A dispensing valve cap mountable to a bottle is provided with a first valve part having a tubular portion having an air inlet, the first valve part further including a fluid outlet spaced apart along a longitudinal axis of the tubular portion to form a constant head valve for dispensing fluid from the bottle. A second valve part of the valve movably mounted to the first valve part includes a tubular portion for simultaneously closing both the air inlet and the fluid outlet of the first valve part when fluid dispensing is not desired. The second valve part further includes an air inlet alignable with the air inlet of the tubular portion when fluid dispensing is desired. The dispensing valve cap controls fluid flow from the bottle. The bottle with the valve cap is useable with a dispenser assembly for mixing a concentrated fluid from the bottle with a dilutant. A tamper resistant lock prevents undesired rotation of the second valve part relative to the first valve part. The tamper resistant lock is deactivated upon insertion of the valve cap into the dispenser assembly.