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

1. Have too much distance from a p-trap to it’s vent

2. 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

1. Size of trap

2. Slope [ (1/8th) or (1/4) ]

For 3” and 4” pipe grading at a 1/4” per foot

Venting Requirements - Rules of the Santee

Rules of the sanitary tee

• Sanitary tees or “Santees” are used in many different positions. However, if you don’t have an understanding about how santees actually work, you might install one incorrectly.

• Below is a Santee in the vertical position. In this situation the vent would go to the top of the fitting.

This next situation, the Santee is upside down with the side going to a branch and picking up an individual vent at the bottom.

In this situation, the Santee is located on it’s back. The vent would connect to the tee side. A fixture may not drain into the vent of a Santee in this position.