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Mannings Value for Slotted PVC Pipe

Mannings Value for Slotted PVC Pipe

Mannings Value for Slotted PVC Pipe

(OP)
Any Ideas?

I can not find any sources.

RE: Mannings Value for Slotted PVC Pipe

What size pipe are you using?  This will, of course, affect the "n" you use.

I've typically seen something in the neighborhood of 0.01-0.016 used for 3"-8" pipe; 0.016-0.018 for 10"-12" pipe and 0.019-0.021 used for larger than 12".

Maybe some others can shed more light on this for you in the way of actual sources, of specific values, for varying cases.

H2H

RE: Mannings Value for Slotted PVC Pipe

(OP)
Concrete is 0.013, so how can PVC be higher than that.  And the pipes are 8-10 inches.

RE: Mannings Value for Slotted PVC Pipe

(OP)
The slots only account for 5% of the total area within on linear foot.  So the slots will make a slight impact but not alot.

RE: Mannings Value for Slotted PVC Pipe

(OP)
The rest of the area is smoother then a babies butt

RE: Mannings Value for Slotted PVC Pipe

Manning number of 0.009 is often used for typical PVC pipe, see question/answer #7 at this link
http://www.uni-bell.org/faq.html#top

Here is a reference (see page 14 of 19) to an assumed manning number of 0.02 for perforated pvc pipe
http://www.brisbane.qld.gov.au/bccwr/lib78/wsud_chapt5.6.1_to_5.8_bioretention_basins.pdf

More than double the unperforated value. Like you, I doubt if the manning number is that high.

www.SlideRuleEra.net idea

RE: Mannings Value for Slotted PVC Pipe

I agree with Uni-Bell that the n=0.009 is probably accurate for PVC flowing full.  Many suggest using 0.011 because Camp (circa 1950) found that n-values vary with depth.  According to his findings the max n/n0 = 1.2.  Which 0.009 * 1.2 = 0.011.  Whether Camp's study is applicable to smooth pipes is conjectural.  I tend to use n = 0.011.  For perf. or slotted pipe I might be temped to use n=0.012.

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