There are various grades of both distilled and deionized water. Simple, single distilled water is made in large quantities in many urban areas and is, indeed, cheap. Triple distilled water using tin condensers is used in some chemical and electronic processes and is very expensive. An elaborate deionization and filtration setup can produce water of about the same quality as triple distilled at a somewhat lower cost. A simple deionizing scheme can produce decently pure water at a cost only slightly higher than distillation and at a significantly lower hardware and setup cost. For very small scale water purification, deionization is usually the way to go.
Originally Posted by Photo Engineer