A vapor delivery system includes an ampoule to store liquid precursor and a heater to partially vaporize the liquid precursor. A first valve communicates with a push gas source and the ampoule. A second valve supplies vaporized precursor to a heated injection manifold. A valve manifold includes a first node in fluid communication with an outlet of the heated injection manifold, a third valve having an inlet in fluid communication with the first node and an outlet in fluid communication with vacuum, a fourth valve having an inlet in fluid communication with the first node and an outlet in fluid communication with a second node, a fifth valve having an outlet in fluid communication with the second node, and a sixth valve having an outlet in fluid communication with the second node. A gas distribution device is in fluid communication with the second node.