Abstract: Provided is a tank including a polymeric upper dome having a neck with a through passage, a polymeric lower dome having a neck with a through passage, a polymeric shell having a first end connected to the upper dome and a second end connected to the lower dome, and a connection attached to each of the upper and lower domes in the through passages of the necks, wherein the upper dome, lower dome, and shell form a cavity. The tank includes at least one stop feature to prevent overtightening of an attachment to the tank, at least one feature to prevent loosening of the attachment from the tank, and a feature to prevent a diaphragm from sticking to the inside of the tank walls.