ATLANTA (AP/WAOK) - An audit commissioned by Atlanta has revealed that thousands of city water customers had defective meters that could have caused them to pay too much or too little for several years.

Preliminary audit results obtained show that about 6 percent of 158,000 residential meters inspected had defects that could affect bills.

City officials say fewer than half of those customers were overcharged. City staffers must still calculate the amounts of discrepancies and determine refunds or credits to customers.

The audit comes five years after the start of a $35 million project to install automated meter reading throughout Atlanta’s water system. That project was supposed to improve billing accuracy, identify potential leaks and cut the time it takes to read meters.