Nitrate removal filter contains a special nitrate-selective resin. Nitrate reduction is 90% to 95% and breakthrough is not affected by sulfate levels. The capacity is 5000 ppm of nitrates as CaCO3. To determine capacity, first calculate the ppm of nitrates as CaCO3, then divide that number into 5000 to get the gallons. This cartridge can be regenerated using sodium chloride brine.