A plumber is installing a wall-mounted flush valve water closet in a commercial washroom. The rough-in drawing specifies a 290 mm (11.4 in) mounting height from the finished floor to the centreline of the outlet. However, the plumber notices a discrepancy between the architectural drawing and the fixture manufacturer's installation instructions, which indicate a 280 mm (11.0 in) height. What is the most appropriate action for the plumber to take?

Question: A plumber is installing a wall-mounted flush valve water closet in a commercial washroom. The rough-in drawing specifies a 290 mm (11.4 in) mounting height from the finished floor to the centreline of the outlet. However, the plumber notices a discrepancy between the architectural drawing and the fixture manufacturer's installation instructions, which indicate a 280 mm (11.0 in) height. What is the most appropriate action for the plumber to take?

Answer options: ✅ Follow the fixture manufacturer's installation instructions.

• Follow the architectural drawing's specified rough-in height.
• Average the two measurements and set the height at 285 mm.
• Choose the height that appears visually most appealing for the installation.

Correct answer: Follow the fixture manufacturer's installation instructions.

Explanation: Fixture manufacturer's installation instructions always take precedence over architectural drawings for rough-in dimensions, as they ensure proper operation and fit. Following the architectural drawing or averaging the measurements could lead to improper installation or warranty issues.