UV Water Purification System Buyer's Guide

UV Buyers Guide for Purchasing UV Water Treatment System

What to Know Before Buying a UV Water Sterilizer

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Prior to purchasing an ultraviolet water disinfection system, it's important to understand that UV light destroys 99.99% of waterborne microbes such as viruses and bacteria. But UV does not address contaminants such as heavy metals, salts, chlorine, pesticides, arsenic, rust, petroleum products or pharmaceuticals. Other filtration methods or an integrated UV system should be employed with UV to ensure that all contaminants are removed from the water.

Take time to educate yourself about ultraviolet water purification to make sure UV technology is the right solution for your water treatment needs.

How to Choose the Right Ultraviolet Sterilizer

In order to provide peace of mind and daily protection from microbiological contamination of your water, it's important to select the right size ultraviolet light treatment system.

UV System Flow Rates: UV water purifiers measure water flow rates in “gallons per minute” or GPM, indicating how much water can flow through the system.

Since water may not be effectively treated if the system cannot handle the flow rates for your home, we tell customers that it's better to oversize a UV water treatment system rather than under size.

Expert Tip:
Number of Bathrooms in Home Can Determine Needed Flow Rate for UV Light Disinfection System

For whole-home applications, a simple way to determine what size UV system is needed, is by assessing the number of bathrooms in the house. Here's a flowrate guide for whole-home UV sterilizers.

6 gallons per minute flow rate.
If you have one bathroom in your home, you'll need a UV water sterilizer with at least 6 gpm flow rate, such as the Luminor Blackcomb 4.1 LB4-061 UV system.

9 gallons per minute flow rate.
If you have two bathrooms in your home, you'll need a UV water sterilizer with at least 9 gpm flow rate, such as the Viqua VH200 UV System.

12 gallons per minute flow rate.
If you have three bathrooms in your home, you'll need a UV water sterilizer with at least 12 gpm flow rate, such as the Viqua 650694-R D4 UV System.

15 gallons per minute flow rate.
If you have four bathrooms in your home, you'll need a UV water sterilizer with at least 15 gpm flow rate, such as the Luminor Blackcomb 6.1 LB6-151 UV System with Sensor.

18 gallons per minute flow rate.
If you have five bathrooms in your home, you'll need a UV water sterilizer with at least 18 gpm flow rate, such as the Viqua VH410 UV System.

Flow rates for commercial applications are determined with a variety of other factors. Please contact us for more information.

Selecting the Correct UV Dose for Your System

The amount of UV energy from the lamp to the water as it flows through the system is the “UV dose” expressed as millijoule per square centimeter or mJ/cm2. E. Coli, Giardia, and Cryptosporidium typically require a UV dose of at least 10 mJ/cm2 to become inactivated.

The typical whole-house UV light system has flow rates of 30 mJ/cm2, which is sufficient for most residential applications. Flow rates for products with NSF Class “A” certification are rated at 40 mJ/cm2. NSF Class “A” certified systems are typically only used for specific commercial applications.

If you’re on a private well, it’s especially important to know exactly what’s in your water. Private well water is not regulated by municipalities. It is therefore recommended that you find a lab that can provide a water analysis services including testing for E.Coli, bacteria, viruses, and the contaminants listed above.

What Are the Space Requirements for UV Water Disinfection System?

The footprint of UV disinfection systems is generally quite small. That's why they're easy to install in most applications. If a water softener and other pretreatment is installed with a UV filtration system, then more space will be needed. UV systems are typically installed vertically, but can also be installed horizontally.

When determining the space needed for installing a UV system, make sure to allow at least double the size of the UV system dimensions so that there is plenty of room for replacing the lamp and sleeve. Also, consider the space needed for any pre-filtration systems.

Installation NOTE: When you have multiple filters such as a water softener or "Big Blue" water filter in place, the UV system is usually installed last in the lineup.  

More compact UV systems often use a brighter lamp and may be slightly more expensive, but one style is not more effective at treating water than the other.

Diagram of a Whole House size UV Water Purification system

Optional Features Available: Most UV systems come standard with an end-of-life countdown display indicating how many days remain until the lamp needs to be replaced. Other systems come with controllers that have LED lights indicating proper function of different system components. Some newer systems come with touch screen displays. However, UV systems can come with a variety of options and add-ons. The most common option added by homeowners is the sensor. Commercial applications are more likely to add a solenoid shutoff valve and flow meter.

Are Prefilters Needed for a UV Water Sterilizer?

Prefilters can protect your UV light disinfection system & improve UV efficacy.

If water is cloudy, a pre-filter should be used. Sediment found in city and well water can be large enough to create shadows for bacteria to hide behind and thus, hinder the systems' ability to effectively treat water. UV manufacturers highly recommend a pre-sediment filter be installed before the UV system to ensure proper water treatment.

One top-selling options is an "integrated system" that filters out sediment, grit, sand, rust, and dirt before the water enters the UV chamber. For example, the VIQUA IHS22-D4 is a pre-assembled high-capacity unit that combines the popular VIQUA D4 UV sterilizer with sediment and carbon prefilters.

Do You Have Hard Water? 
Hard water can cause scale build-up on the UV lamp which decreases the efficacy of the ultraviolet process. "Hard water" means the water coming into your home is high in calcium or magnesium. Hard water should be treated with a water softener before the water enters the UV chamber. If left untreated, these minerals can coat the quartz sleeve and impede the UV disinfection process. 

