Water Quality

General Information

Water-Quality-TestingThe District is proud to declare that its water surpasses even the most stringent state and federal water quality regulations. Your drinking water has passed rigorous sampling and testing procedures before it reaches your tap. Most of the water you receive originates in the Colorado River and is treated extensively by Metropolitan Water District (MWD). In addition to MWD's testing, the District also conducts its own water sampling to ensure the quality of your water.

In fact, this year alone, the District had a certified lab run over 17,000 analyses in addition to the already thorough testing conducted by MWD before even a drop of water reaches your home or business.

Testing & Measuring Water Quality


Several steps are taken to ensure your water quality. Each week District staff collect water samples from special sampling locations that provide a representative analysis of water being supplied throughout the District. The water samples are collected in special sampling containers, refrigerated, and taken to a state-certified laboratory soon after the sample is collected. The laboratory uses state-of-the-art testing equipment and sophisticated measuring techniques to measure water quality down to the ppb (parts per billion) level. One part per billion is equivalent to the following:


  • One cent in 10 million dollars
  • One second in 32 years
  • One inch in 16,000 miles


271 S. Brea Canyon Road
Walnut, California 91789
(909) 595-1268    
(626) 964-6551
Monday-Thursday 7am-5pm
Friday 7am - 4pm