Savers withdrew significantly more money from their thrift accounts last month than they put in, according to preliminary industry reports. This is the first time since the recession year of 1974 that savings and loan associations have recorded more withdrawals than deposits.

While the Federal Home Loan Bank Board has no figures yet, Michael Sumichrast, chief economist for the National Association of Home Builders, this week estimated that April losses nationwide could go as high as $400 million. Kenneth Thygerson, chief economist for the U.S. League of Savings Associations, said in an interview he believes that 20 to 30 percent of S&Ls were running in the red last month.

Saul Klaman, president of the National Association of Mutual Savings Banks, said member banks have been "absolutely clobbered in April" and added the outflow of funds had been particularly acute in New York City.

Locally, the Metropolitan Washington Savings and Loan League calculated that 16 District thrifts had a collective net outflow of $45 million in April. According to Ralph Childs, its president, every S&L in the city lost deposits. Some of the losses were "astronomical," he said. In April alone, Home Federal Savings and Loan, which he heads, lost all the gains it had made in the first quarter.

The loss for 46 area S&Ls amounted to $48 million. Industry sources offered several reasons why District thrifts were harder hit, including more corporate customers, more sensitivity to interest rates and more need for cash.

Charles Kresslein of the Maryland league estimated half of its members experienced negative outflows last month. He put the losses suffered by 25 S&Ls throughout the state at $4 million.

April withdrawals from savings accounts are customarily high due to income tax needs. For example net deposits dropped from $2.6 billion in March 1978 to $400 million in April 1978. This year they fell much more sharply, from $3.1 billion to minus $400 million, if Sumichrast's estimate proves correct.

The losses come on the heels of one of the best months experienced by S&Ls. After credit for payment of interest, March's net savings gain was $8.2 billion, a record.

This month's decline can be directly attributed to decreased sales of money market certificates by S&Ls. Last March 15 federal regulators eliminated the interest compounding and differential that had made thrift certificates more attractive than Treasury bills or those sold by banks. The move was calculated to help cool the economy.

The result has been a large shift in funds away from thrifts and into other investments. The American Bankers Association reports "some growth" in money market certificates. Money market mutual funds experienced a 12 percent gain in April. Their assets, which the Investment Company Institute says are increasing at an accelerated pace, totaled $19.7 billion in April, up from $6 billion a year earlier.

The average weekly volume of noncompetitive Treasury bills increased substantially between March and April, compared with sales a year earlier. Sales of 13-week bills averaged $504 million a week in April, up 30 percent over the previous month. In 1978 the comparable increase was 9.5 percent. For 26-week bills there was a monthly increase of 16 percent, compared with a decrease of 13 percent last year. Virtually all individual investors make non-competitive bids, although some institutions do too.

The last time disintermediation occurred was in 1974. Negative outflows were recorded for four months between April and September, when losses reached a record $1,068 billion. As a result housing starts plummeted. The country slipped into a recession.

Last spring when a similar situation threatened, Federal Home Loan Bank Board chairman Robert McKinney authorized S&Ls to offer the $10,000, six month money market certificate, whose interest rate was tied to the six-month Treasury bill rate. Sales volume was high but so were the costs of paying interest, sometimes in excess of 10 percent.

In an interview yesterday the Metropolitan League's Childs called the money market certificate a "Band-Aid approach." He charged it just postponed an inevitability and "perhaps exacerbated the situation by giving a false sense of security to the economy and financial institutions."

Childs said that if the trend continues into May, a mortgage crunch can be expected by the third quarter of this year. However, he added he did not think it would be as serious as in 1974 because the economy is in better shape. Thygerson of the U.S. League concurred, noting that liquidity stock-piled in the first quarter should keep mortgage funds available until fall.