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Can anyone tell me the formula for calculating sewer flow rate in a gravity oval sewer. What I'm working on is old gravity sewers in Newark, NJ. Combined sewer, some oval some teardrop shaped. I found circular and rectangular but nothing on oval and teardrop. Thanks.

RE: Formula

You use the Manning's equation.
You will have to draw the ovals  on paper and measure the wetted perimeter and calc. the area with planimeter to get the Hyd Radius. ask someone in the drafting dept if they have done this. I will contact some people I kknow in Mpls to see if they havethe numbers. I do have numbers for brick egg sewers.

Richard A. Cornelius, P.E.

RE: Formula

elliptical pipe design tables are available in the concrete pipe design manual:


not sure what size(s) you need, but combined sewer sizes are probably in these.


RE: Formula

I have the numbetrs for cemeny oval pipes
12 inch cement oval, Area- .83 Sq. Ft., circum. = 40.19 inches
15 inch cement oval, Area = 1.27 sq. ft.Circum. = 49.64 inches
18 inch cement oval, Area = 1.81 sq. ft. Circum. = 58.21 inches.
These are pipes that look like drain tiles and are 100 plus years old. They tend to deteriorate with a pattern that reflect the compaction effort during the construction  of the pipe. The inside of the old pipe takes on a look like a corrugated pipe with a long span from peak to peak. This is the stoke of the machine that made the pipe. I will try to post some drawings of these. These drawings and numbers are courtesy of the City of Mpls., Sewer Maintenance Dept. At least that is what it was called back when I was in charge.  

Richard A. Cornelius, P.E.

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