Quality of Water Before the UV System
To keep a UV system functioning at peak performance, it’s important to know what contaminants are in your water before installing a UV water filter system. To understand what's in your water, refer to the Consumer Confidence Report (CCR) available from your water supplier July 1 each year. If you're on a private well water, we highly recommend testing your water. Learn more about water testing from the EPA website.

Because high levels of hardness, iron, and sediment may not allow the UV system to properly treat the water, we recommend the incoming water to the UV system meet the following parameters:

    • Hardness < 7 grains per gallon
    • Iron < 0.3 parts per million
    • Manganese < 0.05 parts per million
    • Turbidity < 1 NTU
    • Tannins < 0.1 parts per million
    • UV Transmittance > 75%

If your water does not meet the above parameters before entering the UV chamber, then pre-treatment equipment may be necessary.

What Does a UV Water Filter Remove?

Overall, UV water treatment is an outstanding way to meet your water purification needs. A UV system is primarily used for removing viruses, bacteria and other biological contaminants found in water.

Biological Contaminants Found in Water


E. coli


hepatitis A







typhoid Fever






How to Remove Bacteria from Well Water

If you’re on a private well, it’s important to know exactly what’s in your well water. Because private wells are not regulated by municipalities, contamination in the water can go undetected. That’s why having a sampling of your water tested by a lab is so important, and really the best way to understand what’s in your water, although bacteria levels in well water can fluctuate due to many external factors such as flooding, spring runoff or even simply a heavy rainstorm. If your well is older, there are also many ways that surface contamination could affect your drinking water.

Many well owners "shock their wells" with chlorine to address bacteria issues.

Well Shocking means high levels of chlorine are introduced into the water source and plumbing system for a temporary period in order to kill bacteria. While shock chlorination is a relatively economical, "quick fix" to treat bacteria in a well, the solution is only temporary and not always reliable. It also requires re-testing, which can become very expensive.

As an alternative, UV Disinfection can protect the whole home from the threat of illness-causing microbes in water.

  • UV provides a long-term reliable method of treating well water by running the water over a UV light that kills bacteria and viruses.
  • This process of exposing water to UV light is simple but effective, and destroys 99.99 percent of harmful microorganisms, including some that are chlorine resistant (such as Cryptosporidium and some forms of Giardia).
  • No chemicals added with UV disinfection, so there is no change to the taste or odor of your water. And, with UV, you don’t have to handle noxious chemicals, monitor the chemicals, or worry that someone in your home will become sick.
  • Well Treatment with a UV Disinfection system (like the Viqua IHS12-D4) provides peace of mind that your well water is being disinfected continuously, 24/7.  

We highly recommend you read this article on Well Water Contamination by Viqua.

Shocking a Well vs. UV Light Disinfection

What Is the Difference Between UV Disinfection and Chemical Well Shocking?

Well Shocking w/ Chlorine UV Disinfection
Temporary quick fix

Long-term, effective solution that destroys 99.99% bacteria, viruses, and cysts

Essentially trouble-free, annual maintenance of UV lamp change & sleeve clean

Works 24/7 to consistently keep water safe from illness-causing microbes

Environmentally friendly - no disinfection by products and no wasted water

Indicator alarm sounds if water is not being treated

No harsh chemicals that can damage skin

No damage to well casings & pump fittings from chemicals

No dangerous gas (oxidation of organics can generate THMs, a harmful gas)

Taste and odor of water not affected

Top-Selling UV Water Filter Systems

How to Filter Water from Rainwater Catchment

Rainwater harvesting is becoming increasingly popular. It’s a great way to lower utility bills and help the environment. But it’s important to understand that just because water came from the sky, doesn’t necessarily mean the water is clean or safe to drink.

Rain barrels may collect more than water, such as animal excrement, leaves and dirt particles. And water sitting in storage drum is also susceptible to bacterial growth.

For these reasons, collected rainwater should be treated prior to consumption. This way, you can best guard against becoming sick.

UV light disinfection is an effective way to treat harvested rainwater to guard against waterborne bacteria, viruses, and pathogenic disease-causing microorganisms such as Cryptosporidium and Giardia.

UV light filters can purify your rainwater

Considerations Before Purchasing UV for Rainwater Harvesting

Turbidity in water which often causes cloudiness, and should be a consideration when treating harvested rainwater. Water collected from roofs and gutters, may contain leaves, roofing debris, and dirt particles. These suspended solids make a prefilter necessary prior to the ultraviolet purification process, as UV will not work effectively if turbidity has not been properly addressed.

We highly recommend an integrated UV system such as the Viqua IHS22-D4 in rainwater harvesting applications.

Ultraviolet Technical Tips

How to Change a UV Lamp

Instructions on how to replace a UV water sterilizer lamp yourself, including step-by-step instructions and video.
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How to Clean a UV Sleeve

Cleaning the UV sleeve in an ultraviolet water sterilizer system is crucial to maintain optimal performance. Learn how to properly clean a UV sleeve.
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How to Maintain a UV System

Tips for proper maintenance of a UV water disinfection system. Find solutions, UV system troubleshooting tips and more.
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