Foam Concentrate Pump

A system and method of maintaining a desired additive to water ration in a fire-fighting system including a water flow sensor configured to measure the water flow rate, a water pump, a hydraulic pump, a linear hydraulic cylinder driven by the hydraulic pump, an additive pump mechanically coupled to the linear hydraulic cylinder; and a pump displacement sensor configured to sense the position of the additive pump, the pump displacement sensor being in communication with the water flow sensor to maintain a pre-determined ratio of additive to water.