City auditors are investigating billing problems at the city’s water department. Water officials have already acknowledged the city overcharged several hundred customers an average of $300 apiece. The mess has put unwanted attention on a major plan to change the way the city collects information from water users. If it were up to the city water department, auditors would definitely not look into the $60 million effort to install 280,000 new “smart meters” across the city – at least not right now.