I still don't quite understand how tap water in a neti-pot is significantly more dangerous than swimming in local lakes, swimming pool or the ocean. Certainly, you get water in your sinuses from that, right?
https://www.allaboutvision.com/contacts/acanthamoeba-keratit...
If you're a contact lens wearer, you should be careful using them while swimming or rinsing them with tap water. A hydrogen peroxide cleaner like Clear Care will help kill amoebas.