“Naegleria fowleri infects people when water containing the ameba enters the body through the nose. Infection is rare and typically occurs when people go swimming or diving in warm freshwater places, like lakes and rivers. Very rarely, infections have been reported when people submerge their heads, cleanse their noses during religious practices, or irrigate their sinuses (nose) using contaminated tap or faucet water. Naegleria fowleri can grow in pipes, hot water heaters, and water systems, including treated public drinking water systems. You cannot get infected from drinking water contaminated with Naegleria. You can only be infected when contaminated water goes up into your nose.”
https://www.cdc.gov/parasites/naegleria/prevention.html
A lot of people do that sinus washing where they carefully pour water up their nose to slosh around in the nasal sinuses and are drained. I believe there were a few cases in u.s. when the water used was contaminated with the amoeba.
I would rather drink lots of water(if it would be ok, considering any condition I have) to dilute sinus secretions, rather than risk putting some bad stuff up my nose.