Office of Drinking Water Quality

MONITORING Public Water Supplies

All water supplies are monitored for potential contaminants. What we test for, and how often, depend on the type of system and how many people drink the water. Click on the system type to find the initial monitoring requirements.

• Transient water supplies are tested for nitrates and bacteria only. These can have immediate health effects.
• Non-transient and Community water supplies are tested for nitrates and bacteria, along with about 70 other potential contaminants that can have long-term health effects if consumed daily over many years.
• The number of samples that each system must take per week depends on the number of people they serve.

The US EPA "Safewater" web site has more on monitoring of public water.

Rhode Island's monitoring requirements are contained in the Regulations

If contaminants are detected in amounts above certain limits, the supplier is required to take action. The action may be:

• A change in treatment to reduce the amount of the contaminant detected, or
• Public notice, if there is any danger to consumers in the short term, or
• If the contamination is severe, the water supplier may be required to provide bottled water to consumers until the problem is resolved.

For a complete list of potential contaminants, go to the US EPA's web site at http://www.epa.gov/safewater/mcl.html. There you will learn the maximum levels allowed, and how these levels are set.