A routine monthly sample of the Rhodena Beach Water District’s water supply turned up stomach-turning results — E. Coli bacteria.

Crews learned Thursday that the bacteria, which can cause nausea, diarrhea and headaches, was present in the system. It is unknown how much of the bacteria is present, said King Water owner Clive Defty. King Water operates the reservoir and water system for the area, which is south of Coupeville on Snakelum Point.

The test results prompted King Water to advise the approximately 60 households that it serves to boil their water before any use. According to a notice delivered to its customers, boiled or bottled water should be used until further notice.

“We’ve taken six additional samples from each area to determine if it was a positive, or a false alarm,” Defty said. “There is always a margin of error … which is why we do repeat tests.”

The results of the follow-up tests will not be known until today. If the tests come back clean, Defty said the boil order will be lifted.

“If, indeed, the tests show the water is contaminated, the question is ‘How on earth did it get contaminated?’” Defty said.

Immediately following the sampling for the secondary tests, crews treated the entire system with chlorine to kill the bacteria. If the follow-up tests confirm the contamination, chlorination will continue through the weekend, Defty said.

The notice advised people with weak immune systems to be especially diligent with their water supply.