Public Water Systems

  1. Water Consumption
  2. Water Leakage

Data Table


A Public Water System is an entity that provides water for human consumption through pipes and other constructed conveyances. Roughly 75% of Thurston County residents get their water from a public water system. Public water systems are regulated by the state Department of Health to ensure the water produced is safe to drink. Systems fall into two categories:

  • Group A Systems provide water to at least 15 service connections or serve at least 25 people for at least 60 days a year.  Group A systems are subject to federal standards found in the Safe Drinking Water Act and state standards found in Chapter 246-290 WAC.
  • Group B Systems have 3 to 14 service connections and either serve less than 25 people per day or 25 or more people per day during a period less than 60 days per year.  Group B systems are subject to state standards found in Chapter 246-291 WAC

Public water systems serve the public but may be publicly, privately, or cooperatively owned. The state Department of Health identifies seven public water system ownership types:

  • City/town
  • County
  • State
  • Special district, such as Thurston PUD
  • Association, such as a home owners association
  • Investor
  • Privately

City/town-owned systems produce about 80% of total water produced.

Around 98% of the water produced by public water systems is fully metered (meaning all customers have a water meter). Meters help system managers track the effectiveness of efficiency programs and monitor water loss through leaks. Larger water systems generally have lower and more stable distribution system leakage rates. Between 2010 and 2022, city- or town-owned water systems maintained a leakage rate of less than 10%. Leakage rates can only be calculated for systems that are fully metered.

Total Water Produced, Authorized Consumption, and Distribution System Leakage

Total Water Produced − Authorized Consumption = Distribution System Leakage

Total Water Produced is the amount of water pumped and dispersed from each water system’s source.

Authorized Consumption, is the total amount of water used by customers, based on data from customers' water meters.

Distribution System Leakage is the difference between Authorized Consumption and Total Water Produced. Leakage may result from several causes including leaky pipes and valves, storage overflow, and unauthorized or unmetered consumption.


  • Washington State Department of Health