Hi Tim,

Do you have to replenish the water/oil, or do you just need to add
distilled water to replace what was lost?

When the water evaporates it leaves a brown oil slick on the surface
that really does not mix back in very well so I skim that off. I
usually mix up a fresh gallon and pour it in the tank to make up the
level.

Using distilled water is a bit extreme though??? grin

Dave