Excessive levels of lead and copper, about 100 times the federal standard, have been found in the drinking water at the Madison Building of the Library of Congress, a spokesman there said yesterday.

Thirty-one employes have reported stomach cramps, nausea or diarrhea after drinking water from the fountains in the building, but there have been no serious illnesses, said Nancy Bush, public information officer for the Library of Congress. Employes who believe they have become ill because of the water are being offered free health tests, Bush said.

She said recent tests show the water is clean, but the library is awaiting written confirmation from the Army Corps of Engineers before turning on the drinking fountains, which have been shut off more than two weeks.

Officials from the Library of Congress and the employes unions met with representatives of the Corps of Engineers yesterday to hear a report on all the tests done on the water.

An April 9 test showed 3.6 parts of lead per million; the federal standard is .05 parts per million. The tests also revealed 112 parts per million copper; the proposed federal standard is 1.3 parts per million, said Arnold Kuzmack of the Office of Drinking Water at the U.S. Environmental Protection Agency.

"That's 100 times the standard, and they would be advised to get it cleared up quickly," Kuzmack said. "If you were dying of thirst in the desert, you would be advised to drink that water, but in a regular situation you would be advised to avoid it."

Excessive levels of lead have been determined to cause neurological problems in small children, Kuzmack said. "For adults, even in low levels there's some proof it causes high blood pressure," he said, noting that that is one reason the EPA recently recommended reducing the level of lead allowed in drinking water from .05 parts per million to .02.

The copper is probably of less concern, he said.

The problems began March 12, when someone put the wrong filter in the drinking water system, said Elliott Carroll, executive assistant to the Architect of the Capitol, the office responsible for maintenance of the Library of Congress.

"The filter was safe, but it was a filter used for kitchens in cafeterias and it gave the water a bad taste," Carroll said. On March 24, to correct the problem, pressurized water was used to flush out the water system.

The flushing stirred sediment and apparently was responsible for the copper and lead, Carroll said. When employes complained of the taste and discoloration, signs were posted that said, "Do Not Drink The Water." On March 25, water samples were sent to Corps of Engineers for testing, Bush said.

The library sent a notice yesterday offering free testing to any workers who had suffered nausea, diarrhea or stomach cramps, or who drank the water while pregnant. But some employes are concerned that the contamination might have preceded the March 24 flushing.

"They don't really know the cause, so how do they know how long the toxic substance was present?" asked one employe who recently had a child. "The baby seems fine. My concern now is that I still have lead in my system now and I'm nursing the baby."