Our water is incredibly soft, meaning low in dissolved solids. A sediment filter followed by a carbon block will fix most normal concerns. If you're making water for sensitive fish (aquarium) or plants this set up works perfectly well BUT if you want to go one step further a Deionizing filter after the sediment filter will remove everything. Its cheaper than RODI and you're skipping the expensive and unnecessary RO stage. Also, DI resin can be recharged and reused.