A pull pump (210; 410; 610; 830; 930) comprising: a housing (250; 450; 650; 832; 932); a piston (220; 420; 620; 840; 940) that reciprocates within the housing (250; 450; 650; 832; 932), the piston (220; 420; 620; 840; 940) having an outer wall and at least a portion of the center of the piston (220; 420; 620; 840; 940) is hollow, and the piston (220; 420; 620; 840; 940) including an orifice (230; 430; 630; 846; 946) from the outer wall to the center of the piston (220; 420; 620; 840; 940); a first seal (228; 428; 628; 845; 945) located proximate the upper end of the piston (220; 420; 620; 840; 940) to provide a seal between the piston (220; 420; 620; 840; 940) and the housing (250; 450; 650; 832; 932), the first seal (228; 428; 628; 845; 945) being located above the orifice (230; 430; 630; 846; 946) in the piston wall; a liquid inlet (280; 480; 680; 834; 934); a one-way liquid inlet valve (282; 482; 682; 850; 950); a liquid outlet; a charge chamber (285; 477; 632; 847; 947); and a mixing chamber (274; 474; 674); wherein the charge chamber (285; 477; 632; 847; 947) is dispensed by pulling the piston (220; 420; 620; 840; 940) downward and recharged by moving the piston (220; 420; 620; 840; 940) upward, characterized in that: the liquid outlet has a one-way liquid outlet valve (233, 234; 434; 675, 676; 842; 942); the charge chamber (285; 477; 632; 847; 947) is defined at least in part by the one-way liquid inlet valve (282; 482; 682; 850; 950), the one-way liquid outlet valve (233, 234; 434; 675, 676; 842; 942), a wall of the housing (250; 450; 650; 832; 932) and a wall of the piston (220; 420; 620; 840; 940); the mixing chamber (274; 474; 674) is located downstream of the one-way liquid outlet valve (233, 234; 434; 675, 676; 842; 942); and the liquid inlet (280; 480; 680; 834; 934) is located in the side wall of the housing (250; 450; 650; 832; 932) at a point lower than the top of the piston (220; 420; 620; 840; 940). a housing (250; 450; 650; 832; 932); a piston (220; 420; 620; 840; 940) that reciprocates within the housing (250; 450; 650; 832; 932), the piston (220; 420; 620; 840; 940) having an outer wall and at least a portion of the center of the piston (220; 420; 620; 840; 940) is hollow, and the piston (220; 420; 620; 840; 940) including an orifice (230; 430; 630; 846; 946) from the outer wall to the center of the piston (220; 420; 620; 840; 940); a first seal (228; 428; 628; 845; 945) located proximate the upper end of the piston (220; 420; 620; 840; 940) to provide a seal between the piston (220; 420; 620; 840; 940) and the housing (250; 450; 650; 832; 932), the first seal (228; 428; 628; 845; 945) being located above the orifice (230; 430; 630; 846; 946) in the piston wall; a liquid inlet (280; 480; 680; 834; 934); a one-way liquid inlet valve (282; 482; 682; 850; 950); a liquid outlet; a charge chamber (285; 477; 632; 847; 947); and a mixing chamber (274; 474; 674); wherein the charge chamber (285; 477; 632; 847; 947) is dispensed by pulling the piston (220; 420; 620; 840; 940) downward and recharged by moving the piston (220; 420; 620; 840; 940) upward, characterized in that: the liquid outlet has a one-way liquid outlet valve (233, 234; 434; 675, 676; 842; 942); the charge chamber (285; 477; 632; 847; 947) is defined at least in part by the one-way liquid inlet valve (282; 482; 682; 850; 950), the one-way liquid outlet valve (233, 234; 434; 675, 676; 842; 942), a wall of the housing (250; 450; 650; 832; 932) and a wall of the piston (220; 420; 620; 840; 940); the mixing chamber (274; 474; 674) is located downstream of the one-way liquid outlet valve (233, 234; 434; 675, 676; 842; 942); and the liquid inlet (280; 480; 680; 834; 934) is located in the side wall of the housing (250; 450; 650; 832; 932) at a point lower than the top of the piston (220; 420; 620; 840; 940). the liquid outlet has a one-way liquid outlet valve (233, 234; 434; 675, 676; 842; 942); the charge chamber (285; 477; 632; 847; 947) is defined at least in part by the one-way liquid inlet valve (282; 482; 682; 850; 950), the one-way liquid outlet valve (233, 234; 434; 675, 676; 842; 942), a wall of the housing (250; 450; 650; 832; 932) and a wall of the piston (220; 420; 620; 840; 940); the mixing chamber (274; 474; 674) is located downstream of the one-way liquid outlet valve (233, 234; 434; 675, 676; 842; 942); and the liquid inlet (280; 480; 680; 834; 934) is located in the side wall of the housing (250; 450; 650; 832; 932) at a point lower than the top of the piston (220; 420; 620; 840; 940).