"We just finished a total upgrade of our water billing system in the last two years; we do not use the same system Baltimore uses," county spokesman Kevin Enright wrote in an email. He said the error rates are now at 1 percent.
In 2009, the county started an eight-year initiative to replace older transmitters with more reliable units, according to the county's website.
Baltimore City officials said a nearly 40-year-old meter-reading system was a contributing factor after 38,000 households in the city and Baltimore County were found in a recently released audit to have been overbilled.
The audit evaluated 70,000 households over the past three years and found that 65,000 were likely overcharged. That system serves 400,000 customers in Baltimore and Baltimore County.
Howard County gets its water from Baltimore's Liberty Reservoir. The water is treated at the Ashburton water filtration plant, according to the city's public works website. Through three connections, Howard receives an average flow of 38.5 million gallons of water a day, with a maximum of 68.1 million gallons a day.