distilliation is an easy enough process.

Boil water, have some way of catching the vapor, and have it go into a clean container. Ideally, you'd have some kind of coolant (fresh water, etc) running around the tube so the vapor condenses.

They make distillers pretty cheaply (a glass tube with a larger tube outside for a continuous supply of cold water), but I'd imagine you could use a pyrex or corningware pot on the stove along with a lid and a hose (inert plastic or glass piping) going to another pot off the heat.