Pipe Slope
Pipe Slope
(OP)
I would like to know some of the theory behind pipe size and it's minimum slope, particularily for 4" and 6" PVC SDR 35. It seems that every municipality has their own theory/regulations.
The reason I am posting this is I have a commercial office/maintenance building with 20 people, with two rest rooms, The sewer line from these is 4" with 1% slope with several sags and flat areas (which I feel is a result of the minimal slope), after 60 feet it changes to 5" terra cotta, again with a 1% slope. It picks up a few wash sinks and continues for 140 feet to the septic tank. The septic tank currently has 4.5 feet of cover and most likely will be replaced.
My thought is to run 6" PVC at 1% slope (grade set with laser), to reduce depth of installation and septic tank, and hopefully achieve a better flow.
Again I would like to hear the book theory as well as individual's theory and experience.
Thanks
The reason I am posting this is I have a commercial office/maintenance building with 20 people, with two rest rooms, The sewer line from these is 4" with 1% slope with several sags and flat areas (which I feel is a result of the minimal slope), after 60 feet it changes to 5" terra cotta, again with a 1% slope. It picks up a few wash sinks and continues for 140 feet to the septic tank. The septic tank currently has 4.5 feet of cover and most likely will be replaced.
My thought is to run 6" PVC at 1% slope (grade set with laser), to reduce depth of installation and septic tank, and hopefully achieve a better flow.
Again I would like to hear the book theory as well as individual's theory and experience.
Thanks





RE: Pipe Slope
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Pipe Slope
I concur on the bad installation comment.
Thanks
RE: Pipe Slope
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Pipe Slope
The slope of drainage systems is set by the local plumbing code which is may or may not have any science behind it. Here is a typical one:
Large Piping. Horizontal drainage piping larger than 3 inches but less than 8 inches in diameter shall be installed with a grade of at least ? inch per foot. For piping 8 inches or larger in diameter, the grade is determined by the number of drainage fixture units connected to the drain pipe.
RE: Pipe Slope
The slope for building drainage systems is set by the local plumbing code which is may or may not have any science behind it. Here is a typical one:
Large Piping. Horizontal drainage piping larger than 3 inches but less than 8 inches in diameter shall be installed with a grade of at least 1/8 inch per foot. For piping 8 inches or larger in diameter, the grade is determined by the number of drainage fixture units connected to the drain pipe.
RE: Pipe Slope
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Pipe Slope
"f) Small Piping. Horizontal drainage piping of 3 inches diameter or less shall be installed with a grade of at least 1/4 inch per foot.
g) Large Piping. Horizontal drainage piping larger than 3 inches but less than 8 inches in diameter shall be installed with a grade of at least 1/8 inch per foot. For piping 8 inches or larger in diameter, the grade is determined by the number of drainage fixture units connected to the drain pipe. "
It was further suggested that the information is available in the local plumbing code whereever the poster is located.