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Thread: Bath Remodel / drain and vent design

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  1. #1

    Default Bath Remodel / drain and vent design

    I have a 1975 built house where I want to remodel the lower floor bathrooms. At this point, all drain and vents are original to the home. The main stack rises out of the ground and then is a straight 3 copper vertical line right up through the roof. All bathroom plumbing on both floors is wet vented to this stack. In the second floor the toilet drains into a closet bend with a short 5 or so extension and then tees to the stack. That extensions contains a 1 tee that runs about 36 to the bathtub p- trap. About 18 above the main stack toilet tee another 1/1/2 tee serves a horizontal 36 line to the sink trap. On the first floor, One toilet connects in a similar fashion to the main stack with a 8 extension to the bend and also with a 1/1/2 bathtub drain teed into the extension before the connection to the stack. There is a second toilet served by a 3 pipe running about 48 teed directly in to the stack just below the other toilet . In addition to the above, which I know for certain, I have a sink that I believe simply drains horizontally 72 to the stack, probably 1 pipe. There is no vent attaching to the stack above the 2nd floor fixtures so I think it is simply wet vented also.

    I understand the concept of wet venting but wonder about the critical distances and other requirements that I am unsure of. That said, this is a vacation house and in 30+ years of very heavy weekend use often by a lot of people(including a washing machine also teed directly in that stack) there has never been the slightest issue with the plumbing.

    Now we want to remodel due to an accessibility need. The first floor tub is being changed to a shower. So I understand I need to upgrade to a 2 drain for the shower. Also a sink is being moved to where it needs to run an extra 3 feet horizontally or it could be run down through the floor and then horizontally to the stack, probably shorter than the original 72.

    Can anyone comment on the best arrangement for that sink in terms of drain and vent requirement?
    Would anyone comment of the current entirely wet vented configuration. I was surprised when I found no other vents on any of the fixtures.


  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
    Join Date
    Aug 2004
    Bothell, Washington
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    Wet vents occur between nearby fixtures on the same floor level.

    A lav with a toilet

    A lav with a shower

    Wet venting is not between two floors.

  3. #3


    Possibly I am not explaining clearly or miswording. In your picture the pipe labled vent stack serves as the combination drain and vent stack. The 2nd floor sink drians and vents directly to it, the toilet drains and vents directly to it with a 3 inch pipe, the tub drains and vents to that 3" toilet pipe just before it connects to the main stacl. That is the extent of the 2nd floor.

    The first floor is very similar, same vertical stack, toilet connected with 3" pipe, tub connected to toilet pipe just prior to main stack connection, a second toilet conected directly to stack just below other toilet wye. The only unknown for certain is that first floor sink which I strongly believe is connected with a simply horizontal line, (Just as the upstairs is except that the line would be a a bit longer)

  4. #4


    I saw on another post -------- "Venting must be on the same floor,
    You can't drop waste down the vent of a lower floor fixture."

    In essence. that is what I believe my situation creates. What am I missing? This was a home design/build used many times in our town and my original 1975 CO has plumbing rough in and final approval dates listed. Again this is all the original DWV layout.

    Now I am in the planning stages of the renovation and I am wondering if I have a bigger issue to deal with?

  5. #5


    perhaps a diagram will help. I'd really appreciate any comments. I am confused and a bit worried as I try to decifer all the posts about venting.
    The only uncertainty is the lower floor sink but I strongly believe it will simply be a straight 72" horizontal run as there is no eveidence of anything else in 2nd floor wall above or below in the crawl space, but I won't know till wall is opened. The main thing being chamged is the tub to a shower for accesibility reasons.
    This is in NJ, house was built in '75
    Attached Images Attached Images

  6. #6
    Plumbing Designer FloridaOrange's Avatar
    Join Date
    Dec 2005
    SW Florida


    I don't think that's legal as built under new codes. It's similar to a waste stack vent but under new construction codes toilets are prohibited from connecting to it and fixtures tie into the stack individually.
    Semi-professional plumbing designer
    Enjoying life in SW Florida


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