The CITY Series Softeners have a large whole house activated carbon filter in addition to a softener resin tank. This provides not only softened water but the removal of chlorine and ammonia. You have the advantage of luxurious soft water that is free of the obnoxious smell and taste of chlorine. The removal of chlorine also greatly lengthens the life of the softener. High levels of chlorine damages the softener resin and internal rubber seals over time. Since activated carbon has a shorter life than softener resin it must be replaced every 5 to 7 years. This system makes that extremely easy. Merely detach the carbon tank and slide a new one in place.