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Recent Water Quality Testing Associated with Reports of Blue-tinted Water

Water testing was conducted last Saturday, February 9, 2019, by the City of Davis in response to a few customer calls from residents in South Davis related to blue tinted water. The analytical results indicate that the water the City delivers is colorless and that the constituents tested meet all State and Federal drinking water standards. No metals of concern were detected at concentrations that could cause health impacts in some areas of town have noticed a blue tint to the water in their home, specifically when filling a larger volume white basin or bathtub. The primary causes of water having a blue tint are the lighting in the area of the basin, or potential copper corrosion.

When light shines on water, some colors are absorbed and others are reflected. Typically, the deeper the water is, the more apparent the color. Light bulbs used in the interior of homes produce different types of light. Depending on the type of light used, it may change the color appearance of the water. The City does conduct annual color testing of the water supply, and those tests indicate the water is colorless.

Copper corrosion of interior plumbing can also create a blue-green color in water. This can be caused by a variety of factors, primarily low pH and stray electrical current from the homes electrical system. If the color of the water is due to copper corrosion, the resident may also notice some blue-green residue around faucets. Residential water heaters also have a corrosion protection device (called an anode). As the anode corrodes, it can leave some residue around faucets.

The City’s water supply, either from surface water or groundwater, is well under the regulatory requirements for copper. The typical pH of the City’s water supply is 7.5 to 8.0 units, well above the typical range that would potentially lead to pH corrosion of internal copper plumbing. In addition, the City adds an approved corrosion inhibiter to the water supply to assist in prevention of corrosion of water mains and copper plumbing in homes.

The City does not typically test water inside residential customer’s homes as the only control and regulatory requirement the City has on the water supply is up to the meter for each residence. Many factors are outside of the City’s control once water enters the property. Water softeners, home treatment systems (reverse osmosis), stray electrical current, and other factors may affect the quality of the water once it enters the home. In limited circumstances, such as recent events, the City will conduct some residential sampling to ensure that the water being delivered to the property meets all regulatory requirements. If you have concerns or questions regarding your water, the City does assist in troubleshooting common problems and provides a link to a State website of approved laboratories able conduct private water quality testing, at the homeowner’s expense.

For more information and for water quality test results of the water system and the results of the recent water testing please visit the city’s website at:
https://cityofdavis.org/city-hall/public-works/water/water-quality-information

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