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Ultraviolet-UV Spa Sanitizers

Sanitizes without chemicals and reduces chemical usage.
 
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Sanitizers With Fewer Chemicals
 

 
 

Scroll down to browse through some archived SPA and Hot Tub questions and answers.  Please click the Spa Topics Link, on top of every page, to access a complete listing of Spa and Hot Tub Problem subjects, an alphabetized Website Table of Contents, Spa and Hot Tub Equipment Information, About Alan Biographic Material and a Spa and Hot Tub Glossary. Use the other links to access additional subject information. More information about some new and unique products, for Spas and Hot Tubs, can be found by visiting The Website Store. You'll never know what you'll find and that's always fun. Be better prepared and avoid costly problems!

 
Mini Salt Chlorine Generator, for spas and swim spas. SmarterSpa Salt Chlorine Generator for Spas. Model SV battery-powered Spa Vacuum.
One of the ColorQ all-digital, pool and spa water analyzers. Nano-Stick Clarifiers, forall types of pools and spas.
Dual-Cartridge Filter System. Ultraviolet sterilizers/sanitizers can kill some of the most chlorine-resistant pathogens.  However, it cannot be used as a stand alone sanitizer.  It has to be used with an oxidizer, and persistent sanitizer, such as chlorine or bromine. In this manner, it kills microbes, that other sanitizers might not. BlasterAutomatic Filter Cartridge Cleaners for pools and spas.

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How to use ultraviolet (UV), as part of an alternative spa or hot tub sanitizing program? UltraViolet (UV) light can be used as an alternative sanitizing method to very effectively destroy microorganisms in spa or hot tub water. Up to 99.9% of the microorganisms can be destroyed, as the water passes through the UV unit. This dramatic reduction, in the microbial populations, helps to better maintain proper, sanitary spa water conditions: reducing the amount of chemical sanitizer needed to maintain water quality and to keep the underwater surfaces free of bacteria and slimy deposits. Typically, an Ultraviolet Sanitizer is plumbed inline and operates with the filter pump cycle. Water passing through the cell is efficiently sanitized, as the ultraviolet light passes through the microorganism's cell membrane. UV Sanitizers are capable of killing resistant, pathogenic microorganisms, such as Giardia and Cryptosporidium. If problems arise, refer to the Spa Problems Page, as a source of problem-solving information, broken down into various categories.  Scroll down the page and click on the linked keywords, catch phrases or images, in the archived answers below, to access additional information, on that topic or product.

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▼     Helpful, Problem-Solving Information, in a question and answer format.     ▼

Ultraviolet Alone Is Not Enough?

I have a 400 gallon spa with UV and micro filter. I live in an area with very hard water, over 390+, I have been using the hard water to fill the tub. My wife and I use the tub daily. I've been having trouble keeping my spa chemicals balanced, specifically high pH, I am constantly adding pH lower, but the pH always remains on the high side. Also, the water isn't as clear as I would like it, not real cloudy, but a dingy look, and at times we get skin irritations. I use chlorine, 2 table spoons about 3 times per week and shock it weekly. I also use a stain and scale inhibitor weekly.

I have a water softer on our house that maintains the hardness at around 20 PPM. Should I be using the soft water or the hard water to fill the tub, or a mixture of both to help control pH and water clarity.  Thanks.

Ken H., 10/20/2016 SmarterSpa Salt Chlorine Generator for Spas.

