can i use bottled natural mineral water instead of distilled as long as i boil it in a microwave as i cant find distilled water while in Korea?

Of course you can use natural mineral water, distilled water or previously boiled water. The reason we mention distilled, previously boiled water or mineral water is because we want to make sure that the water has gone through an adequate filtering and sanitization process. In North America such as the USA and Canada, if the water source is from a government agency, it is considered potable or drinkable water and it is safe to use it for nasal irrigation even though we do not recommend it widely on a precautionary basis.