Basement Venting Help

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rich0014

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Hello All,
I am a first time poster that stumbled across this forum in doing some research for my project. I did not find a question quite like mine so I thought I would post details of my situation and ask for help from the experts on this Board.

I am finishing my basement in Loudoun County VA and doing most of the work myself. I am getting the job permitted. I purchased the house with an unfinished basement and rough-in for a bath but I would also like to add a bar sink and dishwasher. I am generally pretty handy but hit a snag when the idea to add a wetbar came about. I thought I might share the existing lavatory drain with the bar sink/dishwasher but from what I gather that wont be allowed. In the picture below, the far side of the wall is the future bathroom. The near side is where I would like to put the bar sink in but I can move it within reason. There is also already a toilet and shower drain installed behind the wall. The pipe you see between the studs drains a powder room sink above.

So my questions are, can I tie in the bar sink/dishwasher to this drain pipe or can it only be used for the lavatory? Can I accommodate the bar sink with modifications (notice the main stack/clean out behind the foil insulation)? Lastly there is also a toilet above that appears to have a vent that I can tie into if possible.

Any help on the issue is very much appreciated. Thanks for your help,
Rich
sink.jpg
 

Terry

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We need a chart of all the pipes there first.
I only see the 3" stack to the right behind the foil and the lav rough in the center.
 

hj

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From the little you have described, it looks like you could install a "back to back fixture fitting" in place of the sanitary tee and connect the new sink to that.
 

rich0014

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Thank you both for the quick reply. A back to back fixture fitting is my ideal setup but through reading other posts I was not sure it was allowed since the orange pipe is the drain for the 1st floor powder room sink.

I do some sketchup work so here is my best try at a diagram which is not to scale but visually accurate.
First this is a 3 story house including the basement. I am only showing what I see in the basement and assuming everything else upstairs, behind walls, and in the basement floor is done correctly. This is essentially the sane angle as the photo above.

Purple - 2"
Orange - 1 1/2" - This pipe is the drain for a 2nd floor lavatory
Red - 3" Drain for 2nd floor toilet
Green 2" Vent for 2nd floor toilet
Blue 3" Drain for all fixtures on 3rd floor

If I can replace the tee between orange and purple with a back to back fixture fitting life would sure be easy.
Thanks again for your ideas and suggestions.
Rich

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Terry

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It looks to me that the downstairs lav is perhaps wet venting the shower and toilet.
Normally they only allow wet venting on the bathroom groups on the same floor, not the kitchen sinks and dishwashers and not the upstairs lav. You may want to ask the plumbing inspector how he feels about things.
It could be that the 2nd floor lav is wet venting the 2nd floor toilet, and that the downstairs vent it a vent. One way to tell is to run hot water from the lav upstairs and see which pipes heat up.
Since a kitchen sink does not normally wet vent a bathroom group, it's possible the inspector will want that off the 3" stack, and then vent either with the lav vent or an AAV.
 

rich0014

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Thanks again.
Orange heats up when 1st floor lav is running. Blue heats up with the 2nd floor lav or tub. Green is just a vent. Any final thoughts or should I give the inspector a ring at this point?
 

rich0014

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Thanks. That explains a big part of my confusion. I thought it seemed a little odd but did not want to make that conclusion and assume it was wrong when the house was built and supposedly inspected.
Should the basement drain shown in purple be tied to the green going up, and the 1st floor lav drain to red instead of purple?
 

Terry

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Should the basement drain shown in purple be tied to the green going up, and the 1st floor lav drain to red instead of purple?

Yes, it looks like the purple should tie to the green, but at 42" above the next floor. And yes, the 1st floor lav to the red.
Vents can tie in six inches above the flood level of the fixtures served.


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rich0014

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Terry,
Want to follow up and say thanks again for your sound advice and confirm you are 100% correct. Somebody messed up when the house was built 15 years ago. Basically, Green and Orange need to be reversed.

Also, for the record, the inspector told me that the bar sink would need to drain to the main stack (blue) but could use green for the vent once issues are corrected. I was told a back to back fixture fitting would not be acceptable.

Thanks for providing a great resource.
 
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