Providence Water, although a department of the City of Providence, is regulated by state and federal agencies in addition to city policies and procedures. The quality of our treated drinking water is regulated by the US Environmental Protection Agency and the Rhode Island Department of Health. Our revenue and rate structure is regulated by the Rhode Island Public Utilities Commission.

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Measurement Definitions

In order to understand what a chemical measurement means, one needs to have a basic understanding of the type of measuring units used, and what they mean. At Providence Water, the majority of our chemical determinations are measured using concentration units such as ppm and ppb, which stand for 'parts per million' and 'parts per billion', respectively.

But what is a ppm (or ppb) in plain English?

As an example, lets use the measured value of: Fluoride, 1.0 ppm. This value refers to one part of chemical (in this case fluoride) found in one million parts of our water. To realize how small a value this actually is, read the analogies listed below:

One part per million (ppm) equals:

  • 1 inch in 16 miles
  • 1 cent in $10,000
  • 1 minute in two (2) years
  • 1 postage stamp on the surface of a baseball diamond

One part per billion (ppb) equals:

  • 1 second in 32 years
  • The first 16 inches on a trip to the moon
  • Your first step in walking around the world 7½ times
  • 1 cent in $10,000,000
  • 1 inch in 16,000 miles

One part per trillion (ppt) equals:

  • 1 inch in 16 million miles (600+ times around the earth)
  • 1 cent in $10 billion
  • 1 second in 320 centuries