Technical Booklet N Drainage·Page 12·2.4
Watertightness
The drainage system must withstand air or smoke testing at positive pressure of 38 mm water gauge for at least 3 minutes, with all traps maintaining a minimum 25 mm water seal.
The system should be capable of withstanding an air or smoke test of a positive pressure of 38 mm on a water gauge for at least 3 minutes, and every trap should maintain a water seal of at least 25 mm.
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