Stop freaking out. Tap water is the safest water you can drink for that purpose, whatever it is you're talking about there with amoebas. The main thing about a Netty pot is to use salt water, and the type of salt might be important. Unless there is an alert in your area you don't have to boil tap water. You boil water when an alert has been issued, whether it's well water, spring water, or tap water, because it's gotten contaminated. That's why they put all that chlorine in tap water. Now, whether it's truly safe to drink or not is a different story, but in this case, you're worrying over nothing. Brain eating amoebas?
Oh my goodness. I am thinking that it is highly unlikely your water is contaminated with brain eating amoebas. My husband uses tap water unboiled frequently with his neti pot for a chronic sinus issue. His brain is intact. (I think . . ha ha). Do you suffer this type of anxiety and over the top, catastrophic thinking frequently?