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Water quality lab testing

Coliforms, reported as “Total Coliform,” are bacteria that are naturally present in the environment and are used as an indicator that other potentially harmful bacteria may be present. Standards for compliance vary depending on the size of the distribution system. In larger systems (including Evergreen, Edenvale, and Coyote Valley), 95 percent of all samples taken each month must be free of coliforms. In smaller systems (including North San José and Alviso), no more than one sample per month may test positive for the presence of coliforms.

Disinfection of surface water is necessary to destroy disease-causing organisms for the protection of public health. In Evergreen, North San José, and Alviso, water is disinfected using chloramine. Except for a slight chlorinous taste or odor, chloramine is not harmful to the general public. However, it must be removed for kidney dialysis machines and aquariums.  If you are receiving kidney dialysis treatment, please contact your doctor  or dialysis technician. For pet fish, contact your local fish store for more  information about special water treatment.

Fluoride is added to the treated water supplies in Evergreen, North San José, and Alviso to help prevent dental cavities in consumers.

The Evergreen community approved fluoridation with an advisory vote in the early 1960s. Muni Water does not fluoridate well water. As a result, some areas of Evergreen supplied with a blend of groundwater and treated water may receive fluoride levels slightly below the recommended range.

The SFPUC System-Wide Fluoridation Project (affecting North San José and Alviso) became operational in November 2005. The fluoride levels in the treated water are maintained within the range required by state regulations. In 2015, some areas of North San José/Alviso may receive a blend of non-fluoridated groundwater and SFPUC treated water. As a result, some customers may receive water with fluoride levels slightly below the recommended range.

At present, additional fluoride is not added in Edenvale or Coyote Valley service areas. Consult your doctor or dentist if you are considering additional fluoride supplements or treatments.

Hardness consists mainly of calcium and magnesium salts. Although it does not pose a health risk, it may be considered undesirable for other reasons. Some benefits to reducing hardness by using water softeners are reductions in soap usage, longer life for water heaters, and less incrustation of pipes. Some disadvantages are an increase in sodium intake (depending on type of softener used), proper maintenance/servicing requirements, and potential adverse affects on plants and landscaping.

Turbidity is a measure of the cloudiness of the water. It is monitored because it is a good indicator of the effectiveness of the water treatment process. The turbidity standard for unfiltered supplies (e.g., Hetch Hetchy) is 5 NTU. The turbidity for filtered water supplies (e.g., SCVWD treated water) must be less than 0.3 NTU 95 percent of the time, and at no time higher than 1 NTU.

Giardia Lamblia is a parasitic microbe found in most surface water. The SFPUC and SCVWD regularly test for this water-borne pathogen, and found it at very low levels in source water in 2015. However, current test methods approved by the USEPA do not distinguish between dead organisms and those capable of causing disease. Ingestion of Giardia Lamblia may produce symptoms of nausea, abdominal cramps, diarrhea, and associated headaches.

Lead, if present at elevated levels, can cause serious health problems, especially for pregnant women and young children. Lead in drinking water is primarily from materials and components associated with service lines and home plumbing. Muni Water is responsible for providing high quality drinking water, but cannot control the variety of materials used in plumbing components. When your water has been sitting for several hours, you can minimize the potential for lead exposure by flushing your tap for 30 seconds to two minutes before using water for drinking or cooking. If you are concerned about lead in your water, you may wish to have your water tested. Information on lead in drinking water, testing methods, and steps you can take to minimize exposure is available from the Safe Drinking Water Hotline at 800-426-4791 or at

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