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    jiffypop's Avatar
    jiffypop Posts: 3, Reputation: 1
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    #1

    Mar 25, 2014, 10:09 AM
    Is there a maximum slope for a toilet drain?
    Want to install a new drain line for a toilet, but it would have a slope of 7/8" per foot. Code only requires that slope be at least 1/4" per foot. Want to know if using this much steeper pitch would create flow problems. Thanks.
    massplumber2008's Avatar
    massplumber2008 Posts: 12,832, Reputation: 1212
    Senior Plumbing Expert
    		  
    #2

    Mar 25, 2014, 10:39 AM
    Hi JP

    A 1/4" to a 1/2" per foot of pipe is ideal. I wouldn't want to run a 100 foot run of pipe at 7/8", but if we are talking say 5 or 10 feet maximum then you should be just fine here!

    Mark
    speedball1's Avatar
    speedball1 Posts: 29,301, Reputation: 1939
    Eternal Plumber
    		  
    #3

    Mar 25, 2014, 12:57 PM
    Too much slope and the water runs so fast it leaves solids behind. Too little and the solids drop off and the water runs out. When I was out there we ran 2" at 1/8" to the foot and 3 and 4" at 1/4" to the foot although I remember running 10 and 12" cast iron mains at 1/2" to the foot. Regards, Tom
    jiffypop's Avatar
    jiffypop Posts: 3, Reputation: 1
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    #4

    Mar 25, 2014, 07:17 PM
    Thanks a lot! The new PVC drain line would only run 5 to 6 feet to the old cast-iron drain, so I'll go ahead with the 7/8" pitch.
    jiffypop's Avatar
    jiffypop Posts: 3, Reputation: 1
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    #5

    Mar 25, 2014, 07:20 PM
    Quote Originally Posted by speedball1 View Post
    Too much slope and the water runs so fast it leaves solids behind. Too little and the solids drop off and the water runs out. When I was out there we ran 2" at 1/8" to the foot and 3 and 4" at 1/4" to the foot although I remember running 10 and 12" cast iron mains at 1/2" to the foot. Regards, Tom
    I'm curious as to why the code doesn't reflect this. Seems like it would be important to impose a 1/2" per foot maximum to reduce the chances of these kind of flow issues. Thanks again!
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