Water fountains were reduced to a dribble and toilets wouldn't flush properly on the top floors of the National Bureau of Standards 11-story headquarters in Gaitherburg yesterday morning. So employees took elevators down to lower floors where the water pressure still was strong.

By 2 p.m. however, as water pressure dropped like a thermometer and air-conditioners were turned down, the Bureau of Standard's 2600 employees were told to go home and its 24 buildings were put in a state of hot hibernation.

At the National Institutes of Health in Bethesda, suburban Maryland's largest single water user and where the facility's hospital's, laboratories office buildings and 12000 employees comsume more than 1.5 million gallons of water a day, employees were sent home at 4 p.m. an hour earlier than normal.

With NIH air-conditioners turned down or off temperatures inside scared above 90 degrees by 4 p.m. said AI Perkins, chief of the NIH design branch, quickly catching up to the 98-degree heat outside.

The federal health complex uses water-cooled air-conditioners that need an average of 250,000 gallons of water a day, an amount equal to the total water consumption of more than all but the top 10 suburban Maryland's water users.

The major consumers of water were among the first to be called yesterday after the area's main pumping station on the PotomacRiver was shut down by a fire. "Well, actually we on the radio," said NIH's Perkins, called them when we heard about it "to see how we could help."

Neighboring Howard County, which buys an average 1.3 million gallons of water a day from the Washington Suburban Sanitary Commission and is the agency's second largest customer was cut off late yesterday morning.

"But more than 80 per cent of our water comes from Baltimore so all we had to do was turn some valves to get water to residents near U.S. Rte. users who usually get WSSC water." said Howard County engineer James M. Irvin.

Howard County already is accustomed to water shortages, having lost WSSC water for several months following hurricane Eloise in 1975. Only last month a county-wide water shortage was declared requiring residents to water lawns and wash cars only on even-or odd-numbered days, depending on their house numbers.

Suburban Maryland's other major water users, such as the University of Maryland, which consumers over 1 million gallons a day at its College Park and other local campuses, also shut down early yesterday, with about 3,000 of its 5,000 employees told to go home at 2 p.m.

The campus has been between summer sessions and few classes were being held yesterday, "which helped 85 per cent," said Richard Horchler, a spokesman for the university. Last night's evening classes at University College, the adult night school, were cancelled.

While WSSC officials estimate the giant university uses about 1 million gallons of water a day. Charles Jantho, director of the physical plant, estimates 2-4 million gallons a day are used.

By closing most of the campus many cafeterias, dorm laundries and air-conditioners and by banning showers in the dorm, Jantho estimates that at least 1 million gallons a day can be served.

While major water users like the university federal complexes in Maryland, country clubs and shopping centers were "amazingly cooperative" in cutting back water consumption yesterday, thousands of small users declined to change their ways and were seen sprinkling lawns and washing cars.

At Maryland's off-campus fraternity houses students said they were taking their showers as usual. "I really don't think people on campus are too worried about it." said Gary Veisach of Sigma Alpha Mu. "There's still plenty of water."

There was much uncertainly yesterday about how long the water shortage would last and federal agencies dismissed employees early without any word about whether they were to return to work today. "Stay tuned to the radio," many NIH employees were told.

The list of major water users released by the WSSC yesterday revealed that one country club. Brooke Manor on Georgia Avenue in Rockville, uses an average of 331.000 gallons of water a day, six times more water than the next country club. Columbia in Chevy Chase. That figure places it among the top 10 water users in all of suburban Maryland. Burning Tree Consumes 57,000 gallons a day and Kenwood 54,000.

"I don't know why we use so much," said a club spokesman. "Probably most of it goes for the golf course and greens, refilling the pool and things like that." The club yesterday stopped watering the golf course and refilling the pool as soon as it was called by WSSC, the spokesman said.

Even agencies not using WSSC water, such as Andrews Air Force Base, yesterday voluntarily cut back on their water consumption. Andrews, which used to be a million-gallon-a-day customer of the WSSC, now gets all its water from the District of Columbia's Dalecarlia water plant, operated by the U.S. Army Corps of Engineers.

Andrews military police roamed the huge air base yesterday with loud speakers, in effect ordering those living on the base not to water lawns and wash cars until at least 8 a.m. today. Base civil engineer Col. Robert Reining Jr. said it should help free more D.C. water for transfer to the WSSC. Reining said the Air Force base reservoir began losing water this morning when the Army Corps of Engineers started transferring water to the WSSC.

Even relatively small water users such as soda bottling firms here, also voluntarily suspended operations yesterday to help save water. The Coca Cola bottling plant in Silver Spring which uses an average 142,00 gallons a day, producing about 25,000 cases of Coke, shut down at 11:30 a.m. A smaller Coca Cola plant in District Heights was not asked to suspend operations and did not.

The following are among the top water users, according to figures released yesterday by the WSSC. They figures, in gallons used per day, are not complete since many agencies and companies have several accounts with WSSC: