Help with pitch/slope from house to sewer

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by BajaJoe, Sep 27, 2006.

  1. BajaJoe

    BajaJoe New Member

    Sep 27, 2006
    :) Hi....

    This is my first post I have been lurking here a while but never posted.

    I am about to connect the main soil/drain pipe from my house to the city's sewer connection in the street, I

    plan on using 4" sched 40 plastic pipe, It will be a straight run (except for maybe a couple of 15 degree

    bends) but i think I may have a problem with the slope.

    The difference in height between the pipe exiting my house and the city sewer pipe is about 5 feet, and the

    distance between them is about 40ft, so If I connect them i'll end up with a slope of about 1.5" per foot of

    slope, and I have read that the optimal should be 1/4" per foot.... BUT... I have also read that this is

    just an old wives tale and that "any slope is good slope".

    So should I just run the pipe and hope I wont have any problems? (will I have problems?)
    or should I do the 1/4 per foot and near the sewer at the end do a real steep slope (maybe 75 or 85 deg)

    Thank you in advance for any input you can give me.. it is much appretiated !

  2. billsnogo

    billsnogo wannabe plumber

    Aug 7, 2006
    desk jocky at a bank
    brooklyn park mn
    I am just a novice, but from what I have been learning, if you do too steep of an angle, you will have all the water run down too fast leaving the solid waste to collect in the DVW pipe. Now I don't have any personal experience in this, so others will chime in.
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  4. Master Plumber Mark

    Master Plumber Mark Master Plumber

    Feb 6, 2005
    Sensitivity trainer.. plumber of mens souls
    indianapolis indiana - land of the free, home of
    some fall is good

    its best just to try to give the overall length of
    the pipe some fall......even it out through the overall run...

    not too little and not too much....

    what ever looks visibly the eye will work fine.....

    I like a healthy pitch, but you can go overbaord...

    of course .....the turd wont know the difference .....

    wether its flying fast or moving sloooow down to the sewer...
  5. Winslow

    Winslow Plumber

    Dec 30, 2005
    the goal is to get the water moving at 3 ft/sec down the drain line. The friction of the water on the pipe actually scours the pipe, which helps keep the pipe clean. 3ft/sec gives the pipe it's maximum scouring capabilities. A drain pipe sloped at 1/4/ft gives you 3 ft/sec on pipe sizes 3 inches and above.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona

    The actual slope is incidental as long as it is more than 1/4" per foot. But as a practical matter, since it is easier to dig a shallow ditch than a deep one, running it a the optimal slope and then dropping at the end is usually more practical. And you will not find 15, 75, or 85 degree bends.
  7. BajaJoe

    BajaJoe New Member

    Sep 27, 2006
    Thanks for all the Reply's

    Ok, so what i'm gonna end up doing is even it out thru the entire run, I don't mind digging a deep ditch (I need the excersice), I'll end up with about a 1 or 1.5" per foot of slope thru the entire lenght of pipe.

    What is the smallest degree bend that I can find ???
    (I would like something less than a 45)

    Last question....
    Would 2 45's cause problems in a slope like this?

    Thanks again for all your help, This is a great Forum !!!!!!!!!!!!!!!!!!!!!!!

  8. Gary Swart

    Gary Swart In the Trades

    Sep 1, 2004
    Yakima WA
    You will have more slope than you really need if you get it to 1" per foot. As far a bends are concerned, PVC pipe is somewhat flexible, if you widen the trench a bit where the bends are to be, the pipe can probably make the course correction without fittings. Any change in direction should be as gentle as possible anyway, so just do a tad more digging or dig a trench with an arc.
  9. kordts

    kordts In the Trades

    Oct 15, 2005
    industrial service plumbing foreman
    exurban Chicago
    You can't have too much pitch. The water doesn't outrun the turds. I would still run it 1/4" per foot. Then you have the height to make any offset needed.
  10. shacko

    shacko Master Plumber-Gas Fitter

    Jan 22, 2006
    Master Plumber-Gas Fitter
    Rosedale, Md

    You can have too much pitch, the water will outrun the turds. I don't know where you came up with this information; explain.
  11. markts30

    markts30 Commercial Plumber

    Sep 25, 2006
    Commercial Plumber
    Phoenix, AZ
    Run the pipe at 1/4" / ft. for it's run...
    Use 22.5 deg. fittings for the offsets and drop into the city line with a couple of 45's at the end....
  12. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    Funny thing Newton figured out...gravity works for water and turds with the same doesn't outrun the other. As stated, having too much velocity can erode the pipe, but it won't leave the turds behind.
  13. BajaJoe

    BajaJoe New Member

    Sep 27, 2006
    Great Info guys...

    Thank's for everybodys input it is very much appretiated.

    I plan to do it, this weekend, and with the help you guys have given me i'm confident I wont' mess up..... (at least not to bad) :D
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