A drinker system for delivering water to animals comprising: a central pressure regulator； drinker lines with drinker nozzles； pressure reduction valve devices providing an outlet pressure proportional to the pressure set by the central pressure regulator； each valve device comprising: a housing defining a relatively high pressure zone and a relatively low pressure zone； a relatively small area diaphragm in the relatively high pressure zone； a relatively large area diaphragm in the relatively low pressure zone, and rigidly connected to the small area diaphragm； a flow regulating valve through which liquid can flow from the relatively high pressure zone to the relatively low pressure zone； and an internal by-pass mechanism for allowing liquid to flow from the valve device inlet to the valve device outlet bypassing the flow regulating valve.
