Right, nearly there; what are the units of distance (horizontal) and the units of elevation (vertical)?
Need to know to calculate the actual spill length of the pipe.

Separately, if the pipe does not have a constant cross-sectional area over its whole length the spill volume can still be calculated if we know the various cross-sectional areas (if it's a circular pipe, diameter will do). Does the pipe have a constant diameter over its whole length?