An endoscopic valve (200; 300), comprising: a valve stem (220; 320), comprising: a proximal channel with a proximal opening and a distal channel with a distal opening, the proximal and distal channels defining a contiguous channel, a first port formed within a sidewall of the valve stem and in fluid communication with the proximal channel, and a second port formed within the sidewall of the valve stem and in fluid communication with the proximal channel; a first seal disposed around an outer surface of the valve stem and distal to the first port; a second seal disposed around the outer surface of the valve stem and distal to the second port; a third seal disposed around the outer surface of the valve stem and distal to the second seal; a gating member slidably disposed within the proximal channel, wherein the gating member is configured to move between a first position in sealing contact with the first port and a second position in sealing contact with the second port, and wherein a lumen extends through the gating member; and a valve insert disposed between the proximal and distal channels (224, 230); and a housing removably attachable to an endoscope handle, wherein the valve stem is movable between a first configuration and a second configuration within the housing, the housing comprising: an air outlet port formed within a sidewall of the housing; an air inlet port formed within the sidewall of the housing and distal to the air outlet port; a water outlet port formed within the sidewall of the housing and distal to the air inlet port; and a water inlet port formed within the sidewall of the housing and distal to the water outlet port. a valve stem (220; 320), comprising: a proximal channel with a proximal opening and a distal channel with a distal opening, the proximal and distal channels defining a contiguous channel, a first port formed within a sidewall of the valve stem and in fluid communication with the proximal channel, and a second port formed within the sidewall of the valve stem and in fluid communication with the proximal channel; a proximal channel with a proximal opening and a distal channel with a distal opening, the proximal and distal channels defining a contiguous channel, a first port formed within a sidewall of the valve stem and in fluid communication with the proximal channel, and a second port formed within the sidewall of the valve stem and in fluid communication with the proximal channel; a first seal disposed around an outer surface of the valve stem and distal to the first port; a second seal disposed around the outer surface of the valve stem and distal to the second port; a third seal disposed around the outer surface of the valve stem and distal to the second seal; a gating member slidably disposed within the proximal channel, wherein the gating member is configured to move between a first position in sealing contact with the first port and a second position in sealing contact with the second port, and wherein a lumen extends through the gating member; and a valve insert disposed between the proximal and distal channels (224, 230); and a housing removably attachable to an endoscope handle, wherein the valve stem is movable between a first configuration and a second configuration within the housing, the housing comprising: an air outlet port formed within a sidewall of the housing; an air inlet port formed within the sidewall of the housing and distal to the air outlet port; a water outlet port formed within the sidewall of the housing and distal to the air inlet port; and a water inlet port formed within the sidewall of the housing and distal to the water outlet port. an air outlet port formed within a sidewall of the housing; an air inlet port formed within the sidewall of the housing and distal to the air outlet port; a water outlet port formed within the sidewall of the housing and distal to the air inlet port; and a water inlet port formed within the sidewall of the housing and distal to the water outlet port.