Easy water distiller - a big spaghetti pot with an angel food cake pan (one that has a hole in the middle) that fits snugly into bigger pot.
Put water in the big pot, start to boil make a dome top out of aluminum foil seal well. Water will make steam, steam will hit foil dome and slowly drip down into the angel food cake pan. Pure H2O.
That takes a lot of energy a Berkey Filter takes none.
Boiling enough water takes a lot of time, work, and fire.
Be careful with distilled water. Because it contains no minerals it will also flush minerals out of your body. A Berkey will allow some of the needed minerals through.
Clever. I will have to buy one.