Spa Solutions
UV Water Treatment Gaining Ground

By Jeff Boynton

Spas are a favorite water pastime and are present in many recreational aquatic facilities. However, the warm water is also a breeding center for many water-borne microorganisms. And the warm water has more evaporation than drinking water, thereby making the halogen treatment more volatile. Today, ultraviolet water treatment for spas is gaining use as a valid alternative in recreational spa facilities as it adds nothing to the water while keeping it clean and improving air quality around the unit.

Recreational aquatic facilities are turning to UV water treatment not only because of local health requirements but also because of their ease of use, reduced chemical consumption, health advantages and environmentally friendly benefits. As UV treats the water that passes through the UV light chamber and does not add anything to the water such as ozone or chlorine gas, the resulting water treatment is not corrosive or damaging to the spa equipment. Since the total water volume of a spa is turned over in a relatively short period of time through the filtration and UV cycle, the warm spa water is frequently sanitized.

UV water treatment is based on using the power of germicidal light to disinfect the water thereby consuming less chemicals and allowing them to be more effective. UV-C eradicates microorganisms that pass through the UV light chamber, but it does not act as a residual. UV light technology only works on the water flowing through the light chamber; it does need chemical sanitizers, but only in low concentrations.

What Is UV?

More than 100 years ago European scientists from different countries discovered the top surface of lake water was sterile when exposed to sunlight. Investigation led to the discovery of ultraviolet light and to the invention of UV bulbs. UV light is situated in the electromagnetic spectrum between X-rays and visible light. UV light is split into four main categories, UV-A, UV-B, UV-C and Vacuum UV. The area between 240 and 280 nanometers (nm) is UV-C, commonly known as germicidal light. This is the UV light that is used to sanitize spas and hot tubs.

UV-C light has the ability to cause permanent damage to a wide variety of microorganisms in water. Certain species of microorganisms, such as Legionella and the news-making protozoa Cryptosporidium, are not completely sanitized with traditional disinfection techniques such as chlorine. UV-C light is not a biocide but disrupts the microorganisms' DNA, ensuring that organisms present in water are unable to replicate and remain inert. All germs, viruses, bacteria, etc., are thus de-activated and can no longer reproduce. Unlike other sanitation treatments, UV does not affect the taste, color or pH of the water being disinfected.

Choosing UV to Improve Water and Air Quality

We all know that spa water must be sanitized. Moreover, the warm water in spas must be treated with chemicals continuously in order to deactivate pathogenic microorganisms and to prevent the spread of waterborne illness. Unfortunately, chemicals such as bromine and chlorine react with organic and mineral compounds, resulting in harmful and smelly byproducts.

Ensuring good water chemistry is the key to maintaining a proper and safe spa environment—not only to maintain a good level of oxidizers but also to correctly monitor pH, water hardness, alkalinity, etc. However, only a few options are available to spa operators looking to offer healthy water while reducing the dependence on chemical consumption: maintaining high levels of chlorine (between 3 and 5 ppm); non-chlorine shocking; ozone; adding fresh water; or installing a UV sanitizing system.

"Prevention" and a "good filter" go a long way toward helping the filtration system be effective. Outside contaminants enter spas when bathers introduce ammonia and organic compounds. Spas and hot tubs are inherently used for leisure and fun, but combined with warm water, proper sanitization is a must.

A good filter is key. It is always possible to enhance the filter, such as by adding granulated activated carbon, will help remove chloramines and ammonia. Filtering is critical in spa sanitation and may require additional attention and manipulation.

The two main benefits to UV over the other options are: UV damages DNA/RNA at a wavelength of 254 nm so water is sanitized; and studies show that repeated passages through both medium- and low-pressure bulbs decrease chloramine levels down to ranges acceptable to health organization guidelines.

Many hot tubs currently offer UV technology as an option for sanitizing spa water. For commercial spa use, medium-pressure bulb technology is used. The volume of water in conjunction with the volume of bathers needs to be considered with the turnover rate of water flow to properly size the UV unit. If you are thinking about pursuing the UV path, there are a couple of things to consider as all UV systems are not created equal. Are they properly designed to deliver the UV dose necessary to eradicate the water-borne microorganisms? Are the units energy-efficient? A reliable UV system is designed to handle a maximum flow rate. Check with your UV manufacturer about their certifications.

It is important to determine the correct sizing of the UV unit for the type of spa and its use. Water flow is a major factor in determining the size of the unit. And how often the water is turned over each hour is important in properly sizing the UV treatment. Also, does the spa use a circulation pump in addition to the pumps for the jets?

The obvious health benefits of UV water treatment using less chemical and providing a safer bathing environment have made the option of UV treatment for spas very attractive. It is good to know that you're providing a facility with better air and water quality, plus you'll be able to say you are lowering your carbon and water footprint on the planet.


Recreational water illness (RWI) is dramatically increasing. Research has also shown that halogen disinfection creates hazardous byproducts (DBPs). These DBPs include chloramines, THM, HAA and other contaminants that can have serious negative health effects. It is also established that certain pathogens are resistant to chlorine and ozone, thus leading to various diseases including respiratory, skin and gastrointestinal

problems. Awareness and concern about exposure to DBPs in pools and spas is increasing. Health officials have acknowledged that the increase of RWI and negative health effects associated with DBPs necessitates a paradigm shift in our thinking about how we treat pool and spa water.

Experts agree that moving beyond the basics will require revising the two pillars approach that includes filtration and halogen, followed by adopting supplemental disinfection for water quality management for pools and spas.

In-line UV disinfection is recognized as an extremely effective and reliable method for deactivating pathogens in the water and reducing the bather's exposure to DBPs.

In some areas, chemically laden pool or spa water cannot be put to waste as it goes directly through the aquifers and could contaminate the ground water. Water that is treated with UV light usually has drastically reduced chemical levels and can safely be drained.

Now is the time to consider a UV system to improve both the water quality and the air quality of spas and hot tubs.

Jeff Boynton is director of Sales and Marketing for Delta Ultraviolet Solutions, based in Gardena, Ga. Delta UV provides complete and advanced "clean light" technology for eradication of microorganisms and chloramine removal for swimming pools and spas. For more information, visit

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