Small Drinking Water Systems

Re-opening a SDWS after an extended closure due to the pandemic.

In accordance with O. Reg. 319/08, operators of Small Drinking Water Systems (SDWS) must notify the Health Unit of the proposed date to resume operation after being closed for more than 60 consecutive days and provide microbiological water test results. 

While operators of seasonal SDWS will be familiar with re-opening procedures, operators of SDWS that are normally open year-round may not be familiar with re-opening requirements. 

To comply, owners/operators must complete and submit the Small Drinking Water Systems Notice and Designation Form. Please note that in order to fully complete and submit this form, results from a recent water sample that has tested by an accredited laboratory must be attached.

If your business or premises makes or provides drinking water that’s available to the public and it’s not from a municipal drinking water system, you may be an owner or operator of a small drinking water system (SDWS) and be regulated under Ontario Regulation 319/08.

Public Health Inspectors will conduct an on-site risk assessment of the small drinking water system and determine what owners and operators must do in order to provide safe drinking water. The requirements will be issued through a directive for each system.

Ontario Regulation 319/08 (Small Drinking Water Systems) sets out specific requirements that owners and operators of SDWSs must comply with. They include:

Notice of Operation and Designating an Operator

Every owner and operator of a SDWS must provide specific information to the MOH in writing prior to re-opening after a 60-day closure, or after the construction, installation, alteration, or extension of the SDWS.

To comply with these requirements, owners/operators must complete and submit the Small Drinking Water Systems Notice and Designation Form.

Sampling and Testing:

Owners and operators of SDWSs are required to have water from their systems tested at a laboratory licensed by the Ministry of the Environment. Written notice identifying the laboratory must be submitted to the MOH by completing the Laboratory Services Notification (LSN) form. The minimum sampling requirement is for E.coli and total coliform bacteria. The directive issued by a Health Unit’s public health inspector may specify other tests that must be performed. These records must be kept for five years and must be made available, if requested by a member of the public, for a period of two years.


If a SDWS treats water, the owner and operator of the SDWS must ensure the water treatment equipment meets specific requirements that are detailed in Ontario Regulation 319/08. For systems that obtain water from a surface water source, the owner and operator must ensure appropriate treatment equipment is provided.

Reporting an Adverse Water Test Result 

As soon as you're aware of an adverse test result of your SDWS or if you see that the drinking water directed to users is not being properly disinfected, you must:

  • Make an immediate report to the MOH by speaking with someone in person or on the phone. If the Health Unit is closed, you can still report it to the on-call system at 519-739-4510.
  • You must also send a written notice to our Health Unit's MOH within 24 hours of when the initial verbal report is given. Fill out the Notice of Adverse Test Results and Issue Resolution form. Fax, email, or deliver the completed form to the Health Unit within 24 hours.
  • Contact the health unit if you require a sign for posting at the water source. For example, a “Do not drink”, “Public Notice”, or “Boil Your Water” sign.

Prepare a notice of issue resolution

When the issue is corrected you must deliver a follow-up written notice to our Health Unit’s MOH, summarizing the actions taken and the results achieved. Fill out the section "Summary of Actions Taken and Results Achieved" on the Notice of Adverse Test Results and Issue Resolution form. Fax, email, or deliver the completed form to our Health Unit within one week after you resolve the problem.

You can fax the completed form to 519-776-6102 (Attn: Environmental Health) or email it to us.

A SDWS Operator’s Guide is available from the health unit that has more detail on owning and operating a SDWS. For a copy of the guide, please contact the health unit at 519-258-2146 ext. 4475 or your request.

Blue-Green Algae Bloom

Blue-green algae are microscopic bacteria that occur naturally in fresh water lakes. In warm weather, with the right nutrients and low wind, they can form a large mass called a bloom. Residents and visitors are urged to take a cautious approach, monitor the situation, and protect themselves from potential health risks.