A liquid sprayer apparatus, comprising: a liquid container having an opening; a spray mechanism sealingly engageable to said liquid container adjacent said opening to fluidically communicate with an interior of said liquid container, said spray mechanism including: (i) a monolithic main body defining a first channel with a first channel wall and a second channel with a second channel wall fluidically connected to each other through a first passage; (ii) a charge piston coordinating with said first channel wall to define a collection chamber, said charge piston defining a third channel through which liquid may be introduced to said collection chamber; (iii) a one-way inlet valve permitting liquid flow from said third channel to said collection chamber, wherein said third channel is separated from said collection chamber by said one-way inlet valve; (iv) a dispensation piston and a discharge valve base contacting with said second channel wall to define a dispensation chamber, said dispensation piston being responsive to a fluid pressure in said dispensation chamber against a second restorative force; (v) a one-way outlet valve permitting liquid flow from said collection chamber to said dispensation chamber through said first passage; (vi) an actuator for selectively moving said charge piston with respect to said first channel wall against a first restorative force to reduce a collection chamber volume of said collection chamber; and (vii) a one-way discharge valve for permitting liquid flow from said dispensation chamber through a second passage in said discharge valve base, wherein said discharge valve opens when the fluid pressure in said dispensation chamber exceeds a first threshold pressure. a liquid container having an opening; a spray mechanism sealingly engageable to said liquid container adjacent said opening to fluidically communicate with an interior of said liquid container, said spray mechanism including: (i) a monolithic main body defining a first channel with a first channel wall and a second channel with a second channel wall fluidically connected to each other through a first passage; (ii) a charge piston coordinating with said first channel wall to define a collection chamber, said charge piston defining a third channel through which liquid may be introduced to said collection chamber; (iii) a one-way inlet valve permitting liquid flow from said third channel to said collection chamber, wherein said third channel is separated from said collection chamber by said one-way inlet valve; (iv) a dispensation piston and a discharge valve base contacting with said second channel wall to define a dispensation chamber, said dispensation piston being responsive to a fluid pressure in said dispensation chamber against a second restorative force; (v) a one-way outlet valve permitting liquid flow from said collection chamber to said dispensation chamber through said first passage; (vi) an actuator for selectively moving said charge piston with respect to said first channel wall against a first restorative force to reduce a collection chamber volume of said collection chamber; and (vii) a one-way discharge valve for permitting liquid flow from said dispensation chamber through a second passage in said discharge valve base, wherein said discharge valve opens when the fluid pressure in said dispensation chamber exceeds a first threshold pressure. (i) a monolithic main body defining a first channel with a first channel wall and a second channel with a second channel wall fluidically connected to each other through a first passage; (ii) a charge piston coordinating with said first channel wall to define a collection chamber, said charge piston defining a third channel through which liquid may be introduced to said collection chamber; (iii) a one-way inlet valve permitting liquid flow from said third channel to said collection chamber, wherein said third channel is separated from said collection chamber by said one-way inlet valve; (iv) a dispensation piston and a discharge valve base contacting with said second channel wall to define a dispensation chamber, said dispensation piston being responsive to a fluid pressure in said dispensation chamber against a second restorative force; (v) a one-way outlet valve permitting liquid flow from said collection chamber to said dispensation chamber through said first passage; (vi) an actuator for selectively moving said charge piston with respect to said first channel wall against a first restorative force to reduce a collection chamber volume of said collection chamber; and (vii) a one-way discharge valve for permitting liquid flow from said dispensation chamber through a second passage in said discharge valve base, wherein said discharge valve opens when the fluid pressure in said dispensation chamber exceeds a first threshold pressure.