Which water supply size is required for a flushometer-type water closet (W/C)?

A flushometer-type water closet requires a water supply size of 1 inch. This larger diameter is necessary because flushometer valves operate by rapidly discharging a significant volume of water to efficiently clear waste from the toilet bowl. The 1-inch supply line provides adequate water pressure and flow rate, ensuring that the flushometer can operate effectively and deliver a powerful enough flush to maintain proper sanitation and functionality.

The other sizes listed – 1/4", 1/2", and 3/4" – do not provide sufficient water flow for a flushometer mechanism. Smaller diameters would restrict the water supply, resulting in lower pressure and inadequate flushing performance. Thus, the standard requirement for effective and efficient operation of flushometer-type water closets is indeed a 1-inch water supply line.