UV Water Disinfection FAQ
- HOW LONG HAS UV WATER DISINFECTION BEEN IN USE?
- WHO SHOULD USE UV WATER DISINFECTION?
- HOW DOES UV DISINFECT WATER?
- WHAT IS UV DOSE?
- WHAT UV DOSE DO I REQUIRE?
- CAN I DO MY OWN INSTALLATION?
- WHAT ARE THE OPERATING COSTS OF A UV DISINFECTION SYSTEM?
- DOES THE UNIT NEED TO BE ON CONTINUOUSLY?
- WHERE DO I INSTALL THE UV DISINFECTION UNIT?
- CAN I INSTALL A BYPASS VALVE?
- I AM INSTALLING THE UNIT IN A COTTAGE?
- I HAVE MUNICIPAL WATER – DO I NEED UV DISINFECTION?
- IS WATER PRE-TREATMENT REQUIRED?
- HOW LONG DOES THE UV LAMP LAST?
- DO I NEED TO REGULARLY TEST MY WATER?
HOW LONG HAS UV WATER DISINFECTION BEEN IN USE?
The first recorded use of UV water disinfection was in 1906 with a municipal installation in Anon, France. Residential application of the process was given renewed interest during the 1950’s and has been growing at a rapid rate ever since. The technological challenges and uncertainties faced by the early pioneers have been resolved. Today’s UV equipment is not only competitively priced, but offers low maintenance and low operating costs compared to other disinfection methods. It is the disinfection method of choice for most residential applications.
WHO SHOULD USE UV WATER DISINFECTION?
Any one who receives their water from a private well or surface water needs to disinfect. In many areas we can no longer assume the safety of our water source with the ever-increasing effects of agriculture and industry.
HOW DOES UV DISINFECT WATER?
When disease causing microorganisms are exposed to UV light, their DNA is disrupted, disabling the microorganism’s ability to replicate and cause illness.
WHAT IS UV DOSE?
UV dose is the function of both the intensity of the UV radiation and the length of time the water is exposed to the UV radiation. UV dose is expressed in millijoules(mJ)/centimeter squared (cm2)
WHAT UV DOSE DO I REQUIRE?
UV disinfection equipment is being manufactured to a number of different dose standards; it is important to know the dose being used when flow rates are specified.
The oldest standard still in use is the US Department of Health standard, which recommends a dose of 16mj/cm2. This dose is still considered acceptable for applications where the UV disinfection device is used to treat for nuisance organisms that colonize filters and water softeners when used with municipal water sources.
For many years the industry used a standard of 30mJ/cm2 for primary disinfection. More recently, leading authorities (including the US EPA and NSF) have adopted a dose of 40mJ/cm2 for primary water disinfection. We highly recommend the 40mJ/cm2 for all installations where the water source is a private well or surface water, and a dose of 30mJ/cm2 for all applications with municipal water supply.
CAN I DO MY OWN INSTALLATION?
Where local regulations allow and you have basic plumbing skills, UVDynamics equipment can be DIY installed. Please review the downloadable PDF format installation instructions for more detailed information.
WHAT ARE THE OPERATING COSTS OF A UV DISINFECTION SYSTEM?
A standard residential UV system uses, on average, 20 cents a day of electricity. Consumables are minimal – a new UV lamp annually to maintain the UV dose, and a recommended new quartz sleeve every 3 years.
DOES THE UNIT NEED TO BE ON CONTINUOUSLY?
Yes, the UV lamp needs to operate for several minutes to reach full UV output – it cannot be used on demand. Excessive on/off cycling of the UV lamp will greatly reduce its life expectancy. Additionally, by having the unit on continuously, the chance that untreated water will be consumed is minimized.
WHERE DO I INSTALL THE UV DISINFECTION UNIT?
UV disinfection equipment should always be the last stage of any water treatment system, and should be installed so that both the cold water distribution system and the hot water heater receive disinfected water.
