Health officials announced the update Friday for the city north of Grand Rapids.
Officials had advised residents to use bottled water Wednesday or boil tap water before using it for drinking, brushing teeth or preparing food.
The Kent County Health Department said there were equipment problems at the Rockford water plant over the Labor Day holiday weekend. Rockford has approximately 5,800 residents and draws its water from wells.
There have been no reports of illness, although E. coli can cause severe cramps, nausea and diarrhea.