What is the minimum capacity of the water tank needed for a complete water closet flushing in a toilet?

In determining the minimum capacity of the water tank required for a complete water closet flushing in a toilet, the correct answer highlights that 12 liters is sufficient. Most modern toilets are designed to use approximately 6 to 9 liters per flush for efficiency, especially in low-flow models. However, it is important to ensure that the tank can reliably deliver enough water to clear waste effectively. The choice of 12 liters typically allows for ample capacity to achieve a proper flush while still being aligned with water conservation efforts.

Options suggesting larger capacities like 15 liters, 19 liters, and 26 liters might represent more traditional or less efficient flushing systems, but they are not necessary for adequate functionality in modern standards. The 12-liter tank meets the minimum requirement while balancing efficiency with the ability to perform an effective flush. Therefore, it adequately addresses the needs of contemporary sanitation design, focusing on minimizing water usage without compromising performance.