Posted by Jeff Wahl on 9/4/2024 to
UV System Education
What is an Ultraviolet (UV) Disinfection System?
An ultraviolet disinfection system is a water treatment system installed either at the kitchen sink or where the water enters the house. The purpose of UV disinfection is the inactivation of harmful bacteria, viruses and dangerous parasitic protozoa such as cryptosporidium and giardia occurring at the point of contact between UV rays and water inside of a stainless steel chamber.
The ultraviolet lamp / bulb is the source of the UV ray and radiates 360 degrees through a Quartz Sleeve which protects the lamp from coming in contact with water. The benefit of this type of disinfection process is the instant neutralization of microorganisms preventing them from causing any harm. The process adds no by-products to the water.
Today’s market for UV Systems is diverse and can often be challenging for an average homeowner to understand the water quality, maintenance and operational requirements to keep the water safe.
Considerations when Choosing a UV System
- Gallon Per Minute Flow Rate
- Size of the Building and Piping
- Water Quality Requirements
- Proper Pre-Treatment Achieving 5 Microns
- Annual Ultraviolet Lamp Replacements
- Clarity of the Quartz Sleeve
- Proper Plumbing Disinfection
- Where the UV is to be Located?
- Understanding UV Transmittance
- Manual Plumbing Bypass
- What is Sediment Shadowing?
- What to do During a Hydro Outage?
The Importance of UV System Maintenance
Every ultraviolet disinfection system has maintenance requirements such as lamp / bulb replacements, quartz sleeve cleaning, O-Ring replacements and plumbing disinfection of piping. Understanding how a UV system works is important to ensure the bacteriological safety of the water. Ultraviolet lamps require either an annual or bi-annual change and most systems have a reminder feature to ensure that maintenance is completed when required. 5 micron sediment removal is important to allow the the UV ray in the system to properly contact bacteria as the water flows through the UV chamber in route to the building. Cleaning the quartz sleeve frequently and replacing it when signs of calcification, etching, pitting or discoloration appear is imperative for the UV disinfection process to occur.
Understanding the Importance of Quartz Sleeves
A UV Lamp emits 360 degree rays through the quartz sleeve within the UV chamber to disinfect water. Water quality can have an impact on your sleeve and result in it becoming fouled with dirt, scaling, stains or scratches. Coarse sediment can result in pitting or etching of the quartz sleeve exterior surface. Fouling and etching can refract the UV rays and prevent them from reaching the water in the proper strength to disinfect properly. In some cases the sleeve is severely fouled with contaminants such as iron or sulphur and the rays do not reach the water at all. This prevents disinfection of the water and there are no warning or indicators indicated by most residential UV systems.
Cleaning, Handling and Care
Residual oils from skin will remain on the outer surface of the sleeve. Gloves should be worn at all times when handling quartz sleeves to prevent transfer of oils to the exterior of the sleeve. Care should also be taken not to allow any water into the center of the sleeve. You should never have to clean the inside of the sleeve as the water flows on the outside. Cracks, especially at the top of the sleeve are a potential flood risk and it should be replaced immediately. Clean using a soft pad with a commercially available scale remover such as Lime-Away or CLR and always ensure that you do not allow cleaner or water to enter the center of the sleeve.
Cleaning Frequency
Proper pre-treatment of water for hardness, scaling, iron, sulphur or particulate will result in less frequent cleaning. Be sure to clean the sleeve with every UV lamp replacement. After your system is installed, it is a good rule to check the sleeve for fouling after three months operation. If you are noticing discoloration, scaling or coating of the surface, it will need to be cleaned more frequently. If this is the case, you should have your water tested to determine the source of the problem and identify what is required to prevent it from occurring. If you have to clean your sleeve on a regular basis, it is not working properly.
Replacement Intervals
Manufacturers recommend replacing the sleeve every 24 to 36 months depending on water quality. Based on manufacturer's recommendations, a good practice is for 24 month replacements. This will help to provide a clear path through the sleeve for UV rays to disinfect water. It is important to note that frequent cleaning can leave residuals behind, and it is recommended to follow your manufacturer’s suggested change intervals.
