What is volume of water in a 34 inch pipe 5 feet long?

If it is full, which is unlikely unless it is vertical, then it is the volume of the pipe computed using consistent units.

V (πr2h) where r is the radius and h the height (length). Taking the radius to be 34/2 17 inches or 1.417ft, r2 2.007ft2 so that

V π(2.007ft2(5ft) 31.526ft3(rounded)