NO NO NO NO many times NO SALT..BAD idea!
In fact, it will not even work if you use salt. You MUST use the purest distilled water [look for sodium free on the label as well..but most distilled water is sodium free anyway] or the PPM/voltage reference circuitry will detect contaminants such as minerals [including salt] as silver and shut itself down.

Well water, spring water, reverse osmosis water, charcoal filtered water, city water, no matter how well filtered, probably won't work at all.

Home distilled water is touchy. Everything must be absolutely clean and the water cannot be run through charcoal afterwards. [Some steam distillers do that to enhance flavor] Double distill and don't let the distiller run dry. If it has a slow setting, use it.

Most distilled water is 'ozonated', hence, there is bound to be a great deal of dissolved oxygen in the water. This oxygen can combine with pure silver ions , producing excessive silver oxides and can sometimes turn the colloidal silver suspension yellow. Even using 'regular' distilled water yields better results if it has been stored loosely capped for a while or preheated and cooled to room temp [or at least under 110deg f]. This allows dissolved oxygen to escape.
The only legitimate way to increase the initial conductivity of the water to decrease the run time is to 'seed' it with a little colloidal silver from a previous run.