Two more astronomically inaccurate residential water bills came floating out of the District Building yesterday, just as Mayor Marion Barry was pressing city bureaucrats to explain a $14,985 bill disclosed by one of Barry's political opponents at a press conference the day before.

Council member John Ray, who is running against Barry in the Sept. 14 Democratic primary, followed his $14,000 disclosure of Thursday by revealing the case of Robert Silverburg of 47th Street NW, whose water bill for a 52-day period during December and January was $11,273.36 plus a late payment penalty of 10 percent.

And council member Betty Ann Kane, who also is challenging Barry in this fall's Democratic primary, weighed in with the case of Salvador Motsuk of Queens Chapel Terrace NE, whose most recent water bill was $12,494.49.

"I received it on April 1. My wife was laughing that it was an April Fool's joke," said Motsuk, a civilian employe of the Navy. "I wasn't laughing."

Motsuk said he's been told by water officials "not to worry," that his water will not be cut off. "But these are the same people who told me I owed" the large bill, Motsuk said.

Although Motsuk is still waiting to find out what his bill should be, water officials who were asked about Silverburg said his actual bill should be $38.66.

Barry huddled with top officials of the water billing bureau yesterday and later told reporters, "I am appalled and outraged at any water bill that's not accurate."

Barry said he gave the officials, including William B. Johnson, environmental services director, a "pep talk," but he declined to discuss the meeting.

Meanwhile yesterday, the D.C. auditor, who works for the City Council, released a 15-page report that accused city water officials of not doing enough to solve longstanding water billing problems.

The report by Auditor Otis H. Troupe praised the department for cutting from 10 days to three the time it takes to credit most payments to customers. But, it said, even the three-day period allows for thousands of dollars in erroneous late charges to be made against customers who pay near their cutoff deadlines.

The audit did not address the department's excessive billing problem, but revealed that in March there was a backlog of 3,700 water bill payments that were processed late by the First American Bank, which has a contract with the city.

The report said the city should recheck all of those bills to determine whether incorrect late charges were assessed and also recommended that the department "undertake prompt development of the special computer program to deal with erroneous late charges."

Enrigue Jograj, head of the water billing division, said yesterday that the department has made major inroads in correcting the problems. "We just have to get our people to follow the procedures," he said.

The city's nagging problems with water bills was highlighted Thursday when Ray summoned reporters to the home of Mary Wade, who lives in a modest row house on Seventh Street NW with her husband and two dogs.

Wade recounted the problems that began last week when she received a six-month bill for $14,985.90 that was reduced to $98 after the press conference Thursday.

Johnson called hers "an isolated case" that did not reflect the error rate of less than 1 percent in his department's handling of claims for the city's 125,000 water accounts.

While city officials were sorting out the bureaucratic developments, the candidates for mayor were competing to claim Wade's support, which on Thursday she said would go to Patricia Roberts Harris.

Ray called Wade at her home yesterday morning, and then, on the subject of voting for Harris, told a reporter, "She says she didn't say that."

And Kane, who called a reporter to say Wade was not saying for whom she would vote, let it be known that her office had been working on Wade's problem for a couple of days. "John Ray was not working on it," Kane contended, "he just publicized it."