Abstract: A pasteurized to raw liquid processing system for milk or milk products includes top and bottom tanks, one elevated above the other approximately two feet. The tanks are vented to atmosphere. To prevent foaming, the inlet from a pasteurized source to the top tank is below the liquid level and the same is true of the inlet to the bottom tank which via a throttle valve receives liquid from the bottom of the top tank. Automatic feedback level controls are provided. Since both tanks are vented to atmosphere and because of the gravity flow between the top and bottom tanks, it is impossible to have a vacuum or pressure buildup which would cause a contaminating back flow.