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Water Quality Notice

WATER QUALITY CHANGES February 1, 2021 and February 11, 2021
Water will continue to meet all regulatory standards

We are notifying you of expected changes in drinking water quality from the San Francisco Public Utilities Commission (SFPUC) on February 1, 2021 and February 11, 2021. The SFPUC is preparing for a Hetch Hetchy shutdown for approximately two weeks in February. Starting February 1st, SFPUC will be reducing the Hetch Hetchy flow and supplementing with water from local sources through the Sunol Valley Water Treatment Plant (SVWTP). On February 11th, the Hetch Hetchy flow will be shut down until approximately February 24th.

The changes below will likely affect Stanford approximately 24 hours after the date noted below (average travel time from East Bay facilities to Stanford).

Expected Water Quality



SFPUC as of 1/28/21:
Blend (Hetch Hetchy)

SFPUC as of 2/1/21:
Blend (SVWTP & Hetch Hetchy)

SFPUC as of 2/11/21:
Blend (SVWTP)

Chlorine residual (total) mg/L 3.0 3.0 3.0
Free Ammonia-N mg/L 0.07 0.04 0.04
pH pH 9.5 9.6 9.2
Turbidity NTU 0.3 0.2 0.1
Conductivity µS/cm 50 60 239
Hardness mg/L 9 16 73
Alkalinity mg/L 13 16 68
TOC mg/L 1.1 1.2 2.1

What does the water quality change mean for equipment and processes in laboratories?

Equipment and processes in labs or academic buildings may be affected by fluctuations in hardness, alkalinity, and conductivity over the transition. 

To be notified of domestic water quality blend changes in the future, sign up to receive automated emails from our drinking water quality list serve

Water Quality Background Information

During normal operations, 100% of the domestic water delivered to the Stanford campus comes from the San Francisco Public Utilities Commission (SFPUC). The water is delivered to Stanford University and has already been treated and disinfected with chloramine (the water is also fluoridated and the pH is adjusted for corrosion control). Stanford does not apply additional treatment to the water received from SFPUC.

Portable chlorine residual testing device
Chlorine residual testing

The source water from SFPUC is typically from the Hetch Hetchy reservoir located in the Sierra Nevada Mountains. Occasionally the source water will shift to local reservoirs during routine maintenance to the conveyance system. During most years, there will be a 30-day shut down of the Hetch Hetchy source in the winter months. More information about this and any other anticipated water quality will be provided through this website and our water quality list serve ahead of planned operational changes.

In addition, sensitive water users on campus should be aware that in the event of an emergency or other operational need, on-campus groundwater wells would be used to supplement or replace the domestic water supply that typically comes from SFPUC. The groundwater from on campus groundwater wells will have significantly different water quality than what is typically received from SFPUC. If you have operations that are sensitive to changes in hardness, dissolved solids, and pH, you should plan for alternative operations during such a change to protect processes, equipment, and/or research. We will send notices through the water quality list serve if groundwater will be introduced into our drinking water distribution system.

Average Water Quality

Below is a summary of average water quality in various treated source waters. The reliability, safety, and high quality of drinking water is important to us. If you have any questions, or would like to discuss further, please feel free to contact us



SFPUC Treated Surface Water
(Source: Hetch Hetchy)

SFPUC Treated Surface Water
(Source: Sunol Valley Water Treatment Plant)

Stanford Groundwater Wells
(Source: On-Campus Groundwater)

Chlorine residual (total) mg/L 2.8
(could be blended with SFPUC [chloramine] or treated on campus [free chlorine])
Free Ammonia-N mg/L 0.05 0.05 0
pH pH 9.6 9.0 7.0 - 7.8
Turbidity NTU 0.3 0.1 0.8
Conductivity µS/cm 47 234 990
Hardness mg/L 8 66 400
Total Dissolved Solids mg/L 25 195 600
Alkalinity mg/L 16 65 300
Silica mg/L 3 - 5 3 - 5 25