Description Designed to prevent the backsiphonage of contaminated water into the potable water supply. Features a lightweight, durable “disc float” suitable for temperatures up to 180°F (82°C) which closes the atmospheric vent to prevent spilling under all rates of flow. Upon downstream demand, the vent disc assembly rises, sealing the atmospheric vent, allowing water to flow. A loss of supply pressure or the creation of a negative supply pressure causes the vent disc assembly to drop, opening the atmospheric vent and closing the supply side orifice. This prevents backflow by allowing atmospheric pressure to satisfy a vacuum condition on the supply side of the valve. Recommended for low flow installations such as laboratory equipment which use small amounts of water. Contains a durable silicone disc which has high heat and water hammer shock resistance and ensures tight seating with the lightest of seating contacts.