question about slope

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by jjgmorgan, Mar 22, 2014.

  1. jjgmorgan

    jjgmorgan New Member

    Messages:
    11
    Location:
    Tennessee
    Is there a maximum vertical drop distance allowed for a drain pipe? I have a 2" drain pipe for my kitchen sink. Is runs 10 feet at 1/4 per foot slope. I now need to drop vertically to the 3" main drain line.
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,607
    Location:
    Cave Creek, Arizona
    If there were, the skyscraper office buildings would not be able to have plumbing installed.
  3. asktom

    asktom Member

    Messages:
    552
    Location:
    Victor, MT
    After the vent there is no limit on steepness of slope, before the vent (trap arm) is a different ballgame with different rules.
  4. jim mills

    jim mills New Member

    Messages:
    141
    Location:
    nebraska
    Don't go over 90 degrees! :p
  5. jjgmorgan

    jjgmorgan New Member

    Messages:
    11
    Location:
    Tennessee
    Lets say a drain pipe runs 8 feet, you have a 2" slope. The pipe then goes 90 and drops two feet. Another 90 puts it running horizontal again. What would be the slope at that point for another 8 foot run? It it going to be 2" or 4"?
  6. jim mills

    jim mills New Member

    Messages:
    141
    Location:
    nebraska
    2" miinimum (1/4" per foot)
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,990
    Location:
    New England
    Or, IOW, you need a MINIUMUM of 1/4" per foot on any horizontal run - essentially forget the verticals or diagonals, or whatever, as they ARE above the MINIMUM...the slope is for ALL parts of the system. Nowhere can it be without slope downwards, and should never try to go up again unless you have a pump there.
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,607
    Location:
    Cave Creek, Arizona
    quote; What would be the slope at that point for another 8 foot run? It it going to be 2" or 4"?

    Every horizontal section is computed individually, therefore its "minimum" slope would be 1/4"/ft, or 2". The original 8' section has NOTHING to do with it, once it changed elevations.
  9. jjgmorgan

    jjgmorgan New Member

    Messages:
    11
    Location:
    Tennessee
    Thank you, that was well put, I understand.
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