just added it...the house was built in 1988 so I don't know what was code back then...I'm just trying to find the best way to get it done without having to tear out finished spaces above, but it also has to work.

As for rough in, the only other thing I can see in the basement is some sort of metal oval shaped pipe that sticks down in one of the joists, has a piece of bubble wrap shoved up inside...it's very close to the chimney...I assume it's a secondary vent that goes up but I never looked up inside it. It's probably 8-10" long and 2" wide or so...guess I could try to find out where that goes?

Idk how I'm going to do this without tearing out finished space...
 

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Ok, so i went up in the attic to see how the vent was situated...there's a 3" vent through the roof, with a 3" to 1.5" reducer on it which goes to the kitchen sink. Now, I could definitely tie into that if I can get my 2" vent up through the wall from the basement...HOWEVER, the wall is directly underneath a truss. Cutting the truss is not an option, so I wouldn't have any choice but to put the vent outside the wall on the garage side...but I need to know if this would be against code? It seems that it's my only option, other use an AAV which seems to be an absolute last resort.
 

Cacher_Chick

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The vent can go vertically up through any first floor wall wherever it is the most convenient. Sometimes we resort to running the pipe up through the back corner of a closet and then frame and drywall around it if it is desired. Any section that is routed horizontally must be pitched to drain, and there can be no configuration of pipe and fittings that would prevent the vent from completely gravity draining rainwater and condensation. Look for an interior wall where the framing will not contain any obstructions such as other pipes. 2" pipe can be fit up through a finished 2x4 stud wall without removing any of the wallboard given some care.
 

bsj8377

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The vent can go vertically up through any first floor wall wherever it is the most convenient. Sometimes we resort to running the pipe up through the back corner of a closet and then frame and drywall around it if it is desired. Any section that is routed horizontally must be pitched to drain, and there can be no configuration of pipe and fittings that would prevent the vent from completely gravity draining rainwater and condensation. Look for an interior wall where the framing will not contain any obstructions such as other pipes. 2" pipe can be fit up through a finished 2x4 stud wall without removing any of the wallboard given some care.

Thanks for your reply!

An interior wall is not an option as there arent any in this open floor plan. The wall that separates the garage from the kitchen is my only option, however, there is a roof truss directly on top of that wall...so if I run the pipe inside that wall, I'll have to exit that wall before reaching the ceiling in the kitchen then continue into the attic to tie into the 3" vent that goes through the roof. Does code prevent me from exiting the wall before getting to the attic?

That wall is also insulated, so I'd have to remove the drywall on the garage side most likely to do this...that's why I was wondering if code permitted the vent line to be ran NOT inside the wall, but just outside the drywall on the garage side. I could just box it in and drywall as you suggested you sometimes do with the closet...the only difference being that the garage isn't normally a heated space...I don't know if that matters...

Also, it's been brought to my attention that I may have the vent in the wrong place in the drain line, it was suggested that the toilet HAS to be vented downstream (between the toilet flange and the main drain), where my vent line is actually "behind" the toilet...can anyone confirm this? I couldn't tell from the code...see picture:


 
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bsj8377

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Ok, I actually found a couple of old pictures showing the drain lines that were put in...the first show the section with the backwater valve, the toilet flange, and at the very top you can see the stub-out for the vanity and vent...





The second shows the stub-out for the vanity and vent better...





Can anyone confirm whether this will or won't work...? And I apologize for my drawing, the toilet flange is actually before the last 45 degree bend, not after it...

Thanks!

Brian
 

bsj8377

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So I've been up for hours trying to find a solution...it seems ALMOST everyone is saying the same thing...that this is an unvented toilet and it will have problems. I'm sick to my stomach right now...this is much worse than the venting problem...

So from what I can tell, the sink/shower/vent setup is ok...but it would need to enter the drain line AFTER the toilet...like the following diagram...




I "believe" this to be a valid design...but it's ALOT of re-work...the concrete has to come back out in a big area...

One other thought I had...could I leave it as is, except install a "y" in between the toilet flange and back water valve and run the 2" outlet straight to the wall and tie it into the sink/shower vent line up by the floor joist before it heads up to the attic. This would require alot less concrete work...but I don't know if this is allowed? It would essentially be a 2" dry vent coming right off the main 4" drain line...is this allowed?

 

Soapm

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Im no plumber, no nothing about plumbing and am the last one you should take an plumbing advice from.

Having said that, I was watching this old house or something like that and saw them use a device like this in a situation similar to yours. It keeps you from having to tear out all your cement and from running pipes up all your walls. You can insert these with a short pipe and hide them in the wall (I think). http://www.*******************/autovent.html

Looks like the link gods got me so do a search for Auto Vents - Air Admittance Valves - Home Sewer Vents and the one I saw used was "Air Admittance Valves by STUDOR®".
 
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bsj8377

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It's my understanding that the AAV's still require a vent to alleviate positive pressure... from what I have been told, the vent HAS to be AFTER the toilet, not behind it as mine is...if the direction of the flow was reversed and went from the toilet to the sink to the shower then to the main drain, then my setup would be valid...however, since it goes the reverse of that, I've been told that my setup is incorrect and that the toilet will most likely not work properly and I'm trying to confirm that...if it needs fixed I need to do it now...not after the rest of the bathroom is installed...
 

Cacher_Chick

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Your vent is washed by the lavatory, and will prevent the other fixtures from siphoning, so I would not be overly concerned about the in-floor plumbing.
You should be allowed to run the vent out the wall and up the exterior or garage in many places. Check your local code or feel out your plumbing inspector for a worthy opinion on that. You will need to be sure to make the size vs. Distance for overall length. Some places specify that a certain percentage of the vent piping must be vertical, with only a smaller amount of horizontal vent being allowed.
 

bsj8377

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Your vent is washed by the lavatory, and will prevent the other fixtures from siphoning, so I would not be overly concerned about the in-floor plumbing.
You should be allowed to run the vent out the wall and up the exterior or garage in many places. Check your local code or feel out your plumbing inspector for a worthy opinion on that. You will need to be sure to make the size vs. Distance for overall length. Some places specify that a certain percentage of the vent piping must be vertical, with only a smaller amount of horizontal vent being allowed.

Thanks so much for your reply...I've spent so much time overnight trying to figure this out that I'm starting to lose my mind! Understood on the vent sizing and length restrictions, I'm well within spec there. And I too believe that the vent will do what it needs to in it's current location with regards to siphoning. My only concern now is the toilet. I've spent the last 18 hours scouring the internet, looking at hundreds of diagrams and couldn't find one that was like my current in floor piping...I understand it's not right...but at this point, I just need to maybe temporarily install a toilet to see if it works. The only concern here (I think) is that since there's no downstream vent (other than the main stack many feet away), that positive pressure could build up not allowing the toilet to drain properly/pull waste through it's trap properly. I can understand that concept where the toilet has a "run" before it reaches the main drain...but if it empties directly into the main 4" drain like my current in floor plumbing, then I "think" that the only concern here would be the siphoning and that should be covered by my current vent.

I'm going to buy a toilet (need a new one for this location anyway), put it in, and see what happens. I "think", I hope, it works just fine...I'd really rather not tear out all that concrete again...

Thanks again for the reply!

Brian
 
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