The City of Bloomington's monthly test results for levels of disinfectant byproducts showed a rise, but they remain within the allowable limits.
The city announced increased levels of the contaminants in January 2016, then launched an effort to reduce the levels.
And although the city doesn't directly point to a change in the way the water is disinfected as a cause for the rise in DBPs, Utilities Director Vic Kelson says the CBU began pre-chlorinating the water again for the first time since April 2016.
"This was necessary because disinfection of colder water requires more contact time with the chlorine disinfectant," Kelson said in a statement.
Kelson says the city will stop pre-chlorinating the water when the water warms up in the spring.
Disinfectant byproduct levels are lower on average than they were at this time last year.