Branch ventilating pipes

Subject to paragraph 2.12 a branch ventilating pipe should be connected to a branch pipe within 300 mm of the trap (see Diagram 2.4) and should be not less than 25 mm diameter or, where the length of the ventilating pipe exceeds 15 m or has more than 5 bends, not less than 32 mm diameter. A branch ventilating pipe should – (a) terminate in the external air at least 900 mm above any opening into a building within 3 m, with a cage or cover which does not restrict the air flow (see Diagram 2.3); (b) connect to a ventilated discharge stack above the "spillover" level of the highest appliance served (see Diagram 2.4); or (c) connect to a ventilating stack (see paragraph 2.13).