Ultraviolet (UV) Sterilizers do not kill bacteria, present in the spa. It kills virtually everything passing through the cell and will reduce the population, but has no effect on anything growing on the walls. That is probably why the water looks dingy and you get irritations. Ultraviolet sterilizers must be used with a persistent sanitizer, such as chlorine. You need to add enough chlorine to maintain 1-3 PPM. You are probably not adding enough or adding it often enough. I don't suppose that anyone bothered to tell you that. UV will allow you to use less chlorine, to maintain any given level, but you need to maintain an appropriate level, at all times. Adding a salt chlorine generator will allow you to maintain a proper chlorine level, with a minimum of effort, and eliminate the need to measure, handle, store or shock, with standard chlorine products. We offer 5 no-installation required models. Two are smart enough to only turn themselves on, when chlorine is actually needed, so you'll never over-chlorinate again.  As concerns the irritation, I suggest consulting a medical doctor.
One of the ColorQ all-digital, pool and spa water analyzers.
Yes, by all means use a combination of tap and softened water. You want a hardness of around 200 PPM. A reading of 390+ could be 800 PPM. To be
sure, mix 1 part of tap water, with 3 parts of store-bought distilled water. Test and multiply the test result by 4, to get a more accurate and truer hardness reading. If it turns out to be 400 PPM, then use an equal mixture of tap and softened water. Otherwise, adjust the proportions. You do have the option of using all softened water and adding the small required amount of calcium hardness booster. I would opt, for the latter.  A ColorQ all-digital tester can do all the required tests and measure calcium hardness, up to 700 PPM, without resorting to dilution.  pH is something that needs to be controlled and is affected, by the chemicals being added.  I hope that this is helpful.

Sincerely.  Alan Schuster, 10/20/2016
 

Chlorine Use With Ultraviolet Sanitizers?

Hi Alan, I Just purchased a new SPA with UV and aware that you don't need as much chlorine when you have UV filtration. I appreciate that you still need some chlorine when you have UV but after researching am aware that you don't need as much. So how do you test for Chlorine, every time I test after the kids have been in the SPA using test strips the chlorine level is low and I need to add a couple of table spoons. To me this seems like there is no benefit to the UV as I am adding as much chlorine as I would if the UV was not fitted. Therefore are there different chlorine levels I should work towards if the UV is in place.  Cheers.

Dim D., 10/23/2014

You are correct that you don't require as much chlorine, but you are missing one important point. You need to sanitize water and oxidize wastes. Ultraviolet Sanitizers do a great job of sanitizing the water, as it returns to the spa. It has no residual action and cannot kill microorganisms in the spa or destroy wastes. It will reduce the overall microbial populations and destroy some seriously pathogenic microorganisms, thatChlorMaker Drape-Over Salt Chlorine Generator, for spas and swim spas. could be resistant to common sanitizers. Chlorine will act to oxidize wastes and provide a residual sanitizer. Because you have an ultraviolet sanitizer, you will require less chlorine to maintain any given level of chlorine. I suggest maintaining 1-3 PPM of free chlorine. The UV provides the benefit of eliminating the odorous and irritating forms of chlorine. How much chlorine will be required to maintain 1-3 PPM will depend on how the spa is used, how many people use it and for how long it is used. UV sanitizing should make it easier to maintain satisfactory conditions, but you should still maintain 1-3 PPM of free chlorine. In addition, the other aspects of spa water chemistry, such as pH, total alkalinity and calcium hardness, should be optimized, on an ongoing basis. For a convenient reliable way to test the water, I suggest a #2056 ColorQ PRO 7 Digital Water Analyzer.  The bottom line is that UV can be the best defense about sanitizing issues, when used properly and in conjunction with chlorine.  Instead of using conventional chlorine, you have the option of using a salt chlorine generator. The combination of salt chlorination and UV sanitizing is a highly effective combination. For more about some affordably-priced, spa model salt chlorine generators visit the salt chlorine generator store.  I hope that this information will prove helpful.

Sincerely.  Alan Schuster, 10/24/2014


Cryptosporidium?

I recently returned to the US from Central America and found out that I had a cryptosporidium infection. I had been in our hot tub since our return. I went online and found out that cryptosporidium is hard to kill and resistant to chlorine. How do I sanitize my hot tub? We have been using biguanide. Would a UV unit be a wise investment, as we do travel often? Thank you.

