In January, Mary Wade, who lives with her husband and two dogs in a modest row house on Seventh Street NW, got a water bill for $12,418.21.

She went to the city's water department and complained. Her previous bills averaged about $28. City officials told her they would check on it.

Last week, Mary Wade got a new water bill, this one for $14,985.90.

"I'm not paying it," said Wade. "I went down there in January and they told me don't worry we're going to straighten it out. A man came out here to read the meter but it didn't mean nothing. They just went ahead and now they've sent me this bill. . .

"I hope they do come out here and turn off my water," Wade said as she stood on the sidewalk in front of her home with D.C. Council member John Ray, a candidate for mayor, and several reporters Ray brought along to show why he says the city government needs new leadership.

"I'll take them to court and teach those folks downtown how to stop drinking coffee, wasting time and telling lies when you go down there to find out what's wrong," Wade fumed.

City officials later admitted Wade's bill was in error and promised to send a correct bill for $98. Mayor Marion Barry called her to apologize.

And, at a hastily called sidewalk news conference outside the water billing headquarters, D.C. Environmental Services Director William B. Johnson insisted that the incorrect bill was "an isolated case," not an indication that Barry has failed to solve the city's nagging problems with water bills.

In his campaign for reelection, Barry has made a point of saying that his administration is just around the corner from clearing up the water bill problem. But that has not stopped many of his opponents in the Sept. 14 Democratic primary from regularly pointing to water bills and claiming them as proof that Barry's administration is inept.

After leaving Wade's house in the middle-income Petworth neighborhood yesterday, candidate Ray told reporters that he thought Barry should "clean house" at DES, replacing Johnson, Enrique Jograj, the head of the water billing operations, and several unnamed assistants. He also called on Barry to impose a moratorium on sending out six-month bills of more than $200 for any single family residence.

City officials acknowledged yesterday that they knew of problems with Wade's bills as early as last October, when a bill for $11,322 was printed by their computer but not sent to Wade. They said the computer is programmed to alert them to any residential bill over $400.

But they were unable to explain why the bill was not corrected then or in January, when Wade went to their offices at 613 G St. NW to complain at the invitation of Jograj, who spoke with her on a radio call-in show.

Johnson maintained at yesterday's press conference that his department has an error rate of "less than one percent" for the approximately 125,000 residential and commercial billing accounts.

He said the employe responsible for reading Wade's meter and others in that neighborhood was fired last month for poor job performance. Johnson declined to name the person.

He said four other meter readers have been fired over the last year. The city now has 13 meter readers and plans to hire five replacements.

"We made an honest effort (in Wade's case)," Johnson told reporters. "We don't need for it to be given the kind of attention it is getting . . . We have a high degree of confidence that we are reading bills accurately. There are going to be some problems of human error. We're talking about a rotten system of a couple years ago."

City officials say they receive an average of about 650 calls a week about water bills, but were unable to say how many of those calls are complaints.

Ray came to Wade's house after learning of her problem with her water bill from one of her neighbors. As Ray was leaving the house, a reporter asked Wade her choice for mayor in the fall elections.

"I'm going to vote for Pat Harris," Wade responded. "She knows how to solve these administrative problems that these folks don't know how to handle."