Using ultraviolet (UV) disinfection on drinking water systems
Find information on UV disinfection units for drinking water systems serving a non-municipal year-round residential system or designated facility.
On this page Skip this page navigation
Ultraviolet disinfection is a well-established method for achieving adequate disinfection for drinking water supplies. UV disinfection is a process intended to inactivate human pathogens such as viruses, bacteria and protozoa that are potentially present in raw water before receiving proper disinfection. As water passes through the UV unit, an ultraviolet range of light inactivates these human pathogens.
Maintain your UV system
Maintenance of 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
You must maintain your UV unit according to:
- your Engineering Evaluation Report (EER) – if you have an EER, it should be given priority when determining maintenance tasks
- the manufacturer’s manual
- a ministry approval
Who can maintain your system
Proper day-to-day operation maintenance of your drinking water system is the responsibility of your certified operator or trained person.
For more information on operator certification:
- visit the drinking water operations: training and certification page
- contact the Ontario Water Wastewater Certification Office by calling
- read Ontario Regulation 128/04 – Certification of Drinking-Water System Operators and Water Quality Analysts
Typical maintenance activities
You should always be aware of your own system’s maintenance requirements.
Some typical maintenance activities for UV systems include:
- changing your UV bulb: UV bulbs should be changed according to your requirements after a certain number of hours of use. How many hours will depend on the quality of your raw water. Most UV units feature an audible or visual alarm to warn users that the bulb needs replacement.
- cleaning your quartz sleeve: a cloudy quartz sleeve lowers the UV system’s effectiveness to disinfect. To ensure proper disinfection the quartz sleeve should be inspected and cleaned regularly. A good rule of thumb is to clean the sleeve monthly but frequency may vary depending on raw water characteristics. Some units include automatic sleeve cleaning. Check your manufacturer’s instructions to confirm if your unit has this feature.
- confirming your UV alarm and/or automatic shut-off is working: The alarm and/or automatic shutoff should be inspected and tested on a regular basis. A functional automatic shut-off stops the flow of water in the event of an equipment malfunction, loss of power or improper disinfection. An audible alarm immediately alerts the operator allowing them to monitor the system and take the appropriate actions. This is important to ensure no improperly disinfected water is directed to your consumers. Not all UV units include auto shut-off as a standard feature. On many models an auto shut-off valve is an optional add-on. Check with the manufacturer to find out if your unit has an auto shut off valve and if not, if the unit can be upgraded to add this important safety feature.
- cleaning your sensor: To ensure proper disinfection is occurring, the sensor should be calibrated, cleaned and inspected according to your requirements. If cleaning is not done regularly, the sensor will inaccurately read incoming UV light and may jeopardize the safety of your water.
Documenting your maintenance
The operator must record any UV equipment maintenance, checks and adjustments in a log book that can be inspected by a water inspector from the Ministry of the Environment and Climate Change. When recording these activities the operator should make note of the activity, date, time and the operator’s full name.
Upgrading your UV unit
A report must be submitted to the ministry if you are upgrading your UV unit.
For any changes to your drinking water system (e.g., contact information or upgrading your UV unit), complete a Drinking Water System Profile Information form and send via email within 10 days of the change.
If you have any questions about registration, call the Registration Help Desk at
When upgrading to a new UV unit, you must consult with an engineer specialized in water treatment to ensure that you are installing a UV unit that will properly disinfect your drinking water supply.
Your UV unit needs to have sensor and an automatic shut-off or alarm functions to meet regulatory requirements.
National Sanitation Foundation (NSF) 55 Class A Certified Units
The ministry recommends you use a UV unit that is NSF 55 A certified. These units are equipped with automatic shut-offs, sensors, flow restrictors, alarms and provide adequate disinfection of drinking water for your users. The owner’s manual or your EER would confirm if the UV unit is NSF certified.
Tips for automatic shut-off functions
An automatic shut-off is a device which is used to automatically stop or open water flow through an electrical switch. The device automatically stops the flow of water when the sensor has determined an inadequate level of treatment is being provided such as during a power outage or a deficiency in the effectiveness for the UV light to disinfect your drinking water.
Adding an additional locking device onto your shut-off will help to ensure that the shut-off is not positioned to manual. If the shut-off is in the manual position, there is a risk that the shut-off will not stop the flow of water if a problem occurs and that untreated water may flow to the users of your drinking water system.
Installing an alarm on the automatic shut-off will notify the system operator when a problem has occurred. This is so that the operator can attend to the problem promptly and ensure the automatic shut-off has fully engaged.
Report a problem
If your UV disinfection unit, automatic shut-off or alarm feature fails and the system has the potential of delivering improperly disinfected water to users of the system, it is considered that an adverse water quality incident has occurred and must be reported.
Your first step in the case of an adverse water quality incident is to make an immediate report (by telephone or in person) to all of the following:
- your local medical officer of health at the local public health unit, by speaking with someone in person or on the telephone
- the ministry’s Spills Action Centre (
Tel: 1-800-268-6060), open 24 hours a day and 365 days a year
- the operator of each designated facility served by your system (if applicable) by speaking with someone in person or on the telephone 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.
For full information about the subsequent steps you must take to report an adverse water quality incident, see the section on notifying authorities of adverse test results and other problems in the:
- guide for non-municipal year-round residential drinking water systems
- guide for drinking water systems serving designated facilities
For more information
Contact a local MOECC office and ask for your local drinking water inspector.
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.