Joyce B., Albuquerque, NM, 12/2/2013


Ultraviolet (UV) Sanitizers are one of the most effective ways to eliminate potential problems caused by protozoa, such as Cryptosporidium or Giardia. It is certainly one of the worst offenders, all of which are usually killed by UV. Bacteria are generally inactivated, by chlorine disinfectant
, in properly maintained swimming pools and spas, in less than an hour at a minimal concentration. Protozoa, especially Cryptosporidium, are highly resistant and can survive for up to 10 days at typical chlorine concentrations in pools or spas.  You can't use UV alone, because it does not oxidize, will not kill microorganisms on the walls and is not persistent. Most often it isMini Salt Chlorine Generator, for spas and swim spas. used with chlorine. It kills virtually everything in the return flow and chlorine eliminates the wastes and provides persistent continuing sanitation. If reduced chemical usage is the intent, UV sanitizing is the place to start!  UV treatment will reduce the microbial populations in the return flow to near zero, without the use of chemicals. How much chlorine will be required, will depend upon actual bather usage. More usage will require more chemicals. In order to assure that adequate oxidation and sanitation exist at all times, I suggest that you try and maintain a level of chlorine, at about 1/2 the normal level. A salt chlorine generator is ideal, for this application, as it avoids measuring, handling and storage of chlorine products.  The UV unit will help decrease microbial populations and reduce the amount of chlorine, necessary to maintain any given PPM level, by a considerable amount. Over time, charting the amount of chemicals added, the bather usage and the chlorine level will provide the best indication of actual chemical requirements. I consider biguanide a poor choice to sanitize a spa. It adds to the foaming and that makes sanitation more difficult, as the foam harbors microorganisms and the sanitizer level is usually too low. To truly sanitize a spa, all foam has to be periodically eliminated. I hope that this information will be helpful.

Sincerely. Alan Schuster, 12/2/2013


The Fewer The Better?

I realize that you must have some chemicals present, in order to have sanitary conditions. I would rather go with a system or product that allows me to use fewer chemicals. Currently, I am using granular chlorine and would like to switch because I just don't like the omnipresent chlorine odor. Helpful advice will be appreciated.

Bob H., Tampa, FL 2/17/2014

SmarterSpa Salt Chlorine Generator for Spas.
When it comes to spas, I agree that less can be better. Chemicals tend to build up much quicker in a spa than a pool because of the
volumes involved. Less may be better, but it has to be enough to do the job!  There are several options that do not include chlorine. An ozonator, combined with a mineral sanitizer, salt chlorine generator or a bromine, will provide effective sanitation and little or no odor. Alternately, you could use an UltraViolet Sanitizer and a lower level of chlorine, to provide complete sanitation with reduced amounts of chemicals and less odor. Either way, the amount of chemicals required for sanitizing purposes will be reduced. The pH, total alkalinity and calcium hardness will have to be maintained to maintain bather comfort and avoid corrosion. I hope that you'll find the information helpful.

Sincerely. Alan Schuster, 2/17/2014


Oxidizer And Sanitizer Levels?

I AM A POOL AND SPA SERVICE / MAINTENANCE CO. I AM PUTTING AN 800 GALLON SPA IN AND DECIDED TO PURCHASE A UV UNIT. I WAS THINKING OF USING HYDROGEN PEROXIDE WITH THIS, BUT DON'T KNOW WHAT LEVEL TO KEEP THE HYDROGEN. PEROXIDE AT. DO YOU KNOW? IF YOU HAVE ANY IDEAS ON THE UV AND WHAT ELSE I SHOULD USE, PLEASE ADVISE. EXAMPLE: UV AND NON CHLORINE SHOCK 1 TIME PER WEEK, UV AND 0.5 CHLORINE ALL TIMES. LET ME KNOW WHAT YOU THINK. THANK YOU.

ERIK, 12/20/2010


Ultraviolet (UV) sanitizing will reduce the microbial populations in the return flow to near zero, without the use of chemicals. However,
it cannot oxidize wastes or totally eliminate the microbial population in the spa water or prevent the growth of biofilm on the underwater surfaces. You are correct in recognizing that products such as hydrogen peroxide, chlorine or non-chlorine shock must be used. How much will be required will depend upon actual spa usage. More usage will require more chemicals. In order to assure that adequate oxidation and sanitation exist at all times, I suggest that you try and maintain a 0.5-2 PPM level of free chlorine. The UV will help destroy irritating and odorous chloramines. Hydrogen peroxide alone may not adequately sanitize the spa proper. Chlorine will provide the necessary oxidation and sanitizing residual. The UV unit will help decrease microbial populations and reduce the amount of chlorine necessary to maintain any given PPM level. Over time, charting the amount of chemicals added, the bather usage and the chlorine level will provide the best indication of actual chemical requirements. I hope that I have been helpful.

