Education - Cross Contamination

What is Water Cross Contamination and How Does it Work?
An Ultra Violet Light provides bacterial disinfection for a water supply assuming that the system remains operational the UV Ray can properly "see" the water inside of the UV chamber. There are a number of factors that can present a risk to water quality and result in a contamination of the water supply downstream of the UV System.
Hydro Interruption - Water Flow - Hydro Restored
There is a risk when the hydro goes out as quite often people will turn on taps or flush toilets during an outage with the pressure remaining in a pressure tank and inadvertently cross contaminate their plumbing without ever knowing it. Bacteria passes through the UV when it is not on and when power is restored the homeowner assumes that everything is okay because the UV is operational again. This may not be the case as bacteria have the opportunity to replicate on the other side of the operating UV Light.
Fouled Quartz Sleeve / Dome
Water Quality can have an impact on the ability to see through the Quartz Sleeve. For simplicity this can be illustrated using a common light bulb analogy. If you paint a light bulb orange and turn it on, there is power and the light is on but it will not shine very brightly. The same analogy applies for a Quartz Sleeve, if Iron (orange staining) exists in the water there can be a coating of the Quartz Sleeve and diminish the strength of the UV Ray. The same applies for Water Hardness (white scaling) and Sulphur (black film). Most UV Systems do not have a device to monitor the strength of the UV Ray and consumers may have an operational system with a fouled sleeve and bacteria passing through the system out into the home's water supply.
Sediment "Shadowing"
Turbid water (sediment) will also interfere with the UV Ray as microorganisms can “hide" in the particles and not be inactivated inside the chamber. E-Coli and Coliform Bacteria can "hitch" a ride through the UV System attached to a particle of sediment.