Abstract: An assembly for dispensing a constant flow of liquid from a bottle independent of the level of liquid in the bottle. The assembly has a two-part cap with an inner portion and an outer portion. The inner portion is affixed to the bottle and has a generally cylindrical air chamber which extends into the liquid in the bottle. This inner cap member has an opening in the bottom. An outer cap member has a mating air chamber and a mating opening in the bottom. When the outer cap member is turned with respect to the inner cap member to a closed position, no liquid can pass through the misaligned openings. There are also a set of alignable air openings in the air chambers of the inner and outer cap members which permit air to exit from the air chamber into the liquid when the liquid outlet openings are aligned. The result is a constant flow rate out of the bottle no matter what the height of liquid in the bottle may be until the bottle is essentially empty.