Technical Booklet N Drainage·Page 12·2.6
Ventilation
To prevent water seals from being broken by system pressures, branch pipes must be ventilated according to paragraph 2.11 or constructed as described in paragraph 2.12.
To prevent the water seal from being broken by the pressures which may develop in the system a branch pipe should either be ventilated as described in paragraph 2.11 or constructed as described in paragraph 2.12.
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