The Tapps Island Association advised all of its water customers Friday to boil their drinking water after samples showed the presence of coliform bacteria.

Trace amounts of E.coli bacteria were detected in the water system on Tuesday, according to the association’s Web site. Retesting on Friday showed that coliform was present but did not disclose any trace of E.coli.

The association supplies treated well water to about 535 homes on the island and 10 homes off the island, said Don Lisko, interim general manager.

The association’s customers should use treated bottled water, or boil any water that might be consumed. That includes water for drinking, brushing teeth, dishwashing, preparing food, and making ice. Water should be brought to a rolling boil for one minute, and then be allowed to cool before use.

The Tapps Island Association is working closely with the Washington State Department of Health’s Office of Drinking Water to find the source of contamination and fix the problem, according to a Department of Health news release.

The water system at Lake Tapps is separate from but near the Bonney Lake water system.

Disinfecting the Tapps Island water system may be required. The boil-water advisory is in effect until further notice, the health department said Friday.

The association’s Web site warned the bacteria can make people sick and are a particular concern for those with weakened immune systems.

No illnesses related to the Tapps Island drinking water have been reported. The association is inspecting all of its water facilities to find the source of contamination.

Lisko said chlorine is being applied to the entire water system today and will be flushed out Sunday.

“Any time you have a situation like this you take it seriously,” Lisko said. “I’m hoping by Monday or Tuesday we’ll be back to normal.”

Notices of the boil-water advisory were hand-delivered to all of the system’s customers Friday night, Lisko said.

For more information, visit www.tapps-island.org or call Lisko at 253-266-2053.