EPDM Special SIPHON Outlet

Wallbarn has an ingenious product designed to improve the environment around drainage holes on roofs and podium decks. These products specifically target any unwanted smells, and are particularly useful on terraces or balconies, where greater pedestrian presence is anticipated, where the deck is used for dining, for example.
http://www.wallbarn.com/products/roof-outlets-vents/roof-outlets-collars/epdm/epdm-special-siphon-outlet/