The rules

Under the Safe Drinking Water Act, labs must be accredited and licensed to test drinking water.

In Ontario, the Ministry of the Environment, Conservation and Parks:

  • licenses laboratories
  • inspects laboratories
  • ensures that laboratories comply with laws and rules around drinking water testing

A drinking water testing licence authorizes a laboratory to carry out analysis for specific drinking water tests by approved analytical techniques.

If you are accredited to certain international standards, you can apply for a licence to test drinking water. The licence allows you to test drinking water for the parameters specified on your drinking water testing licence.

You will be granted a licence for at least one of the following parameter "classes":

  • microbiological
  • organic chemical
  • radioanalytical
  • physical/other
  • inorganic chemical

Prior to obtaining a drinking water testing licence, an inspector will conduct a pre-licence laboratory inspection.

Learn more about laboratory inspections.

The drinking water testing licence is valid for up to five years and an annual licensing fee applies. The drinking water testing licence indicates which parameters and methods a laboratory is licensed for under a specific class.

Laboratories must publicly display the drinking water testing wall certificate at the laboratory, so that clients know what classes a laboratory is licensed to perform. A copy of the laboratory's drinking water testing licence should also be available upon request.

Testing methods

Drinking water can only be tested using specific approved methods.

Before a laboratory can be licensed, an inspector will evaluate the methods your laboratory uses to test drinking water and verify that they meet requirements.

Learn more: approved drinking water testing methods

Sampling for chlorite and chlorate

Owners and operators of municipal residential drinking water systems must test for chlorite and chlorate when chlorine dioxide is used as a disinfectant and sampling is required by their Municipal Drinking Water Licence. Owners and operators of non-municipal residential drinking water systems that use chlorine dioxide may need to test for chlorite and chlorate.

Drinking water systems using chlorine dioxide treatment

To sample for chlorite and chlorate, contact your lab for detailed instructions. The following are general steps that are often followed when sampling for chlorite and chlorate:

  • Samples should be sparged (bubbled) at the time of collection with an inert gas (i.e., helium, argon, nitrogen) for approximately 5 to 10 minutes. Otherwise, residual chlorine dioxide will continue to form chlorite and elevate the results.
  • Add Ethylenediamine immediately after sparging. Ethylenediamine preservation for chlorite will also preserve the integrity of chlorate, which can increase in unpreserved samples as a result of chlorite degradation.
  • Place chlorite and chlorate samples in plastic or amber glass bottles and store in the dark at 5°C ± 3°C.
  • Submit the samples to the laboratory as soon as possible to meet laboratory holding-time requirements.

How to sparge (bubble) a water sample:

  • Collect the water sample in a wide-mouth container, making sure that the inside of the container does not come into contact with anything other than the water sample.
  • Connect a tube to the inert gas cylinder and insert a new glass pipette at the other end of the tube. Insert the other end of the pipette into the container so the open end is in the water but not touching the sides or bottom of the container.
  • Slowly open the inert gas and bubble the water sample gently and steadily for 5 to 10 minutes.
  • Remove the pipette and turn off the gas. Transfer the water sample to the pre-charged Ethylenediamine container.

Drinking water systems not using chlorine dioxide treatment

If samples are required or taken voluntarily by the owner, they must be preserved with Ethylenediamine at the time of sample collection, but sparging is not required. Submit the samples to the laboratory as soon as possible to ensure that laboratory holding time requirements are met.

Source law

You can find a complete set of provincial rules in:


Before you can apply for a licence, a laboratory must be accredited to perform specific tests under ISO//IEC 17025:2005. This is the international standard for technical competence and quality of laboratories.

The accreditation process includes:

  • assessing a laboratory
  • witnessing and reviewing test procedures
  • evaluating Quality Management System (QMS) and technical records
  • Proficiency Testing (PT)

There are two accreditation bodies recognized by the Ministry of the Environment, Conservation and Parks to accredit drinking water testing laboratories.

To get accredited, you can apply to either organization:

Standards Council of Canada
Phone: 613-238-3222

Canadian Association for Laboratory Accreditation
Phone: 613-233-5300

As part of the accreditation process, an audit is conducted to review and evaluate a laboratory’s testing methods.

The audit report will be provided to the Ministry of the Environment, Conservation and Parks as part of the licensing process — and must be shared with any person, if asked.

Applying for a drinking water testing licence

Once a laboratory has become accredited, an application for a drinking water testing licence is required to be completed and submitted to the Ministry of the Environment, Conservation and Parks. A drinking water testing licence will be issued to laboratories that are able to meet the regulatory requirements.

To apply:

Drinking water testing licence for laboratories located in Ontario:

Drinking water testing licence for laboratories located outside of Ontario:

Reporting to the ministry

Once a laboratory has become licensed to test drinking water, laboratories are required to upload test results to the ministry and must have a policy and procedure in place for this regulatory requirement. Additional information will be provided to you as part of the licensing and approvals process.

Laboratories with a drinking water testing licence

Download and complete the Drinking Water Laboratory Testing Licence form for the following circumstances:

  • Laboratory’s request for director’s direction - in the event of an emergency or other special circumstance, you can be exempted by a director’s direction to  conduct a test for a specific non-licensed parameter.
  • Application for a renewal licence to perform drinking water testing – a drinking water testing licence must be renewed every five years.
  • Application for a drinking water testing licence amendment/notification to ministry of laboratory changes – a laboratory may amend a licence to change or add new tests or testing parameters, remove a drinking water class or parameter, or update the laboratory name and/or contact information
  • Intent to voluntarily withdraw drinking water testing licence


  • Licence fee + 1 licensed class = $1000
  • Add additional test class = $250

Note: details of payment will be provided upon invoicing.

How to submit applications

Print, sign and submit the application form and any required attachments to:

Attention: Laboratory Licencing
Ministry of the Environment, Conservation and Parks
Compliance, Promotion and Support Branch
125 Resources Road
Toronto, ON M9P 3C6
Fax: 416 235 6519

For questions regarding the application and licensing process, please contact:

Ministry of the Environment, Conservation and Parks

Laboratory Licensing and Compliance Program