Moving a cast iron main vent..help?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by drector30, Apr 7, 2006.

  1. drector30

    drector30 New Member

    Messages:
    2
    I am remodeling a house I just bought and I am moving the bathroom and expanding the kitchen. I need to move the cast iron main vent 4' to the new common wall between the new expanded area and the new bathroom location. Can I run the vent horizontal for 4' in the basement as long as I install a cleanout cap? Or do I have to move the main vent in the basement concrete floor 4'? Also, can I run two pvc pipes that are equal in area to the original cast iron pipe(from the floor up) so I do not have to build a 6" wall to accept the main vent pipe?
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,631
    Location:
    Cave Creek, Arizona
    pipe

    The way you describe it, you can just offset the pipe through the room, but there may be something you are not telling us, such as what happens to the pipe after it goes through the ceiling. Most inspectors would not go for the multiple vent system, and the only single pipe that could be replaced by just 3 smaller ones would be a 4" vent replaced with two 3" ones. Any other combination would require three or four pipes to equal the area, not the diameter, of the removed pipe.
  3. drector30

    drector30 New Member

    Messages:
    2
    More detail

    This is a single story ranch with basement. I believe the pipe goes straight through the roof for venting. It looks like a 5" or 6" cast iron pipe. The wall that I am removing with it in is a 6" wall. What I am questioning is can I run the pipe horizontal just below the floor joist (in the basement) to the new common wall 4-5' away, then run it straight up and out the roof? Also, I am questioning do I really need a 5" or 6" diameter pipe for a main vent? I only have one kithchen and one bathroom in the entire house. I know that in the 40's when they built this house everyone tended to go overboard on sizing everything. Another bit of information...when this vent was installed the house was on septic and now it is on city sewer. I do not know if that makes a difference or not.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,631
    Location:
    Cave Creek, Arizona
    vent

    There are two different factors to consider. One is that your area might require the vent to be full sized all the way to the roof. The second is that you almost always have to equal the area of the main sewer with the vents through the roof. If you only have one, then it would also have to be full sized.
  5. size of vent

    depeding on where you live, I am prety sure you could
    at least shrink that pipre to one 3 inch pvc for the vent out
    the roof....

    In the midwest, Indiana, we can take one 1 1/2 pvc pipe out the roof
    for a house lots bigger than you described....


    air is air and it does not know wether it is passing through a 4 inch
    or a 1 1/2 inch pipe.... I think the word is static pressure??

    It stays close to the same in the plumbing system with either size vent...
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