State and local governments have done an inadequate job of enforcing the 1974 law designed to ensure that the nation's drinking water is safe, the General Accounting Office has concluded.

The GAO study found that compliance with the regulations of the Safe Drinking Water Act of 1974 "in literally thousands of cases appears to be the exception rather than the norm."

President Reagan's federalism program envisions turning many enforcement and aid programs over to the states. But some critics, including many state officials, contend that the states will be ill-equipped to carry them out.

In fiscal 1980 the Environmental Protection Agency found more than 146,000 violations by 28,000 of the nation's 65,000 community water systems, according to the study. The GAO's investigation of 140 community water systems identified 701 violations by 93 of the systems.

The EPA held hearings on the safe drinking water program last month, and the staff is analyzing the comments received. The staff plans to present its analysis at the end of the month to the National Drinking Water Advisory Council, which is to forward its recommendation to EPA Administrator Anne M. Gorsuch.

The Safe Drinking Water Act gave the EPA the authority to establish national health standards for drinking water and to delegate primary enforcement responsibility to the states.

It has given that responsibility to all states except Indiana, Iowa, Oregon, Pennsylvania, South Dakota and Wyoming and the District of Columbia.

States are expected to ensure that water system operators periodically test their supplies and notify their customers whenever the system fails to meet one of the standards or when a required test is missed. The GAO said that, of the 146,000 known violations in 1980, the public was notified in 16,000 cases.

The GAO cited the lack of state and local resources, both financial and in terms of personnel, and apathy on the part of system operators as major problems.

It cited, for instance, the Fredericksburg Water Association, a small system in Martinsburg, Pa., that serves about 200 customers. In 1980 the system failed to test the water for coliform bacteria, which indicates fecal material, in 10 of the 12 months such tests were required. The reason: the water system operator worked full time as a truck driver and could do the tests only in his spare time.

Similarly, in Bradley, Okla., the water system operator manages a service station and does the testing when he can get around to it, the GAO said.

State enforcement procedures also were found to be deficient. For example, West Virginia had tested only 83 of its 504 water systems properly for various types of contaminants. West Virginia officials attributed the problem to reduced state funding, inflation and not enough federal funds.

The GAO said that the continued use of thousands of toxic chemicals underlines the need for careful testing of water supplies. The latest statistics available indicate that, from 1961 through 1978, contaminated drinking water caused 101,243 recorded illnesses and at least 22 deaths. The GAO said water experts estimated that the figures could be 10 times higher.

But the GAO said it could point to no instances of deaths or serious illness resulting from the problems it identified.