THE WATER WAS TURNED ON AGAIN the other day at the refurbished Temperance Fountain at Seventh and Indiana, Dr. Henry J. Cogswell's gift to the people of Washington to remind them of the evils of alcohol and to keep out of saloons. It was a grand occasion for members of the Cogswell Society, who had repaired to the fountain in "high spirits" from a local saloon.

Even though the restoration was done by the Pennsylvania Avenue Development Corporation, credit must also go to the Cogswell Society, which is one of the city's odder pressure groups. Its membership has been meeting in unsolemn secrecy since 1973 to imbibe liberally and keep alive the memory of the teetotaling founder of the fountain. You might say that the fountain and the society were made for each other.

Cogswell, who was born in Connecticut in 1819, made his fortune in the California gold rush in 1849 pulling teeth at $10 a tug. He went on to patent a number of inventions for false teeth, invest shrewdly in San Francisco real estate and devote much of the remainder of his life (which ended in 1900) to promoting his commitment to abstinence. His beneficences included the donation of 16 fountains of his own design to communities unwary enough to accept them.

Many of the fountains featured a statue of Cogswell in frock coat and full beard, but Washington's took the form of a small Greek temple with two dolphins intertwined within and a heron poised alertly on the roof. Around the fasciae is incised Cogswell's bold enlargement on St. Paul: "Faith, Hope, Charity, Temperance."

Washington's fountain is apparently the only one of Cogswell's watering places to survive unscathed. Indeed, it appears that only it and the fountain on the green in Rockville, Conn., have survived at all. Vandals tossed Rockville's bronze statue of Cogswell into nearby Lake Snipsic in 1885.

That's where the Cogswell Society comes in. Society spokesman Capt. Jay Coupe Jr., whose card identifies him simply as "Cavaliere della Republica Italiana" (pressed, he will acknowledge that he is also the press representative of the Joint Chiefs of Staff), swears that the society was formed after its creators noticed that a rusting coat hanger had dangled from the neglected heron's beak from 1960 to 1973. They also noted with relish how the Apex liquor store stood for years in the shadow of the monument to temperance.

The 12 founders thereupon called the society into being, took upon themselves the pledge to protect the fountain "against vandals both official and unofficial" and adopted a golden coat hanger as their symbol.

The Cogswell Society still limits itself to 12 members and meets monthly. But there have been some shifts in the membership since 1973. Dr. Michael Halberstam died in 1980, and TV host John McLaughlin and comic Mark Russell have transferred to associate status. The members pride themselves on never lunching at the same establishment twice. ("They wouldn't want us back anyway," says Coupe.)

It appears that the society's vigilance has paid off. The fountain gleams at its new location 50 feet or so north of where it once stood, and water runs from the dolphins' mouths for the first time in years -- though it's now shut off for the winter. But no longer is there thirst-quenching for passing man or beast. The horse trough is gone along with the horses and so is the cup on the chain that once served the human passers-by. The water is still nonalcoholic, but the idea has become distasteful.