Methods and apparatus for chemical delivery are provided herein. In some embodiments, a first reservoir holds a first volume of fluid, receives a carrier gas, and outputs the carrier gas together with vapor derived from the first volume of fluid. A second reservoir holds a second volume of fluid and is capable of delivering a part of the second volume of fluid to the first reservoir. A self-regulating tube extends from the first reservoir to a region above the second volume of fluid in the second reservoir.