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Ultraviolet Systems Questions & Answers
Should I shut my system off when I am not using it?
No, the UV system should be left on whether you are using the water or not.
The lamps age regardless of the amount of the water drawn through the system. By
leaving the unit on, you will eliminate the potential problem of having
contamination pass through the system while the unit is off.
Do I need to disinfect my municipal water supply?
Our municipalities work very hard to provide safe, disinfected water for their customers. This is quite evident when you consider the difficulties involved in providing safe drinking water through a vast distribution network. If you use water that comes from a municipal water supply and wish to provide your family with an added "peace of mind", then we believe a UV system acts as an inexpensive insurance policy against the possibility of drinking bacteriologically contaminated water.
Why do I need to disinfect my water supply?
Disinfection is recommended for all water supplies that are not protected by a municipal water source (ex. A private well). Unfortunately, due to the uncertainties that exist with our current water supplies, we can no longer rely on the fact that our water supplies 'may be safe'. By providing your own disinfection, you are taking the responsibility of ensuring the safety of your water supply for you and your family.
How does the UV light actually kill microorganisms?
UV does not kill microorganisms like chlorine does, but instead UV
inactivates them. UV light at a specific wavelength of 254 nm is readily
absorbed by the genetic material of microorganisms. The DNA strand is coded with
a specific sequence of something called base pairs. The sequence of these base
pairs codes for certain characteristics. UV light at 254 nm is readily absorbed
at the point on the microorganism's DNA strand which codes for reproduction. A
microorganism that cannot reproduce, cannot make colonies and therefore cannot
infect when consumed. In other words, the microorganisms have been sterilized or
neutered. They will eventually die off.
Does UV inactivate Cryptosporidium (Beaver fever) and Giardia?
Cryptosporidium and Giardia are what is called a protozoan cyst. Protozoa can
be described as microscopic, single celled microorganisms which live in water
and are quite a bit larger in comparison to other microbes. The majority of
protozoan cysts are parasitic. Both Cryptosporidium and Giardia are parasitic.
These organisms are in a dormant phase when in water but when they enter a host
(being any kind of mammal) they release colonies and begin to breed, ultimately
causing severe diarrhea and dehydration over a prolonged period of time.
Will a UV system kill all microorganisms in my water?
All Sterilight systems are rated for a 4-log inactivation of bacteria,
viruses and protozoan cysts under specific conditions. This rating is at a
specific flow rate, and water quality. It is a good idea to have your water
microbiologically tested prior to installing a UV system. We do suggest that if
your water has bacteria counts in excess of 1000 CFU/10 mL that you do a bit of
research with regards to what could be causing such high bacteria counts and
that you oversize your UV in order to ensure a high UV dose being delivered to
your water supply.
Is UV effective against E. coli?
Yes, E. coli requires a UV dose of between 6 -10 mJ/cm² to achieve a 4-log inactivation. This is well within the capabilities of Sterilight UV systems.
How do I clean the quartz sleeve?
If the quartz becomes stained, remove the sleeve from the reactor chamber and
clean the OUTSIDE with a commercially available scale remover, such as Lime-Away
or CLR. If the inside of the quartz sleeve does become wet, ensure that it is
thoroughly dried before putting the Sterilight system back together.
My lamp is still glowing blue; do I still need to replace it?
The UV light that is inactivating microorganisms in water is non-visible light, therefore the blue light that you see coming off a UV lamp is not what's doing the work. A UV lamp can be described as a low pressure mercury vapor lamp, which means it fires via mercury vapor. Over the course of a year that mercury is being used up resulting in a slight decrease of UV intensity. At the end of one year a Sterilight UV lamp has decreased in it's intensity by approximately 20%. We strongly recommend that UV lamps be changed on an annual basis.
What is recommended maintenance for a UV System?
Sterilight UV systems require the lamp to be changed on an annual basis
(provide they are not installed in a seasonal home). It is suggested that the
quartz sleeve be cleaned during the lamp change provided the home is supplied
with high quality water (no iron, hardness etc.) otherwise the sleeve should be
maintained on a regular basis.
Is UV light harmful?
You never want to expose your skin or eyes to the light from a UV system. UV
light is non-visible however it can be harmful, similar to the harmful effects
of UV light from the sun. UV lamps can actually cause a severe sunburn-like
effect if skin is exposed for long periods of time.
