# Draining a sink into the vent pipe?



## vseven (Dec 2, 2009)

I have been working on my basement for 8+ months and I'm getting ready to start plumbing. Basically the building owner roughed in a bathroom in the basement and put in a toilet during construction (assuming to save on a Porto potty). There are two "drains" in the floor on the right, the one "closest" when you look at it is actually a clean out (I opened it up and verified water from upstairs flows across the bottom of it). The back right drain (corner) is assuming for a shower (but almost unusable because of how close to the toilet it is which is why I'm not bothering). The stack on the back left appears to be the vent for this clean out and I can see it on the roof almost directly above where it is in the basement.

So I've attached my plans for the room. Can I use the vent pipe as my drain? There is no real other option in this room and I'm assuming that's why they stubbed it out. I figured I'd run a 90* through the wall from the pipe right to my sinks drain. Do I need to add a separate "vent" above where the stub is also or will this short run be ok?

-Allan


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## Alan (Apr 12, 2006)

Since I don't see any other pipes coming out of the concrete, i'm going to guess that it was just roughed in as a half bath, otherwise you'd have a square box somewhere in the concrete close to another pipe coming up maybe 6-8" away from the box. That would be for a shower or a tub/shower.

The pipe in the back on the right, I would guess is the toilet vent. That needs to exit through the roof either by going all the way out or intersecting with another vent somewhere else in the house.

The one on the left isn't a 'vent for the cleanout' it's a lavatory rough in.

Your drawing shows the lavatory too close to the toilet. Your minimum clearance is 15" from center of toilet to a sidewall, cabinet, or countertop edge. I'd reccomend 16 or 17 because 15 feels tight.

How are you planning on getting the lavatory drain from where it's at to the spot where you have the cabinet drawn? ? ? :huh:


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## vseven (Dec 2, 2009)

Are you sure the back right is a toilet vent? I ask because the house was built in 99 and I've owned it for the last 3 years and have never had a issue with the toilet.....it works fine. I really think it was designed for a stand up shower and the vent for this set of pipes is the one on the back left. Also if the pipe on the back left isn't made for a drain why did they put a stub out on it? 

For the drain I figured I'd put a trap and point it to the left wall, out the wall, and to the existing stub out. The room on the left is the utility room (furnace, HW tank, etc) and I was possibly going to put a utility sink in that corner anyway.

The original builder has been a pain to work with...everything I ask for is a labored process to get a answer. I've been waiting 3 years for the blueprints...it took me months to get the paint colors (of which there were only 4 colors....) so I'm pretty doubtful I can get the original piping layout. I am confident that the front right plug in the floor is a clean-out...both the toilet down here and the bathroom above it go through that and the water floow is from left to right (right goes out of the house) so I'm assuming this is the last clean-out before it exists the house. The left to right pipe is a good two feet below the floor level.


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## TheEplumber (Jul 20, 2010)

Remove the cap from the pipe on the right and pour water down it. If it keeps a trap seal then its for a shower/tub. Could even be a floor drain that didn't have the body installed. I bet its a wc vent though.
Alen's correct on the toilet too. You need more room. Also, you need to keep the floor cleanout on the right accesible. Move that wall out to the foundation


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## vseven (Dec 2, 2009)

Removed the cap from the back right and it does appear to be a drain. Pipe drops down about 18" then starts to turn left towards the toilet Right before it starts to turn is the water level. I poured about 3 cups of water down and the level remained constant.

Also attached is the current progress. The room is actually a little wider then the plans show. Also the reason the wall wasn't moved out to the foundation is because all of the upstairs plumbing is right above that crawl space on the right (toilet, shower, and jacuzzi tub supplies, drains, and electrical). I did not want to build a room under all that.

So does this mean the pipe on the back left is the vent? And if so can I use it as a drain like I had planned?