Sincerely. Alan Schuster, 12/20/2010

I was told UV breaks down chlorine and bromine. What should I use with my UV system for my spa? The amount it breaks down is small, compared to the amount that it saves by its effective sanitizing. Thank you.

Erik, 12/23/2010


UV sanitizers have minimal effect on the chlorine and bromine, because of the choice of wavelengths. In addition, it will only have an effect on the water that is passing through the cell. It will still be possible to maintain a chlorine level in the spa. After the unit is shut off, this chlorine residual will be able to provide continuing sanitation. The UV should make it easier to maintain a free chlorine level because the UV will destroy chloramines (irritating and odorous) and will reduce the microbial populations that would, otherwise, consume chlorine.  I suggest that you use chlorine and chart the readings and the bather load. This should enable you be better predict chemical usage. At first signs of a loss of water quality, you could shock the spa with chlorine, non-chlorine shock or hydrogen peroxide. The maintaining of about 1 ppm of free chlorine will help assure proper sanitation and water quality. I hope that this information proves helpful.

Sincerely. Alan Schuster, 12/23/2010
 

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UV And Ozone?

Thanks for your help. I just purchased a new hot tub and it is coming with both a UV Sanitizer attached to the 24 hour low-speed pump and an Ozonator. Both of these units will be running 24 hours a day along with the circulation system. .With two separate units running, do I still need to use Bromine or Chlorine in my tub? I know both the UV and Ozone do different things within the hot tub. We are sensitive to chemicals and are trying to use little to no chemicals, if possible. I purchased a Magnetizer from your website, that will be attached to the tub with the UV light and Ozone system running 24 hours a day. If I need to use Chlorine or Bromine, what is the smallest PPM, I can get away with?

Chris G., 12/7/2008

MegaChlor salt chlorine generator, for spas and swim spas.
You are wise to ask this question. UV Sanitizing is great, but it does nothing to what is grow
ing in the spa. However, it kills nearly everything in the return flow, including some of the worst microorganisms. Ozone Generators will oxidize and destroy wastes, but might not positively assure sanitizing. It is not long lasting, but running it 24/7 will help. Adding some chlorine will provide a persistent sanitizer. I would try to maintain 0.5-1.5 PPM. If the equipment is operating properly, it will take very little chlorine to maintain this level and there should be little or no chlorine odor. A little sodium dichlor is probably all you require. If all it takes is a small amount of chlorine, it is confirmation, that proper conditions are being maintained. A salt chlorine generator can also be used and works really well with ultraviolet sterilizers. Enjoy the hot tub and I hope that I have been helpful.

Sincerely. Alan Schuster, 12/7/2008
 

Where Does the Chlorine Go?

We are new spa owners and use chlorine as the sanitizer.  I don't understand why a spa, with chlorine and pH levels where should be, changes so much when you get out. The chlorine levels, especially, are much lower.  Is this typical of spa operation?  We are new owners, but I didn't realize that you should add chemicals after, or before, each use.  Guess  we have a few more things to learn.

Wanda P, Florida, 9/15/2009


The typical Florida pool has about 60 times more water than your spa.  The spa is at a much higher temperature and this will produce
more bather wastes. This result is that the typical spa places more demands on its sanitizing system, than a typical pool. Sanitizer levels can be depleted very quickly. It just seems like the prudent thing, to test the spa water and add more chlorine before and after each use, as might be required.  If the spa is equipped with an ozonator or Ultraviolet (UV) Sanitizing unit, less chlorine will be used. Ozone and UV units have significant, controllable effects on the sanitation, while chlorine effectiveness rises and falls with its concentration. These alternative methods of sanitizing spas are more flexible and provide a higher degree of effectiveness, wit the addition of a backup system. Much of the chlorine or Ozone is used to destroy organic wastes and byproducts, that cannot be removed by standard spa filters.  I hope that I have addressed your question.