What does "log inactivation" mean?
Log inactivation is the inactivation of microorganisms on a logarithmic scale. Microorganisms must be considered on a logarithmic scale due to their high numbers.
What is UV dose?
UV dose is the energy that is coming off the UV lamp over a specific time
period. Therefore, UV dose (or fluence) is a product of UV intensity and time.
Dose is usually measured in milli joules per square centimeter. Each Sterilight
system is rated to disinfect your water at specific flowrate, under specific
water quality conditions to give a UV dose of 30 mJ/cm2 at the end of the lamp
life (which is one year).
What is UV light?
UV light is part of the electromagnetic spectrum, shining at a specific
wavelength.
Will UV change the taste and/or odor of my water?
No. With chemical disinfection, such as chlorination, the taste and odor of
your water will change (depending on chlorine levels water can smell and taste
of bleach) and disinfection by-products will be produced. A few examples of
chemical disinfection by-products (DBP) are trihalomethanes and haloacetic acid.
Both of these DBP's can be carcinogenic when ingested at high levels. The pH and
conductivity of drinking water also changes when chlorine is added.
I have colour in my water causing a low UVT, how do I remove it?
If you have high colour in your water it is most likely a concentration of
tannins. High tannin levels are found in most surface water supplies and some
groundwater or simply in waters where large quantities of vegetation have
decayed. Unfortunately tannins cannot simply be removed from water by a physical
means of filtration.
What is UVT?
UV transmittance at 254 nm (which is the wavelength of light that UV lamps
operate at) is a measure of the fraction of incident light transmitted through
the water column. The UV transmittance is the ratio of the light entering the
water to that exiting the water. The UVT is usually reported for a pathlength of
1 cm. As UV absorbance increases, the UV transmittance decreases (USEPA UVDGM
2003).
Does my water require pretreatment before my UV?
Yes, you must have your water tested prior to installing a UV systems. Many
people feel that if they can fill a glass with water and the water looks clear
then that must mean that it is. This is not true. There is more to water than
what the naked eye can see. Water flowing through a UV system needs to be free
from hardness, iron, turbidity, manganese and color (which can be called
tannins). The following is what R-Can recommends for the Sterilight UV systems:
How do I disinfect water lines in my home?
A UV system is there to protect your water from pathogenic microorganisms,
BUT there is the potential for harmful microorganisms to already be present in
the water lines. The water lines then need to be disinfected upon installation
of the UV system.
What is a solenoid valve and can I hook one up to a UV System?
A solenoid valve is an electrically-activated mechanical valve that opens and closes when power is applied to it. This kind of valve can be installed and wired into a Sterilight system which is monitored. If the UV intensity were to drop below the recommended level the solenoid would then be activated and automatically shut down the flow of water. This will keep contaminated water from getting through the UV system. A solenoid can be hooked up to a Sterilight system either by dry contacts (the Platinum, SUV and SUVAM systems all come equipped with dry contacts), or directly into the Sterilight system (Silver and GOLD series can be hooked up directly to a solenoid; outside power does NOT need to be brought to the solenoid).
Where do I install UV in relation to other treatment equipment?
The UV must be the very LAST piece of water treatment equipment.
Will a UV system restrict my water pressure?
No, Sterilight systems are designed with inlet/outlet ports correctly sized for the specific application. As an example, the 8 USGPM system comes with 3/4" ports. The typical pressure drop on this system would be 2-3 psi.
Will UV change the taste and/or odor of my water?
No. With chemical disinfection, such as chlorination, the taste and odor of
your water will change (depending on chlorine levels water can smell and taste
of bleach) and disinfection by-products will be produced. A few examples of
chemical disinfection by-products (DBP) are trihalomethanes and haloacetic acid.
Both of these DBP's can be carcinogenic when ingested at high levels. The pH and
conductivity of drinking water also changes when chlorine is added.
What UV dose is considered sufficient to remove viruses from water supply? I see your Sterilight units and/or the US industry standard dose = rated at 30mJ/cm2 at EOL. I can't find the 'compliance page' that is referred to in your Q&A "What is UV dose".
From the EPA Ultraviolet Disinfection Guidance Manual
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