What is the primary defect you see in this photo?
a. A plumbing stack vent is too short.
b. Corroded flashing needs immediate replacement.
c. A combustion vent is located too close to a plumbing stack vent. The use of plumbing fixtures will pull the toxic products of combustion into the pipes from which it could enter the living space.
d. A combustion vent is installed too close to an attic opening (the ventilation fan opening). Under the right conditions, the toxic products of combustion might be pulled into the living space.