I work in the public utility sector and APIs is correct. Your public, potable water supply can possibly still have microbes in it even when correctly treated with chlorine and people have contracted fatal microbes using potable water in netty pots. Use distilled water only in netty pots or any other device used to deliver an aqueous solution into the sinus cavities. Deliberately allowing copious amounts of water from your shower head to enter your sinus cavities is a very bad idea.