Hi, I have a couple of issues 1) Need a manual. 2) Trying to clean nozzle and venturi the cap will not come off. I think It should screw off but it appears to be stuck and I do not want to break the softner. Any tips. 3) Also how much iron content can the softener handle. 4)what is the shelf life of ths softerner. Any assistance is greatly appreciated. All of a sudden everthing is turning yellow.