What type of waste pipe discharges through an air gap into a properly trapped and vented fixture?

The type of waste pipe that discharges through an air gap into a properly trapped and vented fixture is the indirect waste pipe. This configuration is specifically designed to prevent any backflow or contamination of potable water systems. The air gap creates a physical separation between the waste line and the fixture, ensuring that wastewater does not have the potential to siphon back into the clean water supply.

In plumbing systems, indirect waste pipes are often used when a direct connection is not permissible or feasible, allowing for safe and effective waste management. The use of an air gap not only enhances safety by preventing contamination but also complies with plumbing codes that mandate such measures in specific scenarios.

Other types of pipes mentioned, such as direct waste pipes, greywater pipes, and sanitary waste pipes, do not serve the same purpose. Direct waste pipes connect directly to drainage systems without such safeguards, while greywater pipes specifically handle wastewater from non-toilet fixtures. Sanitary waste pipes deal with the overall collection of sewage, but they typically do not involve the safety mechanisms provided by the air gap that characterizes the indirect waste pipe.