Which method involves venting a fixture or fixtures through the soil or waste stack?

Stack venting is the method that involves venting a fixture or fixtures directly through the soil or waste stack. In this technique, the venting pipe rises vertically along with the waste stack, allowing air to enter the plumbing system and maintain proper pressure. This ensures that wastewater flows smoothly and prevents any potential siphoning of trap seals that could lead to sewer gases entering the living space.

Stack venting is especially effective because it uses the same vertical space as the waste stack, simplifying installation and optimizing the layout of the plumbing system. This method helps to balance the pressure within the drainage system, allowing for effective drainage and minimizing the risk of clogs or backups.

In contrast, other methods like loop venting involve different configurations and approaches, while roof venting typically pertains to venting systems that exit through the roof for specific fixtures that require ventilation above the building. Direct venting is generally used in applications that involve combustion appliances rather than wastewater plumbing.