If General Services Administrator Gerald P. Carmen approves, GSA personnel will be out painting the Pentagon, fixing the roof of a Health and Human Services Department auditorium and repairing leaky downspouts at the Agriculture Department within weeks after President Reagan signs the jobs bill into law.

These projects, to be financed by $125 million in the legislation moving through Congress, are among 851 federal building repairs that the GSA has tentatively put on a "fast track" in anticipation of the bill's passage. Carmen estimates that the projects would create about 5,000 new jobs nationwide during the next six months.

The Senate passed its version of the jobs bill yesterday. A conference committee must resolve differences between the House and Senate bills. However, both measures contain $125 million for federal repair work.

Officials in GSA's Public Buildings Service have spent several weeks screening the repair work scheduled over the next six years and selecting critical projects. Most of the projects to be paid for out of the new funds were scheduled for fiscal 1984 and 1985.

Annually, the GSA asks Congress for about $200 million for repair and alteration work on federal buildings, warehouses and support facilities, such as heating and cooling plants.

A House committee report on the legislation recommended making the cleanup of asbestos-laden federal buildings a priority, but the Senate took no such action. Both the House and Senate, however, specified that the bulk of the money be allocated to areas of high unemployment.

The GSA's preliminary plan, which Carmen must approve, sets aside $15.3 million for the District, where the unemployment rate is 10.3 percent. Among the states, New York, with an unemployment rate of 9.6 percent, would get the most money: $9.5 million. Indiana, with a 13.8 percent unemployment rate, would receive $9.2 million.

Preliminary estimates indicate that the Washington metropolitan area would get $19 million--the most of any area in the country.

Public Buildings Commissioner Richard O. Haase said the GSA could begin distributing the funds "within three days of the time President Reagan signs the measure into law. We expect to create a total of about 5,000 jobs, or about 40 jobs lasting 18 months for each $1 million."

The GSA has chosen "to expedite work that would be done in coming years," Carmen added. "There will be no make-work projects."

Dale Gottschalk, GSA's director of repair and alterations, said the "fast-track" projects locally will include:

* Repair of deteriorating rain leaders (internal downspouts) at the Agriculture Department's brick-faced headquarters at 14th Street and Independence Avenue. Estimated cost: $180,000.

* Repairing the roof of the Health and Human Services North Building: $445,000.

* Paving, painting and gutter repairs at the CIA headquarters in McLean: $100,000.

* Repair of a driveway at the U.S. Tax Court: $162,000.

* Sealing the exterior concrete at the J. Edgar Hoover FBI building against water intrusion: $275,000.

* Replacing a steam station conduit at the Interstate Commerce Commission: $100,000.

Nearly $3 million will be spent to repair facilities in Prince George's and Montgomery counties, including paving, sidewalk and curbs at the Suitland Federal Records Center and a new roof on one of the buildings at the complex. In Bethesda, the federal building's rest rooms will be refurbished for $40,000. The rest of Maryland would receive $2.2 million.

In Northern Virginia, where $1.1 million is allocated to repair projects, painting long delayed at the Pentagon will be accelerated and the roof of the heating plant near the Pentagon will be fixed for an estimated $150,000. For Virginia projects beyond Arlington, Alexandria and Fairfax, $2.1 million is allocated.

GSA officials have been unable to say how much of the $125 million will be used to abate asbestos problems. Asbestos, a carcinogenic substance, has been used for decades as an insulator in federal buildings.