Engineering Technical Note #12 ABOVE GROUND HDPE PIPE January 2009 Page 4 of 11 From Table 1, the 100 o F (38 o C) pressure design factor is 0.78, therefore the design pressure capacity, P (100 o F) would be the allowable design pressure multiplied by the design pressure factor: 160 psi. (0.78) = 125 psi.