Backflow valve

Abstract

A backflow valve for use in a post-mix carbonator system for preventing the backflow of carbonated fluid, thereby preventing the contamination of the fresh water supply, and indicating when such a backflow condition exists or has occurred. The backflow valve comprises a check seat body which houses an elastomeric valve member, and a sight glass body for viewing the position of the elastomeric valve member. The backflow valve also comprises top and base connectors for connecting the backflow valve to the fluid carrying line and a shut-off/flush valve for controlling the flow of fluid through the device. The elastomeric valve member allows the flow of fluid from the supply to the outlet when the fluid pressure at the supply exceeds the pressure at the outlet and prevents the reverse flow of fluid when the pressure at the outlet exceeds the pressure at the supply. As the pressure at the outlet increases, the elastomeric valve member is forced in the upstream direction over a plurality of steps in the check seat body. As the elastomeric valve member passes over each step, it engages the step and is thereby prevented from returning to its original viewed downstream position. The position of the elastomeric valve member may be through the sight glass body which has a line demarking the normal position of the elastomeric valve member.