CAN I INSTALL A BYPASS VALVE?
Yes, if desired a bypass valve can be installed. The bypass valve must stay closed during normal operation. A leaking bypass valve will result in untreated water entering the plumbing distribution system.
I AM INSTALLING THE UNIT IN A COTTAGE – CAN I TURN IT OFF WHEN I’M NOT THERE?
UV disinfection is becoming very popular for cottages and summer residences. If your UV system is not going to be in use for several months, you can disconnect it from the AC power source during absences. Where freezing temperatures are possible, you must completely drain the disinfection chamber (and any other water treatment equipment). When used in this manner, the quartz sleeve should be cleaned annually and the UV lamp should be replaced after two years, regardless of hours of use. We do not recommend disconnecting the unit from the AC power source in situations where the cottage will be used on a regular basis - e.g. every weekend.
I HAVE MUNICIPAL WATER – DO I NEED UV DISINFECTION?
The majority of municipal water providers do an excellent job of meeting their licensing requirements. However, aging infrastructure and decreased budgets have resulted in more frequent boil water advisories, even in urban areas. By the time a boil water advisory has been issued, residents have often already ingested contaminated water. Installing a UV disinfection system is an easy way to provide additional water supply security for yourself and your family, particularly immunocompromised individuals, seniors, and small children. Low operating costs and a lack of disinfection by-products makes UV disinfection an excellent choice for this type of scenario.
If you are using a whole house point of entry activated carbon filter to reduce chlorine and other contaminates, then the use of a UV water disinfection device after the activated carbon filter is highly recommended as micro-organisms are known to colonize in these filter media.
IS WATER PRE-TREATMENT REQUIRED?
Yes, water to be treated by a UV system must have pre-treatment; the level of pre-treatment required will depend on the quality of your input water. UV disinfection is a physical process and the microorganisms need to be exposed to a minimum level of UV energy for effective disinfection. To ensure low maintenance and reliable operation, input water must not contain any elements which significantly reduce the UV transmission of the water or form a deposit on the quartz sleeve. Both of these scenarios will lower the amount of UV light energy in the disinfection chamber, lowering the UV dose the system can achieve.
Water which meets the following minimum guidelines generally only requires an annual maintenance interval, consisting of lamp replacement and cleaning of the quartz sleeve.
Turbidity: < 1 NTU
Suspended Solids: < 10mg/L
Colour: None
Total Iron: < 0.3 mg/L
Manganese: < 0.05 mg/L
Hardness: < 7 gpg
If you are unsure as to whether your water source meets the required minimum standards, we suggest you have a sample of the water analyzed by a local water testing laboratory. As a minimum, the installation of a 5 micron pre-filter is required before all UV disinfection equipment. If your water needs pre-treatment in addition to the 5 micron pre-filter, we would suggest you consult with a local water treatment dealer who is familiar with water conditions in your area.
UV Transmission (UVT) is a measurement of how much UV light can shine through 1cm of water, expressed as a percentage from 1-100%. UV system doses are listed assuming a UVT level of 95%. If you input water has dramatically lower UVT levels, you will want to increase pre-treatment to raise the UVT, or oversize your UV system to compensate.
HOW LONG DOES THE UV LAMP LAST?
The output of a UV lamp decreases slowly with age, and has a useful life of 9000 hours. Beyond 9000 hours, the lamp output starts to degrade rapidly and disinfection performance will be suspect. UVDynamics disinfection units are designed to provide the specified dose at the end of the useful lamp life. The integral lamp change reminder alarm will prompt you when it is time to change the lamp, beginning with a 4 week warning period before full lamp expiry. Operating the lamp beyond 9000 hours will result in reduced disinfection performance.
DO I NEED TO REGULARLY TEST MY WATER?
Yes, even with a UV disinfection unit installed, regular water testing is still required to verify the safety of your entire water distribution system.