I have a 3 year old 450 gal. hot tub. Will converting it to a salt waters system harm any parts of the tub or void the warranty? Also will the salt water help with eczema ?Are the nature 2 cartridges still helpful ?

Hello Mike, saltwater systems are very popular but you would need to ask your hot tub manufacturer if adding one would affect the warranty. A doctor should advise you if it would be beneficial for eczema. The nature 2 cartridges would be fine, but unnecessary with one of the saltwater systems. I would advice that you consider the TechniChlor or the ChlorMaker DO for a hot tub that large. The larger models will work more efficiently and will likely last longer.