What ever water you use to drink is fine, 20 minutes would be plenty long.
All ozanators will work for this purpose.
There are many uses for ozone, some people have went to jail for selling them for cancer, etc. I sell them for cleansing. If you have a large one they are great to cleanse the house of mould/oders, etc. I only sell the small models that are used for the mop up program, etc.