Which type of pipe conveys the discharge of water closets or similar fixtures to the house drain?

The correct choice is soil pipe, which is specifically designed to carry the discharge from water closets and similar fixtures to the house drain. Soil pipes are constructed to handle waste that contains human excrement and are critical in the sanitary drainage system, ensuring that sewage is transported safely and efficiently away from the fixtures and into the sewer or septic system.

These pipes are usually made from materials that can withstand the corrosive nature of sewage and are sized appropriately to manage the volume of waste flow. The differentiation of soil pipes from other types of drainage pipes, such as waste pipes or drain pipes, lies in their specific function of dealing with solid and liquid waste from toilets.

In contrast, waste pipes typically handle waste from sinks, showers, and other fixtures but do not specifically manage human waste. Drain pipes can encompass a broader range of wastewater conveyance and may not always include the handling of solid waste. Vent pipes, on the other hand, are designed to provide air circulation in the plumbing system to prevent the buildup of pressure and to allow for proper drainage but do not transport wastewater themselves. Understanding these distinctions is essential for proper plumbing installation and compliance with plumbing codes.