At least half of Ohio County remains under a boil water advisory as of Sept. 26, after a main line break at the Perdue Water Plant.
The plant serves about 2500 customers.
The break has been repaired and the system flushed, but water samples are still being tested at the lab.
In the meantime, affected residents are being told to boil their water.
Officials with the Ohio County Water Department say a mechanical failure caused the fluoride to keep running once the water was turned off last week.
Walt Beazley said the fluoride was above normal but never reached a hazardous level.