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## Alan (Apr 12, 2006)

It doesn't make any sense to me that the line with the stub on it is a vent. Obviously it has a vent attached to it, but the way plumbing works, that wouldn't be a vent for the entire system down there. The toilet needs a 2" vent, and i don't see one, except for the one in the back on the right.

This is too confusing without being able to be there and investigate it. Why don't you call the person who put the plumbing in? You say the owner did it, does he have documentation where it was inspected and signed off? You sure he did it right?

That 'drain' in the back on the right would never line up with a shower base if you were to put one in the corner. Not even close. Thats why I don't think it's a shower drain. Maybe a floor drain like eplumber said.


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## TheEplumber (Jul 20, 2010)

Is the lav vertical drain and vent 2" or 11/2"? Toilets should vent on 2". I am allowed to wet vent that toilet as shown if that lav is 2". It will work tho on 11/2" - it just undersized.


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## vseven (Dec 2, 2009)

This was a house built in a small development so the developer built the house and sold it and on the ad said it was roughed in for a full bathroom in the basement. I bought it from the initial first owner (who never did anything in the basement). I'm sure it wasn't done right...I've found lots of things that aren't "right" but work ok. Most of the sweated connections on the copper look like a monkey did them...gobs of flux and solder dripping off and most are corroded. Next door neighbors house has drain rated PVC used for a bunch of supplies (and has had a couple burst). All the same developer/builder.

In regards to the drain lining up....I looked at a couple 5' tubs and the drain, with a 1" wall along the right foundation, would fit perfectly (with a small wall spacing it out from the back wall). It just would be a bit close to the toilet and it would cover the clean-out. I found some stand up showers that also would fit but again none looked right with the toilet being so close and I didn't want to break out the concrete to relocate which is why I'm down to a half bath (on top of the aforementioned plumbing upstairs). 

So I did some more testing. I filled the toilet tank with water then pulled the cap off the stub in what I think is the vent (back left). I can smell sewer gases from that vent and there was a little pressure in it (slowly pushing air into the room). I had my wife flush the toilet and as the water went down the pressure in the vent switched and it began to suck air in. After about 6 - 7 seconds it stopped and flipped again and slowly pushed air into the room.

I'm now pretty confident that this is the vent for this "set" of drains (the toilet and the "shower"). Does this make sense based on my testing? If so can I use this stub out and put my sink drain into it? It appears to be a 2" PVC from floor to ceiling.

-Allan


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## frank313 (Jun 9, 2010)

*draining a sink into the vent pipe*

as e plumber said above it's called wet venting. it's legal, so your ok.


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## vseven (Dec 2, 2009)

Cool....thanks everyone. Very helpful. I'll go ahread with my plans of draining/venting through the existing pipe. Now to study up on Pex....

-Allan


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## Alan (Apr 12, 2006)

frank313 said:


> as e plumber said above it's called wet venting. it's legal, so your ok.


That depends entirely on the sizing of piping and fittings used below the slab too.


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## rudolph58 (Mar 11, 2009)

hello,
You can wet vent the toilet with the lav and tub/shower since they are less than 4 DFU's. So as long as the lav drain/vent is 2" and it terminates above the roof then go for it!

PS:You need at least a 30" opening for the toilet


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## Jim F (Mar 4, 2010)

This was done by the plumbing subcontractor when my addition was first built. I don't see the need for the downhill slope but that is essentially a sink drain going into a vent stack.


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## vseven (Dec 2, 2009)

I can go with a 18" sink and I think I'll be ok on the width for the toilet. I'll mock it up with cardboard both with a 18" and a 24" and see how it looks.


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## Alan (Apr 12, 2006)

Jim F said:


> This was done by the plumbing subcontractor when my addition was first built. I don't see the need for the downhill slope but that is essentially a sink drain going into a vent stack.


That is not a legal connection. :no:


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## The Engineer (May 4, 2010)

Jim F's diagram might be fine without knowing the configuration of the piping outside of the view of the picture. What that picture shows, is a "stack vent". The continuation in an upward direction of the waste stack for a toilet may serve as a vent for the toilet and the waste for a lavatory. as long as no other fixtures connect into that stack on upper floors, it looks legal.


