EPHRATA — Crews removed the chlorine used to disinfect Ephrata’s water system Monday.

The cleaning of the system is tied to the city issuing an order Friday, asking residents to boil city tap water before using it. The cautionary step was taken after bacteria was found in several water samples last week.

The health advisory includes several precautionary steps people should take: Use boiled water or bottled water for drinking, brushing teeth, preparing food, dishwashing and making ice. Tap water should be boiled for one minute and allowed to cool before use.

Routine tests showed a single occurrence of Escherichia coli bacteria, commonly known as E. coli, on Wednesday afternoon. A second test of the same water came back negative on Friday morning, City Administrator Wes Crago said. After receiving the initial positive result, the city tested the water at two wells.

“The sample from one of the wells showed a preliminary indication of contamination,” he said in a previous interview. “The city and the Department of Health decided to act out of an abundance of caution and issue the health advisory.”

The contamination is non-acute coliform bacteria. The Department of Health Web site states the bacteria is not likely to cause illness.

Crews started disinfecting the system Friday morning, adding chlorine until the bacteria is removed from the system, Crago said.

The city sent 16 samples to the lab for testing. If all the samples test negative for bacteria, the water system can be recertified, according to the city.

Results may not be available for several days.

The city’s road and water project, which was blamed for a similar positive test for non-acute coliform bacteria last year, does not seem to be responsible for the bacteria, according to the city.

City well 6 is still being investigated as a possible source of contamination. Once the system is safe, the city plans to investigate what caused the problem and issue a report.