The kaleidoscope of Washington-area thrift institutions is shifting as the result of mergers. Three have been approved recently and one already has taken place. Two more mergers await regulatory action.

By early next year, the number of federal savings and loans associations in the District is expected to decrease from 16 to 11. Their current ranking by asset size also will be affected.

Perpetual, whose union with American was approved Oct. 30 by the Federal Home Loan Bank Board, will remain the leader with $1.5 billion in combined assets. Second in asset size to Perpetual American, as the institution is now known, will be an association formed of Columbia and First Federal. These two S&Ls now rank third and sixth.

Together, as Columbia First, they will have $940 million in assets and edge out the current second runner, National Permanent. T. William Blumenauer, Columbia's president, said Bank Board approval is expected next month or in early January. The actual merger will take place 45 to 60 days after that.

National Permanent plans to acquire Eastern Liberty. Its name will remain the same, but National Permanent will slip to third place with $930 million, based on current asset size. Application for merger was made within the past month, so no action is contemplated until sometime next year.

The fourth spot will belong to Interstate which will take over Metropolis Jan. 1 following approval Oct. 30. The augmented Interstate will have $518 million in assets. The next largest is Washington Federal with assets of $367 million.

The fifth District merger involves Capital City and Northwestern, 10th and 12th largest respectively. Capital City, the survivor, with $304 million in assets, will jump to sixth place. Seventh largest of the 11 surviving District S&Ls will be Home, with assets of $227 million, followed by Jefferson with $154 million, Independence with $56 million, OBA with $24 million and Community with $23.6 million.

None of these has any plans to merge at the moment. However, Community President Orlando W. Darden said his association is currently reviewing all options including merger and conversion to a stock association.

Across the Potomac, First American Savings and Loan of Woodbridge plans to merge with Newgate Savings and Loan of Burke Dec. 1 if their stockholders approve. The survivor will be First American, with $130 million in total assets. Another merger involves United Savings and Loan of Vienna, assets $63 million, with Virginia First Savings and Loan of Petersburg, assets $211 million.

No mergers of thrifts in nearby Maryland have been announced. However, both suburban thrifts and their larger neighbors in the District will find increased competition from Baltimore associations moving into the area. Loyola, Federal Savings and Loan, which has $1.2 billion in assets, plans to open a new Bethesda branch next month. It already has offices in Silver Spring, Largo, Bowie, Laurel and Greenbelt.