impeller the magnet or magnets 88 operate to communicate with a reed switch that is a component of the electronic 39 s assembly 72 to count or track each time the magnet s pass over the reed switch this allows the filter unit 10 to determine how much the volume of water water follows through the filter unit 10 when the volume of water following through the filter unit 10 surpasses or is approximately the maximum volume capable of being effectively treated by the filter media portion 20 typically a sufficient charge has accumulated in a capacitor 90 of the electronic assembly such that the solenoid is activated or the solenoid itself is activated without the use of a capacitor and the retaining member 84 is retracted by the solenoid once the retaining member has been retracted the water impeding object 82 spherical member is allowed to flow along with the water flow flowing through the water impeding valve and moves into engagement with an internal bottleneck portion 92 of the typically hourglass shaped water impeding valve as a result the water flowing through the filter unit 10 is slowed or stopped typically water is allowed to flow through at an approximately 75 to 80 reduced rate from the water flow rate prior to activation of a solenoid and the retracting of the retaining member 84 the impeller 60 typically has a plurality of water engaging fins 94 that radially extend away from a central hub 96 the water engaging.