Patent ID: 8006324

Claim:
A method of constraining gas within an effluent discharge pipe of a urinal comprising discharging an allotment of collapsible foam comprising gas bubbles within a fluid inside the discharge pipe to form a replaceable, collapsible foam plug entirely across a passageway through the discharge pipe which foam plug is stable for a period of time, the method including providing a support for the foam in the discharge pipe, discharging the foam into the passageway of the discharge pipe above the support so that the foam engages the support, and providing as the support a lower screen member disposed across the passageway and an upper screen member disposed across the passageway, the method including discharging the foam into the discharge pipe intermediate the lower screen member and the upper screen member in a manner that the foam entirely fills a cavity defined within the passageway through the discharge pipe between the upper screen member and the lower screen member, including discharging sufficient foam that the foam fills the cavity engaging each of the upper screen member and the lower screen member.