Surface Water
Treatment Rule

If a public water system uses a lake, river, stream or pond as it's water source, then it is regulated by the Surface Water Treatment Rule.  This rule seeks to prevent waterborne diseases caused by viruses, Legionella, and Giardia lamblia. These disease-causing microbes are present at varying concentrations in most surface waters. The rule requires that water systems filter and disinfect water from surface water sources to reduce the occurrence of unsafe levels of these microbes.


Does the Surface Water Treatment Rule apply to my water system?

This rule applies to all Public Water Supply Systems (community and non-community) using a surface water source (i.e. water open to the atmosphere and subject to surface runoff) or groundwater source under the direct influence of surface water.

Surface Water Treatment

  • As of December 17, 2001, the turbidity standard has been reduced to 0.3 turbidity units (NTU).
  • New filtration criteria, disinfection criteria and monitoring requirements are effective as of December 17, 2001.

For surface water systems, chlorine is monitored at the entry point and throughout the distribution system.

Actions your water system should be taking

  • Public water systems must be operated by personnel that meet qualifications specified by the State or EPA.  The water purveyor is required to monitor the water system, by sampling and testing the water, for compliance to the Maximum Contaminant Levels listed for the public water system category (community, non-community, etc.).
  • Treatment must remove or inactivate at least 99% of Cryptosporidium, 99.9% of Giardia Lamblia cysts, and 99.99% of viruses; all systems must disinfect, and filter.  Criteria must be met for determining if treatment (turbidity removal, disinfection) is adequate for filtered systems.
  • System using surface water must send in monthly reports to the State documenting compliance with treatment and monitoring requirements.

Water users must be informed through public notification, of any violation.