An additive system is used with a post mix dispensing machine having a liquid inlet, and a supply of an additive for mixing with the liquid from the liquid inlet. A pump, having an additive inlet and an additive outlet, is coupled to a source of power. An additive supply line is coupled to the additive inlet. The additive supply line is coupleable to a source of an additive. A liquid delivery line connects the liquid inlet to a mixture delivery outlet. An additive delivery line connects the additive outlet to a mixing point along the liquid delivery line. An additive flow adjuster is used to control the flow of additive from the pump. Additive flowing through the additive delivery line mixes with liquid flowing through the liquid delivery line for passage to the mixture delivery outlet.