The fail-safe systems designed to shut off the WSSC's main water treatment plant immmediately at the first sign of fire were being powered by a makeshift series of ordinary car batteries when fire severely damaged the plant last Wednesday.

The eight fail-safe systems all were powered by a single bank of high-voltage batteries at the time the fire broke out.

One source said yesterday that the "makeshift power bank either was too weak even with car batteries or that the fail-safe systems had been reconnected improperly after the makeshift rigging, leaving them without any power at all.

The systems failed to function when the fire broke out, an das a result fire swept virtually unimpeded through the plant, damaging it and triggering a continuing drinking water crists throughout Montgomery and Prince George' scounties.

WSSC officials refused comment yesterday, Spokesman Arthur P. Brigham said that the WSSC was awaiting completion of its own report - due Monday - on the causes of the fire and the reasons behind the failure of the fail-safe systems.

The causes of the fire are still undetermined, official said yesterday.

The fire broke out early Wednesday morning when a plant operator tried to turn on a water pump to insure that enough water was flowing through the system to meet morning demands throughout the two counties an portions of Howard Cunty.

The plant operator told officials that when the pump caught fire he pressed an emergency button to shut the pump off, but that it did not work. Had the station's circuit breaker fail-system been functioning properly, it would have shut down the plant at the first sign of electrical "fault" - in this case the fire. This would have prevented the fire from spreading so far so fast. WSSC officials have said.

The fire destroyed the plants' two main circuit breakers an two of four transformers used to send electrical power into the pumping station, crippling the plant's operation.

With only two transformers working, the plant could operate at only half its normal capacity last week and, as a result, residents in Montgomery and Prince George's were asked to restrict their use of water severely.

The WSSC is still asking residents to limit their water usage and to water their gardens only between the hours of 9 p.m. and midnight. The plant, when normally pumps about 170 million gallons of water into the bicounty water system daily, pumped only 30 million gallons into the system yesterday, according to Brigham.

The nakeshift car battery supplemental system was i nuse in the Potomac water treatment plant for about two weeks, one source estimated. The system was apparently never tested he said.

A spokesman for EII., the Baltimore firm that tests equipment for WSSC, said yesterday that the firm never checked the fail-state battery system during an extensive examination of the water treatment plant in June.

One engineer familiar with the fail-state power system requires batteries built especially for it. The use of any other batteries was "not proper," he said.

The fire also destroyed about one-third of the plant's main control panel, which left the plant without the use of five of its pumps.

The water crisis has been compounded by the low level of the Potomac River, which on Monday dipped lower than the level at which its waters can be efficiently pumped into the system. On Monday, the WSSC began installing a temporary underwater dam - called a weir - just downstream from the plant's intake pumps in an effort to raise the water level.

Brigham reported yesterday that the river, which registered 156.9 feet above sea level on Monday, had risen about a foot since the weir was installed. The water level must be at least 157 feet in order to be pumped efficiently. Brigham said.