On one of my 11 month warranty inspections I found this. What you are seeing is a water softener drain line tapped into a plumbing vent in the attic space. Why this is a no no.
1. The potential for gas fumes to travel from the plumbing system to the water softener and contaminate your potable water. Ick! The drain should have an air gap to prevent this.
2. Obviously tape isn't the proper connection technique. This was located above the kitchen area. If this were to leak or separate it would flood their kitchen and cause all kinds of damage!