Division of Environmental and Community Health

Maine Center for Disease Control & Prevention

A Division of the Maine Department of Health and Human Services

DHHSMeCDCEnvironmental and Community HealthDrinking WaterPublic Water SystemsWater Sampling & Testing

Water Sampling and Testing


All public water systems are required to regularly sample and test their water to ensure that it meets federal and state drinking water standards, and is safe to drink. Without proper and timely sampling and testing, the quality of the water being served cannot be ensured.

Page Index

Testing Requirements

Accredited Laboratories

Sampling Guide

Sampling Instructions

Additional Resources


Drinking Water Testing Requirements

Each year in March, the Drinking Water Program provides a list of annual drinking water testing requirements, also known as Required Testing Sheets (RTS), to all public water systems. Required Testing Sheets detail the analytes (contaminants) that must be screened that year, the sampling frequency (i.e., monthly, quarterly, etc.) for each analyte, and the location in the system each sample should be taken. Systems that have not received a copy of their testing requirements can access that information online by clicking here. Questions and/or concerns regarding annual testing requirements should be addressed to your Public Water System Inspector.

Please be sure to follow these guidelines when taking compliance samples:

  • It is critical for systems to keep to the schedules outlined in their annual testing requirments, including taking samples during the scheduled sampling quarter.
    • 1st Quarter: January 1 - March 31
    • 2nd Quarter: April 1 - June 30
    • 3rd Quarter: July 1 - September 30
    • 4th Quarter: October 1 - December 31

    Remember: a Sampling Quarter is the same as a Calendar Quarter. Any samples that are required within a specific Quarter must be taken within the Calendar Quarter.

  • Carefully follow the directions for collecting the sample and completing the paperwork.
  • Make sure to always include your System name and PWSID# on all sample sheets/correspondence.
  • Bacteria samples must be taken within the distribution system at the pre-approved locations you submitted on your bacteria sample site plan. No compliance bacteria samples should be collected at the source unless it is the only public access to the water.
  • For small water systems that have no treatment, the entry point sample(s) can be taken from the first tap within the distribution system.
  • Be sure to contact your Public Water System Inspector before testing for Endothall or Diquat, to be sure that tests for those contaminants are required. Diquat, Asbestos, and MPA (Microscopic Particulate Analysis) are only analyzed in laboratories outside the state of Maine. Please contact the DWP if you are required to test for any of these contaminants.
  • Compliance sample results must be reported to the DWP.
    • When you take your sample to the accredited laboratory, make sure they know that it is for drinking water compliance and that the results must be sent to the DWP by the 10th day of the month following the sample collection period.
    • Follow-up with your lab to verify that your results were submitted to the DWP on time.
    • Remember: It is the Public Water System's responsibility to ensure water test results are reported following DWP guidelines.

To view an up-to-date report of compliance samples the Drinking Water Program has received and processed for your Public Water System, please click here.


Accredited Laboratories

The Laboratory you select must be certified in Maine to perform the tests you want to run on your water samples. Please visit the Laboratory Accreditation page of this website to obtain a list of all Maine certified commercial laboratories, or to ensure the lab you have chosen is certified to perform the tests you need to have run. You may confirm what tests are done by a laboratory or ask any other questions regarding laboratory quality by contacting Christine Blais, Laboratory Accreditation Officer: Email or phone (207) 287-3220.


Sampling Guide for Public Water Systems

This informational flyer (PDF) answers the questions,

  • Why is sampling important?
  • When do I need to sample?
  • What is a sampling quarter?
  • What happens if I miss a sample?
  • What are the sample collection locations and hold times by test?
  • How is a sample collected? What is a ground water rule source water tap?
  • Where can I find Monthly Operating Report (MOR) forms?

Water Sampling Instructions


Additional Resources

Updated 4/20/2023