Builders install toilet vents as a part of the overall plumbing system. In many locations, building codes require a licensed plumber to design and install the vent system. Once installed, the code requires the system to pass an inspection.
Consult local building codes
Building codes dictate when and where a toilet vent is installed. They provide details, including the appropriate connectors, pipe and size of line. If your work isn't up to code, you must start again.
Consider the location
Toilets located within 6 feet of the main stack of the home require no further venting, according to SFGate. The main stack is a 3- or 4-inch line that connects directly to the sewer and includes a vent that extends through the roof. The fixtures in the home all drain to the main stack. Some homes have more than one main stack.
Add vents when required
Toilets outside the range for venting through the main stack require their own vent. Glue a sanitary reducing tee within 6 feet of the fixture. The new vent is usually 1 inch smaller than the line it's venting. Design the vent to run in a horizontal or upward direction to connect to the main vent stack. It must connect to the stack at a height greater than that of the highest fixture it's venting, generally the sink.