What is UV treatment?
The UV treatment process uses ultraviolet (UV) light to degrade the DNA of organisms in your water. DNA is the instruction manual for the organism that tells it how to function and reproduce. With those instructions damaged the organism is rendered harmless, preventing infection and disease normally caused by the organism.
Do I need UV treatment?
Any homes that have tested positive for bacteriological contamination (including E. coli or other coliform bacteria) should implement UV treatment as soon as possible to prevent sickness and infection that can result from using untreated water. Any home on well water can benefit from a UV treatment system, as a negative bacteria test just means there is currently no bacteria but is no guarantee that bacteria will not be present in the future. Most homes on city water will not benefit from UV treatment since city water is typically treated for bacteria with chlorine or similar treatment, but for those who like to be overly cautious or those who live in cities that have frequent contamination warnings it would not hurt to have one.
**Please note: If you have iron bacteria, UV systems will not effectively treat it.
What size of UV system do I need?
UV systems are sized according to the number of gallons per minute (GPM) they can treat. If a system shows a range flow rates or multiple flow rates, those are for the different dosing standards. To ensure full treatment it is recommended to use the lower number for sizing, as this will meet the NSF dosing standard to ensure the highest quality treatment.
A simple way to test your flow rate is to fill a bucket (5 gallon is a common size) at the install point (typically where water enters the home, and right after the pressure tank on well systems), and time how long it takes to fill up. If a direct reading from the install point is not possible, measure the largest spigot (such as a garden spigot) as close to the install point as possible. Divide 60 by the time it takes to fill the bucket (in seconds), then multiply by the size of the bucket (in gallons) to get your GPM. Example: If it takes 37.5 seconds to fill a 5 gallon bucket –
Your flow rate would be 8 GPM.
Once you have your flow rate, you will want to find a system that will treat it OR HIGHER. Remember to use the lower number for sizing to ensure the best treatment. For example, looking at the Sterilight VH410 system, it is rated for 14-18 GPM so you would only want to use it if your maximum flow rate was 14 GPM or less.
In some cases your available flow rate may far outweigh your actual usage capacity. If you have a GPM flow rate but are only a single person in 1 bathroom home it is highly unlikely that you will ever actually use 20 GPM. In these cases you can use a smaller system, though it is recommended to use it in conjunction with a flow restrictor to ensure you don’t accidentally pull more than the system can handle.