Granular Activated Carbon, or GAC, is another method to remove VOC's (Volatile Organic Contaminants). Carbon is placed inside a pressurized vessel and as water runs through it, the organic material is trapped within the pores of the carbon. Once the carbon has been completely saturated or used up, it is replaced with new activated carbon. We test the water throughout the vessel to ensure its operation and also to let us know when the carbon needs to be replaced before it becomes 100% saturated.