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.
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.