Adam Simpson, Chief Operator for the Wilmington Water Department, checks the chemical feed pump on Thursday morning when the city began adding fluoride to the drinking water. It’ll take about three days for the fluoridated water to reach all customers, according to the Water Department. Operators at the water treatment plant have been certified by Ohio EPA to conduct fluoride tests on the water, with tests to be completed every few hours to ensure the proper fluoride level is in the water. Other equipment was also installed at the plant to help operators monitor for a consistent fluoride feed.