Technical Booklet N Drainage·Page 12·2.3
Water seals (traps)
All discharge points into a drainage system must be fitted with a water seal (trap) to prevent system air from entering the building. Minimum trap sizes and seal depths are specified by appliance type.
All points of discharge into a system should be fitted with a water seal (trap) to prevent air from the system entering the building. The minimum size of trap and depth of seal for an appliance should be as given in Table 2.3.
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