During 2011, two people in Louisiana died of brain infections after using unboiled tap water instead of sterile water in their neti pots.

Announcing the deaths (from the amoeba-borne infection, Naegleria fowleri), the local health department said that while tap water is safe to drink, it's not safe for irrigating nasal passages. “Use distilled, sterile or previously boiled water [for] the irrigation solution,” the warning said. It's also wise to clean neti pots regularly with an antibacterial soap and always let them air dry thoroughly.