These AWH non-return valves are engineered for use in pipe lines, systems and machines in the food and drink industry. Suitable for liquid products, additives and cleaning liquids. These valves prevent pipelines running empty and are ideally installed on the pressure side of pumps to prevent the liquid level dropping or higher system components running empty when the pump is switched off. They also are mixing and metering systems combining different medium. Ingeniously, a non-return valve is fitted in every component supply line to prevent penetration of the other components. These valves are characterised by a hygienic, flow-optimised design which facilitates low pressure losses and optimal self-cleaning, and is designed to have an upper and lower section, reliably secured with a clamping connection. The housing is sealed with a U shaped sealing ring, which are totally flush, promoting hygiene. The valve is constructed in accordance with the latest hygiene criteria and equipped with metal stop surfaces to protect the seals. This avoids gaps where germs and product residue can accumulate.