Your Water Quality

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Seattle Public Utilities (our water provider) links:

NUD Water Quality additional info

Water Quality FAQs




Customers of Northshore Utility District enjoy water of very high quality.  Our water comes from the Tolt Reservoir, a protected watershed in the Cascade Mountains, and is delivered via the Tolt Pipeline.

How do we ensure your water is safe to drink?

Northshore Utility District purchases our water from Seattle Public Utilities (SPU).  SPU treats the water onsite for safety and quality at the Tolt Treatment Facility

After the water reaches our District, careful measures are taken to ensure it remains clean and pure. 

  • Remote monitoring systems on all reservoirs (water storage units) continuously track chlorine residuals, pH and temperature.  (Chlorine residuals protect drinking water from bacterial growth).

  • 90 water samples are drawn throughout the District each month.  Samples are tested for coliform bacteria and other regulated contaminants.  SPU tests for coliform bacteria approximately every three days.

  • Nearly 200 miles of water main are flushed each year to remove any sediment build-up.

  • All water mains are pressurized, disinfected, flushed and sampled before they are connected to the system and brought into service.        
  • All reservoirs are drained, cleaned and disinfected on a three-to-five year schedule.

  • All steel pipelines have been replaced with highly durable and resilient ductile iron pipe.

  • NUD's water quality officer oversees daily water quality programs, including an active Cross-Connection control program.

More info on additional water quality topics

If you have questions about water quality you may call or email our Water Quality Office at (425) 398-4419,

Click HERE to access your 2017 Drinking Water Quality Report