A drinker system for delivering liquid to animals comprising: a central pressure regulator for receiving liquid from a relatively high pressure water source; a plurality of drinker lines, each drinker line having a plurality of drinker nozzles; a plurality of pressure reduction valve devices providing an outlet pressure proportional to the pressure set by the central pressure regulator, the valve devices respectively associated with the plurality of drinker lines and downstream of said central pressure regulator, the valve devices having an inlet fed by piping and an outlet whereat relatively low pressure liquid is provided to the drinker lines; each of the pressure reduction valve devices 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, the relative areas of the diaphragms determining the inlet to outlet pressure ratio of the valve devices; a flow regulating valve through which liquid can flow from the relatively high pressure zone to the relatively low pressure zone when the regulating valve is open; 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, whereby the central pressure regulator can be set to thereby control the outlet pressure of the plurality of drinker lines by affecting the inlet pressure to each of the plurality of pressure reduction valve devices. a central pressure regulator for receiving liquid from a relatively high pressure water source; a plurality of drinker lines, each drinker line having a plurality of drinker nozzles; a plurality of pressure reduction valve devices providing an outlet pressure proportional to the pressure set by the central pressure regulator, the valve devices respectively associated with the plurality of drinker lines and downstream of said central pressure regulator, the valve devices having an inlet fed by piping and an outlet whereat relatively low pressure liquid is provided to the drinker lines; each of the pressure reduction valve devices 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, the relative areas of the diaphragms determining the inlet to outlet pressure ratio of the valve devices; a flow regulating valve through which liquid can flow from the relatively high pressure zone to the relatively low pressure zone when the regulating valve is open; 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, whereby the central pressure regulator can be set to thereby control the outlet pressure of the plurality of drinker lines by affecting the inlet pressure to each of the plurality of pressure reduction valve devices. 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, the relative areas of the diaphragms determining the inlet to outlet pressure ratio of the valve devices; a flow regulating valve through which liquid can flow from the relatively high pressure zone to the relatively low pressure zone when the regulating valve is open; 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, whereby the central pressure regulator can be set to thereby control the outlet pressure of the plurality of drinker lines by affecting the inlet pressure to each of the plurality of pressure reduction valve devices.