# 2010 Vancouver
A large amount of hydraulics testing has been done to evaluate the Manning’s “n” coefficient for profile wall high density polyethylene pipe with corrugated exterior. Testing has been done on the following diameters : 12, 15, 18, 24 and 36 inch. The earlier testing was done on smaller diameters and completed under full flow conditions with some hydraulic head at the inlet. The results of this testing showed an average Manning’s “n” of less than 0.012. A variation of the full flow testing involved a scenario in which the pipe was intentionally circumferentially shortened to determine impact on Manning’s “n”. The results showed at a lower velocity, the resulting Manning’s “n” was in some instances greater than 0.012. The majority of the values were below 0.012. More recent hydraulics testing has involved larger diameter pipe, 36-inches, under partial flow, gravity flow conditions with no hydraulic head. This testing showed an average Manning’s “n” value of less than 0.012. This hydraulics testing has been completed through several different programs. To date, there has not been a comprehensive document published which summarizes this research. This paper has been prepared to provide a summary of this hydraulics research and the results obtained.