Until January, the Alexandria House condominium had sold only 30 of its more than 200 units in three years.

But since the Chase Manhattan Bank, the new owner-lenders who foreclosed on the building in November, restarted sales in mid-January, 130 more units have been sold.

Realtors familiar with Alexandria's condominium market said that sales also have picked up at several other condominium projects that previously had financial problems, partly because some have lowered prices and partly because few new buildings are being constructed while there still is an ample supply of empty units.

At least three condominiums that were foreclosed on by their construction lenders have slashed prices. Alexandria House, located near the city's Old Town district, cut prices by as much as $20,000 and lowered mortgage interest rates from 9 1/4 to 8 3/4 per cent, according to Jack Studnicky, anindependent consultant who is acting as Chase Manhattan's sales agent at the project. The units now cost between $40,000 and $90,000.

At the Hallmark, located at 200 N. Pickett St. in Alexandria's condominium-and-apartment-glutted Landmark section, prices have been reduced by as much as 25 per cent. Sales at Hallamrk were halted for a year after its developers were foreclosed on. Sales were started again March 6, according to John Wade, the president of the company selling the units. Still, Wade said 174 of Hallmark's 220 units are vacant.

At The Fountains, also located in the Landmark area at 301 N. Beauregard, between 30 to 40 units have been sold since February, according to sales agent Bert Spencer. The Fountains project was foreclosed on last fall. Prices for units there have been cut a minimum of 5 per cent, Spencer said. About half the building's 314 units now have been sold, she said.

Sales agents said that lenders are losing some money by cutting prices, but Spencer rated "Either you take a small loss or a much larger one by hanging on to the building" and not collecting any income from sales.

There is such an abundance of condominiums along Interstate Rte. 95 in Alexandria that it is known as "Condo canyon" because the buildings form a canyon-like corridor from the Capital Beltway north into Arlington County to the Rte. 7 interchange. Because of inflation and high construction loan interest rates, many of the units were overpriced, and because there were so many units available in one area, many went unsold.

John Wade, whose Condominium Realty Corp. sells condominiums, said he sold more than $1.7 million worth of condominium units in March in Alexandria. Sales have been steadily increasing over the past few months, he said.

Wade noted that such Alexandria condominiums as the Watergate, Templeton, Edsall Terrace, Edsall Bluffs, and Alexandria Knolls, among others, are either sold out, approaching 100 per cent occupancy, or have units that are now being resold by their individual owners. "There are many, many successful condominiums," Wade said.

James Dowden, executive vice president of a nonprofit national organization helps condominium owners, developers and lawyers, said that the Washington market never was depressed, compared to the situtaiton in places like Cleveland, Philadelphia, or Columbus, Ohio.

But Dowden conceded that the Washington area had "some disasters," in areas where there was overbuilding, units were overpriced, or owners tried to convert what were believed o be unprofitable rental buildings into condominiums.

Problems with overbuilding also occur with single-family home construction he noted.

Condominiums now are selling, Dowden said, because prices are lower and because there isn't enough other housing to meet the demand in the Washington area.

Condominium sales were also slow in Ocean City. Md., for much of 1975, but developers there also lowered prices, cut interest rates and accepted low down payments. As a result, sales improved markedly in 1976.

Condominium homeowners in Alexandria don't need to be told that their units are becoming more valuable.

Jerry Wilkerson, a public relations account executive, lives at the Place One condominium, which was foreclosed on by its lender. The property tax bill on his two-bedroom unit in Alexandria jumped 28 per cent this year, he said - even though he lives in a building that still is half empty.

"I got clobbered," said Wilkerson, who is appealing the assessment. "I'm not objecting to an increase, but comsidering the history of the building, I think 28 per cent is a little much."

Sales have gone so well at Alexandria House that Chase Manhattan's sales agent Studnicky said the condominium is having a "Thank You Alexandria Day" on April 23, with boat and bike races and an art festival, among other events.

"People who live in Old Town like Old Town and liked the building (Alexandria House), but wouldn't touch it with a 10-foot pole before because they knew it was in trouble," Studnicky said. "But they got interested again when the prices were reduced, and the place went like wild-fire."