The water usually has an expiration
Don’t buy a regular bottle of regular drinking water or spring water. This water contains more contaminants than you think—not enough to make you sick if you drink it, but you don’t want to add them to the other germs you are working to get out of your sinuses.
Buy some table salt without iodine. Iodine is an irritant to some people. Sea salt is okay, as long as it has the same size grains as table salt.