The Denver Post reports the letters were sent Monday, and residents who have had a softener installed can get a free inspection if they are worried about potential contamination.
City spokeswoman Michelle Halstead has said California-based Aquakleen Products Inc. notified the city in September, and the city gave the company 30 days to fix any problems. Court records show Aquakleen was ordered to pay more than $900,000 to a couple who drank tainted water. Their home's clean water system was connected to their sewage line, which backed up into their drinking water system.
The Post reports a representative from Aquakleen was unavailable for comment Monday.
(Copyright 2012 by The Associated Press. All Rights Reserved.)