The discolored water than some Montgomery County residents discovered when they turned on their faucets yesterday and the day before resulted from an accident at the Potomac River water filtration plant, according to a Washington Suburban Sanitary Commission spokesman.

WSSC spokesman Arthur Brigham explained yesterday that "harmless" particles, which some Bethesda residents dicovered in their water, actually were iron deposits at the bottom of their water pipes that had become disturbed after a valve inadvertently was thrown at the water plant.

"Its been very bad for two days. The water is brown, polluted and dirty," said Meryl Steigman, a Bethesda housewife who complained yesterday to WSSC.

The water became muddy Monday, according to WSSC spokesman Brigham, after a contractor - working on damaged electrical gear at the Potomac water olant - accidentally triggered a valve causing the flow of water to reverse momentarily in Bethesda area water pipes.

Brigham said yesterday that the number of complaints had subsided and there were only three "reported" cases on which WSSC was working.

"The discolored water should have settled by now in most cases," said Brigham, who added that WSSC maintenance men were flushing out lines where iron water pipe filings out lines where iron water pipe filings continued to be a problem.

Brigham said the dicoloration of water lasted longer in areas such as dead end streets where the water pipes did not immediately connect to the main water system.

The WSSC spokesman advised water users to fill up containers with water and let the pipe filings settle before drinking the water.