3 inch to 2 inch

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by teke, Mar 17, 2013.

  1. teke

    teke New Member

    Messages:
    10
    Location:
    Massachusetts
    Question for the group. I presently have a double vanity that is drained by a two inch pipe. It is vented by a 3 inch DWV. The 3 inch waste passes through the floor and I would like to reduce it to a two inch pipe to connect to the main waste line. Would this be against code or do i need ti leave it as a 3 inch pipe. Also the distance to the waste line is around 6 feet
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,313
    Location:
    New England
    Do not confuse a vent with a drain...if it only serves as a drain for the vanity, it could probably be reduced to 2". But, it probably also has a connection to the toilet and tub, so, no, it must remain that size. And, if it is actually a vent for things below, it wouldn't pass code today, as you're using it as a drain and wet venting between floors is no longer allowed and needs to be at least that size to work well. Last kicker is that even in your own home in MA, it's illegal to do any plumbing...a pro would know what is required and how to do it properly. Many states allow a homeowner to do plumbing in their own home, but they all require a permit and an inspection. Failure to do so could get expensive and potentially dangerous.
  3. teke

    teke New Member

    Messages:
    10
    Location:
    Massachusetts
    Jim. Thank you for the quick reply. And I understand.
  4. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,395
    Location:
    Yakima WA
    I'm pretty sure that Massachusetts does not allow DIY plumbing at all. I'm not the plumbing police, but it would be wise to check this out...I've been wrong before, but if I'm correct you could be in deep doo doo if/when this is discovered.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,230
    Location:
    Cave Creek, Arizona
    Your description implies that you want to take a 3" drain line, reduce it to 2", and then connect it to a 3" line. if that is actually what you mean then the answer is NO, you cannot "reduce" a drain line in the direction of flow. The distance to the drain line is completely irrelevant, and while the vent MIGHT be able to be reduced in many cases, and it depends on the code and situation, it may be required to remain 3" all the way to the roof.
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