Water Quality

MMWD takes many steps to ensure the water delivered to your tap is of high quality. These steps include responsibly managing our watershed lands and reservoirs, treating the water, operating and monitoring a complex distribution system, and maintaining and upgrading our facilities.

Annual Water Quality Report:  

Reporting Period of January - December 2018

We are proud to report that in 2018 as in prior years, your water continued to meet or
surpass all federal and state drinking water health standards. Our latest Annual Water Quality Report describes where your water comes from, what it contains, and how it compares to the state and federal drinking water standards. It also summarizes the results of the thousands of water quality analyses we conducted on your drinking water during 2018. Download the report in English or Spanish.


Every year, MMWD conducts more than 120,000 water quality and process control tests to ensure your water is safe to drink. MMWD looks for minerals, metals, salts and other similar chemicals. MMWD also tests for bacteria, herbicides, pesticides, endocrine disruptors, and industrial chemicals. In addition to the tests listed above, MMWD also tests your water to ensure the color and clarity are up to our high standards. 
Tests are conducted from the time the water is collected in our reservoirs on the watershed, to the time the water arrives at your faucet. This includes testing in the lakes, at the inlet and outlet of the treatment plants, at key locations in the distribution system, and some at customers' taps. If you have any questions about your water quality, please contact our Water Quality Laboratory at 415-945-1550 or through email.

Public Health Goals

As a California water supplier, MMWD must prepare a special Public Health Goals Report every three years with information about contaminants that exceeded Public Health Goals (PHGs) or the U. S. EPA’s Maximum Contaminant Level Goals (MCLGs). PHGs are non-enforceable goals established by the CalEPA’s Office of Environmental Health Hazard Assessment and are not required to be met by any public water system. The U. S. EPA establishes MCLGs which, like PHGs, are non-enforceable goals.  

MMWD’s PHG report, which summarizes water quality data for 2013, 2014 and 2015, was presented at a District Operations Committee meeting on July 15, 2016 and at a District Board meeting on August 16, 2016. If you have any questions regarding this report, please contact Chris Nanney, Water Quality Laboratory Manager, at (415) 945-1552.