Trap to Vent Distance
(All of this information is taken from the IPC - International Plumbing Code)
One reason many plumbers fail inspection is because they either
Have too much distance from a p-trap to it’s vent
Or not enough distance.
In both of these situations the trap may lose it’s seal. How? Siphonage.
If siphonage occurs in one of your drains, it will cause sewer gases to rise up and it will smell very bad.
Minimum Distance - From Trap To Vent
The distance from trap to vent has to be AT LEAST twice the diameter. Anything less would be popularly known as the “Crown Vent”
Example of minimum distance (IPC Chapter 9)
2” Pipe diameter = 4” of Distance
3” Pipe diameter = 6” of Distance
Maximum Distance
The maximum distance is dependent upon 2 factors
Size of trap
Slope [ (1/8th) or (1/4) ]
For 3” and 4” pipe grading at a 1/4” per foot
