A vent terminal discharges sewer gas, so the code keeps it away from anything that draws air into a building. Under the IPC, what separation must be maintained between an open vent terminal and a door, openable window or air intake?
- AAt least 4 feet horizontally, or at least 2 feet above the top of the opening
Four feet horizontally is far too little separation, and 2 feet of height was the figure in earlier editions rather than the current one. This is the answer that catches plumbers working from an older memory of the section.
- BAt least 25 feet horizontally, with no height alternative permitted
Twenty-five feet with no height alternative overstates the horizontal distance and removes a compliance path the code actually provides. On a tight roof the height option is often the only workable one.
- CAt least 10 feet horizontally, or at least 1 foot above the top of the opening
One foot above the opening is not enough vertical separation to substitute for horizontal distance. The horizontal figure in this choice is right, which makes the wrong height easy to overlook.
- At least 10 feet horizontally, or at least 3 feet above the top of the opening
Why D is correct
The rule offers two compliance paths, and either one satisfies it: keep the terminal 10 feet away horizontally, or carry it 3 feet above the top of the opening. Sewer gas leaving a terminal is warmer and lighter than outside air and tends to rise, which is why extra height works as a substitute for horizontal separation.
What this question is testing
Whether the candidate reads a rule that offers alternative compliance paths as alternatives rather than as a single combined requirement, and whether they are current on the vertical dimension, which has changed across editions.
On the job
Rooftop equipment has multiplied, and a vent stack that was clear when the building was built often ends up next to a new outside air intake or a rooftop unit added during a tenant fit-out. When that happens the fix is to extend the vent upward rather than relocate it, because 3 feet of pipe is cheaper than re-routing a stack. Knowing both compliance paths lets you offer the cheap fix immediately.
Memory technique
Ten feet away or three feet over the top.
Exam tip
Rules written with the word or give you a choice. Pick the path that is cheaper on the job in front of you.
Where to look it up
Chapter 9, the location of vent terminal subsection. UPC differs on this point — follow the code your state has adopted.