Ultraviolet disinfection

Ultraviolet (UV) disinfection is a well-established method for disinfecting drinking water.

As water passes through a UV unit, an ultraviolet range of light inactivates pathogens that may be present in the raw water, including:

  • viruses
  • bacteria
  • protozoa

Maintaining your ultraviolet system

Maintenance for your UV equipment is not only important to treat your drinking water – it is the law! Maintenance requirements for water treatment equipment are outlined in Schedules 8 and 9 of the Drinking Water Systems Regulation (Ontario Regulation 170/03) under the Safe Drinking Water Act, 2002.

By properly maintaining your UV unit you can:

  • better protect the people who receive drinking water from your system
  • reduce your risk of getting adverse test results, which will cost you time and money to correct
  • help you to stay compliant with your legal requirements and avoid potential enforcement action and costly penalties

Maintenance requirements

You are required to maintain your UV unit in accordance with the requirements listed in:

  • your Engineering Evaluation Report (EER)
  • the manufacturer’s manual if there are no maintenance requirements in the EER
  • Schedules 8 or 9, as applicable, of Ontario Regulation 170/03, if there is no EER or manufacturer’s manual available
  • a ministry approval, where applicable

Typical maintenance activities

You are required to maintain your treatment equipment and record maintenance activities.

Where the EER or manufacturer’s instructions do not require maintenance activities, we recommend you undertake all of the following typical maintenance activities to help ensure the safety of your drinking water.

Changing your UV bulb

UV bulbs should be replaced on a set cycle or based on lamp life (for example, number of hours of use). The lamp life is dependent on the quality of the raw water.

Most UV units feature an audible or visual alarm to warn users that the bulb needs replacement.

Cleaning your quartz sleeve

The quartz sleeve is a protective cover for the UV bulb to keep it dry.

A cloudy quartz sleeve lowers the UV unit’s effectiveness. The quartz sleeve should be inspected and cleaned.

Cleaning frequency may depend on the characteristics of the raw water. If there are no EER/manufacturer’s instructions, the sleeve should be checked every 3 months and cleaned when necessary.

Some UV units include an automatic sleeve cleaning feature. Check your manufacturer’s instructions to confirm if your unit has this feature.

Confirming your UV automatic shut-off is working

The automatic shut-off functionality should be checked and tested every 3 months.

A functional automatic shut-off valve stops the flow of water in the event of an equipment malfunction, loss of power or improper disinfection.

Not all UV units include automatic shut-off as a standard feature. On many models, an automatic shut-off valve is an optional add-on. Check with the manufacturer to find out if your unit has an automatic shut off valve. If it does not, ask if the unit can be upgraded to add this important safety feature.

Your manufacturer’s instructions should include how to test your UV unit. A common way to test the valve functionality is to unplug the unit to verify that it shuts down. This is important to ensure no improperly disinfected water is directed to your consumers.

Confirming your UV alarm is working

The alarm should be tested every 3 months.

If your UV unit does not have an automatic shut-off valve and an alarm signal, the certified operator/trained person must immediately respond and take action.

If your UV unit has an automatic shut-off valve, there is no requirement to respond immediately since the flow of water should be stopped.

Cleaning your sensor

The UV sensor should be cleaned and inspected every 2 months and calibrated annually.

If cleaning is not done regularly, the sensor will inaccurately read incoming UV light and may jeopardize the safety of your water.

Who can maintain your ultraviolet equipment

Maintenance of your drinking water system treatment equipment is the responsibility of your certified operator or trained person.

For more information on operator certification:

Documenting your maintenance

The certified operator/trained person must record any UV equipment maintenance, checks and adjustments.

All records of maintenance activities must include the:

  • date
  • time
  • name of the individual making the record

We will ask to see this documentation during an inspection.

For more information on how to prepare for an inspection, visit what to expect when an environmental or water compliance officer inspects your facility.

Replacing and upgrading ultraviolet units

National Sanitation Foundation 55 Class A (NSF 55 A) certified units

We strongly recommend you use a UV unit that is NSF 55 A certified.

Certified units are equipped with automatic shut-off valves, sensors, flow restrictors, and alarms. They are designed to provide adequate disinfection of drinking water for your users.

The owner’s manual or your EER should tell you if your UV unit is NSF certified. We may consider other UV units as equivalent to NSF 55 A if they provide:

  • a minimum of 40 mJ/cm2 at maximum flow
  • a minimum of 75% UV transmittivity (the ability of UV light to go through water)

Your latest EER will include specific details about the UV units installed at your system, including the UV dose delivered and the maximum flow capacity. If your current unit is not NSF certified and does not appear to be equivalent, we recommend you replace your unit.

Replacing your UV unit with a similar unit

You are allowed to replace UV units with a different make or model without updating the system’s EER if the new unit:

  • delivers the same UV dose as the original unit
  • has the same maximum flow capacity as the original unit

Your supplier, or a licensed engineering practitioner who has experience in sanitary engineering related to drinking water systems, should be able to review your EER and verify that the proposed unit matches your existing unit.

We strongly recommend you install an NSF 55 A UV unit when replacing your unit.

New UV units must be equipped with a sensor and an automatic shut-off or alarm functions to meet regulatory requirements.

Upgrading your UV unit

Replacing UV units with makes or models that deliver a different UV dose or have a different maximum flow capacity must be done in consultation with a licensed engineering practitioner who has experience in sanitary engineering. 

The practitioner must also prepare an updated EER no later than 30 days after the new UV unit is in service.

You must submit a Declaration of Licensed Engineering Practitioner and Notice of Completion form to the ministry if you are upgrading your UV unit.

If you have any questions about registration, call the Registration Help Desk at Toll-free: 1-866-793-2588.

Tips for automatic shut-off functions

An automatic shut-off valve is a device which is used to automatically stop water flowing through the UV unit when the sensor has determined an inadequate level of treatment is being provided. This may occur a during a power outage or if the UV bulb is not  supplying enough light intensity for disinfection.

We recommend that you install an alarm to notify the certified operator/trained person when an automatic shut-off has occurred.  This allows the certified operator/trained person to address the problem promptly and take action to restore disinfection.

Report a problem

If your UV disinfection unit, automatic shut-off or alarm feature fails and improperly disinfected water may have been directed to users of the system, an adverse water quality incident must be reported.

You must make an immediate verbal report (by telephone or in person) to:

  • your local medical officer of health at the local public health unit
  • the ministry’s Spills Action Centre Toll-free: 1-800-268-6060, open 24 hours a day and 365 days a year
  • the operator of each designated facility (for example, long-term care facility, child care centre) served by your system if that operator is someone other than yourself

You must speak to someone in person or on the phone. Leaving a voicemail does not fulfill your requirement to make an immediate report.

You must also take corrective action and make written reports. 

For full information on the steps you must take to report and respond to an adverse water quality incident, read the following sections related to adverse test results and other problems in the applicable guide:

Changes to your drinking water system information

For any changes to your drinking water system (for example, contact information or upgrading your UV unit), complete a Drinking Water System Profile Information form.

Select the “Update Existing Registration” option and only fill out the information that has changed.

You must email the form to waterforms@ontario.ca within 10 days of the change.

If you have any questions about your system’s registration, call the Registration Help Desk at Toll-free: 1-866-793-2588.

For more information

If you have questions or would like more information about drinking water:

Disclaimer: This is a guide only and should not be relied on for compliance purposes. To be clear about your specific legal requirements, consult with your own lawyer and refer to the Safe Drinking Water Act, 2002.