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## vseven (Dec 2, 2009)

vseven said:


> I can go with a 18" sink and I think I'll be ok on the width for the toilet. I'll mock it up with cardboard both with a 18" and a 24" and see how it looks.


I should say that this will not be inspected, I'm doing it all on my own, but I would like it to conform as close as possible to code just simply so I won't have as many problems. If a 24" looks better but doesn't leave a lot of space then so be it....there are 2 1/2 baths already in the house so I won't be too concerned especially for a basement.


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## The Engineer (May 4, 2010)

Vseven,

Just to confirm your situation, and I do this everyday, the line in your picture on the left is definately a roughin for a lavatory. From the Tee down is waste, from the Tee up is vent. The waste down also serves as a "wet vent" for the toilet and shower rough-in. Thats why you get airflow when the toilet was flushed, you are prefectly fine connecting into this for your sink. The line on the right is definately a rough-in for a shower or bathtub. When they placed those lines under the slab they didn't have any type of shower or bathtub to determine the final location of the trap below the floor, and just placed it "anywhere" because it wasn't their problem to fit a shower stall or bathtub to it. What they should've done, was leave a section of the floor open around that pipe so the pipe could be moved in the future to line up with the drain location of a specific model shower or tub that would be installed here. But that would've been more work on their end to box out a small area prior to pouring the slab.


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## rudolph58 (Mar 11, 2009)

I'm confused.Are we talking about Jim F's picture or vseven's mock up ? Jim F dirty arm off of the stool vent is not legal for the lav drain.It needs to run at the height of the lav waste less the 45 offset.You are creating a illegal S trap


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## TheEplumber (Jul 20, 2010)

rudolph58 said:


> I'm confused.Are we talking about Jim F's picture or vseven's mock up ? Jim F dirty arm off of the stool vent is not legal for the lav drain.It needs to run at the height of the lav waste less the 45 offset.You are creating a illegal S trap


I'd be tagged and fired for that lav piping:wink:


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## the_man (Aug 14, 2010)

rudolph58 said:


> I'm confused.Are we talking about Jim F's picture or vseven's mock up ? Jim F dirty arm off of the stool vent is not legal for the lav drain.It needs to run at the height of the lav waste less the 45 offset.You are creating a illegal S trap


I agree with you and EPlumber, but 45 degrees from horizontal is still horizontal, so how is it an s trap?


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## Jim F (Mar 4, 2010)

rudolph58 said:


> I'm confused.Are we talking about Jim F's picture or vseven's mock up ? Jim F dirty arm off of the stool vent is not legal for the lav drain.It needs to run at the height of the lav waste less the 45 offset.You are creating a illegal S trap


Yep someone should have told that to the plumber who installed it in 1990. He's dead now so it's too late. As I posted, the down slope doesn't belong. The 3" vent stack it taps into serves the toilet and had a branch vent tapped into it in the attic. There is no second floor there, just the vent to the roof. I didn't consider that there may be any syphoning action going there so I left it as is. I'll have to look and see if the vanity p-trap syphons. If so I'll open that wall back up and reposition it. 

I only posted the picture to show the OP that what he was proposing could be done. I forgot they were called dirty arms. I didn't mean to confuse the thread.


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## TheEplumber (Jul 20, 2010)

the_man said:


> I agree with you and EPlumber, but 45 degrees from horizontal is still horizontal, so how is it an s trap?


Doesn't directly answer your question but quite simular


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## Alan (Apr 12, 2006)

the_man said:


> I agree with you and EPlumber, but 45 degrees from horizontal is still horizontal, so how is it an s trap?


Aside from the technical image provided above, our code calls for the vent to come off the TOP of the trap arm.

Not sure why they would do that in the first place. It's more difficult to line out, cut holes, and an extra fitting in there too. :huh::huh::huh:


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