Technical Booklet N Drainage·Page 16·2.13(b)
Ventilation stack termination - air admittance valve
The upper end of a ventilation stack may terminate with an air admittance valve complying with BS EN 12056: Part 2 and BS EN 12380.
The upper end of a ventilation stack should terminate with an air admittance valve which complies with BS EN 12056: Part 2 and BS EN 12380.
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