Sincerely. Alan Schuster, 9/15/2009


Baptistery Sanitizing?

My name is Jessica, I work at a Church. We have a 500 gallon spa (we use as a baptistery), and are trying to find out what the best type of sanitizer to use for it would be, the baptistery is mostly used 3-5 times a week for a few minutes at a time. With the type of finishing that we have chlorine is absolutely prohibited. I don't know much of anything about ultraviolet lights or the Ozone. If you could help me figure out what would be the best thing to use that would be great. Thank you for your time.

Jessica R., 2/27/2006


Ultraviolet sanitizing works without chemicals to control microorganisms, but needs to be used with an oxidizer to eliminates wastes and
organics. The combination on a UV Sanitizer and potassium monopersulfate or hydrogen peroxide should work well and impart very little chemical sensation or odor. Adding a mineral sanitizer will add a sanitizer backup. Ozone Generators should be suitable, given there is adequate ventilation, within the church facility. I hope that this information will prove helpful.

Sincerely. Alan Schuster, 2/28/2006


Floatation Chamber Sanitizing?

I have a floatation chamber, using a very high concentration of Epsom Salts (about 280 kgs/500 litres water). Due to the extremely high concentration of salt, water is 99% sterile, and in order to achieve 100% an additional sanitizer/oxidizer is required. Which would your recommend.  Ozonator? UV? Brominator? Keeping in mind the high salt concentration, could be any damage to the system? Because of the salt content, will corrosion be an issue?

Mike T., 9/9/2008


Ultraviolet (UV) Sanitizers will sanitize the water without chemicals and in an enclosed space, that is very important. Bromine will sanitize the water and oxidize the wastes, but odors might present a problem in the enclosed tank. If an Ozonator is used, ozone gas will accumulate in the enclosed air space and might required a venting procedure.  While UV will sanitize the water very effectively, something must be added to oxidize the accumulating waste products. Hydrogen peroxide can be used for this purpose and would not create an odor problem.  So far as corrosion is concerned, you need to make sure that dissimilar metals are not in close proximity, to one another.  I hope that I have been helpful. Enjoy the experience!

Sincerely. Alan Schuster, 9/9/2008


Effect On Bromine?

If the Sun's ultraviolet has a negative effect on bromine, what effect do UV sanitizers have on the bromine level? Is there a difference with chlorine? I would like to reduce the use of bromine used in my spa, by adding a UV sanitizer. Please shed some light on this. Thank you.

Martin H., 7/23/2005


Sunlight is UltraViolet-A (UV-A) and this wavelength does destroy chlorine and bromine. All residential UltraViolet Sterilizers use the
UltraViolet-C (UV-C) wavelength, which is different than Sunlight. To help minimize the effect of the UV on bromine or chlorine, it is necessary to install all chemical feeders downstream of the UV sanitizing unit. A small amount of chlorine or bromine will be destroyed by UV-C. In the process those irritating and odorous chloramines will be destroyed. However, the reduction in the bromine or chlorine usage is still far greater than the 2-5% lost due to the UV-C. Install the chemical feeder last in line. I hope this information is helpful.

Sincerely. Alan Schuster, 7/23/2005


How Is A UV Sanitizer Used?

We moved into our new home and found out the spa has a UV Sanitizer. When I tell people around here about it, no one knows anything about them. Having one of these should mean I can use lower chlorine levels, but how do I know when the water is safe, the tests strips show you how much to keep your levels at for a normal spa, not for one with this UV device.

Eric B., 7/26/2006


Your UV (ultraviolet) Sanitizer does not register on any test strip. What it does is sanitize the water, as it returns to the spa. It cannot sanitize the spa surfaces or oxidize wastes and contamination. To do this you should use chlorine. With a UV sanitizer in place, you will require less chlorine to maintain proper conditions and consume less chlorine in the process. In addition, the UV will destroy the irritating and odorous chloramines. Just test the water for free chlorine, as would be the case if only chlorine was being used. In addition, the pH, total alkalinity and calcium hardness need to be maintained. I hope that I have helped explain the use of the UV device.

Sincerely. Alan Schuster, 7/26/2006

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