Testing the Water Prior to Installation
All manufacturers indicate the water quality operating requirements for their systems which are designed to ensure that the system operates properly. Water quality can cause fouling of the UV quartz sleeve which prevents the UV Ray from coming into proper contact with the water properly. Most UV Systems have no warning alarm or indicator to notify when quartz sleeves are fouled. Water should be treated for sediment, hardness, clarity, iron, sulphur, tannins and be conducted prior to installing any UV system.
| Element | Operating Value | Information | Impact on UV System |
| Iron (Fe) | <0.3 ppm / mg/L | Three types: Ferric, Ferrous or Bacterial | Coats the outside of the sleeve with orange particulate or scaling |
| Hydrogen Sulphide Gas (H2S) | <0.3 ppm / mg/L | Two types: Gas or Bacteria | Coats the outside of the quartz sleeve with grey to black or slimy adherence |
| Water Hardness | <7 GPG / ppm | Dissolved Calcium & Magnesium in water | Coats the outside of the quartz sleeve with white scale deposits |
| Tannin / Lignin | <0.1 ppm / mg/L | Yellow, Reddish or Brown coloured water from vegetation sources | Interfere with UV's ability to penetrate into the water due to the tannins absorption capabilities |
| Manganese | <0.5 ppm / mg/L | Mineral found naturally in the environment | Coats the outside of the quartz sleeve with a dark brown or black adherence |
| Turbidity | <1 NTU | Refers to how clear the water is. Total suspended solids (TSS) | Interfere with UV's ability to penetrate into the water due to water clarity |
Consideration for the UV System O-Ring (s)
To ensure that there is a water tight seal and prevent water from entering the sleeve or escaping the UV chamber, an O-ring is used. This is located at the top of the open end of the sleeve or at both ends if it is a double ended open sleeve. The O-ring(s) should be replaced annually with every UV lamp replacement. Heat generated from the normal operation of UV systems can deteriorate O-rings over prolonged periods of time, causing lamp failures from water entering the sleeve or flooding from water leaving the UV chamber. O-rings are typically shipped in the packaging for all new quartz sleeves and UV lamps.
Tips & TricksDo not use any vaseline or silicone based lubricants on the O-ring.
Discard all old or used O-rings are they can dry out or become cracked.
Keep a spare set of O-rings on hand in case of emergencies.
The Implications of Power Outages
Rural areas experience power outages on a more frequent basis than their urban counterparts. Often people will turn on taps or flush toilets during an outage and inadvertently cross contaminate their water piping without ever knowing it. This action can result in water cross contamination with very little water passing through the UV.
As water passes through a non-operational UV, the bacteria does as well. When power is restored, most homeowners assume that everything is okay because the UV continues to function. This may not be the case, as bacteria have the opportunity to replicate on the other side of the operating UV light. Simply turning the UV system back on does not guarantee the water is bacteria free, as there is no residual disinfecting occurring in the pipes. Once cross contamination has occurred, a proper pipe disinfection including the hot water tank should be performed.
This scenario is plausible as the pressure tank associated with many rural water sources will provide 4 to 20 gallons of water after the power goes out and allow water to pass through the UV System untreated. While not as common in rural areas close to larger cities, it can be a common occurrence in rural areas with minimal development and large areas for power lines to travel before entering homes.
There is another scenario involving power which is seen many times in the field of water treatment. Many people simply turn on the UV system when they feel bacteria may be present in the water and turn it off again when they feel there is no bacteria. It is not possible to know without proper testing. Bacteria can be present in a water source through all of the seasons, 365 days a year.
When the Power Goes Out - Do Not Use the Water
Manual Plumbing BypassA plumbing bypass is often installed to allow water to “go around” the UV system. It is usually installed for emergency purposes, such as the UV system leaking.
It is also installed to allow for uninterrupted water usage during routine maintenance of the UV system when service is required to replace the ultra violet lamp and quartz sleeve.
The use of a bypass can lead to water cross contamination as bacteria makes its way into the plumbing system. Once power is restored and the bypass closed, there is the potential for bacteria to be present in the hot or cold water piping located after the UV system. When this occurs, the water piping and fixtures will require disinfection as bacteria can be present once the UV system is turned back on.
Caution when Using a Bypass ValveSometimes a bypass valve can be left in the open position resulting in water never entering the UV chamber at all despite the system being on and functioning properly.
What is Sediment Shadowing?
All manufacturers recommend achieving 5 micron sediment filtration. This is to ensure that there is the proper path for the UV ray to reach bacteria flowing through the UV chamber. When particles of sediment are larger than 5 microns in size they can act as a “shield” and prevent the UV Ray from coming into contact with microbes. Once sediment is removed, the UV ray can “see” the bacteria in the water properly and disinfection can occur.
5 Micron Sediment Filtration is Required for All UV Systems
If you are using a UV light for bacterial disinfection, it is important to understand how it operates and properly pre treat the incoming water source. If you are unsure about your water quality or have questions, consult a certified water treatment professional who can provide you with the necessary information to ensure that your UV system is capable of disinfecting the water in your home or cottage.
Volume 7 – Issue 4 Wahl H2O - Water Awareness
Copyright 2024 Jeff Wahl – Wahl Water | All Rights Reserved
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