DUBLIN (CBS SF) — Residents in a Dublin neighborhood are concerned about the safety of their drinking water after a sample test by officials last week revealed the presence of E.coli bacteria.

After hearing the news, local resident William Kuo told KPIX 5 he was happy that his family takes the extra step of using a reverse osmosis filtration system to further purify their drinking water.

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While worry and concern were sparked by the test results, Dublin San Ramon Services District spokeswoman Sue Stephenson said Kou and his neighbors have nothing to worry about.

“When we get a positive total coliform test, it’s saying you need to get more chlorine in the water,” Stephenson said.

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The water was treated and the delivery system in the Kuo family’s neighborhood and two others were flushed out several times.

In a second test — “Everything was clean, no problems,” Stephenson said.

She said California’s three years of drought was the likely culprit in the original test. Drought concerns — which were washed away by a wet winter — had limited her agency’s chances to flush out the system.

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“We had two years where nothing got flushed,” she said. “So we’re resuming flushing.”