ultraviolet (UV) pool water sanitizers: chemical-free, ultraviolet (UV) pool water sanitizers

Ultraviolet (UV) light can be used as an alternative sanitizing method to very effectively destroy microorganisms in swimming pool water. Up to 99.9% of the microorganisms can be destroyed, as the pool water passes through the UV unit. This dramatic reduction, in the microbial populations, helps to better maintain proper sanitary pool water conditions: reducing the amount of chemical sanitizer needed to maintain proper, sanitary water quality and keep the underwater surfaces free of bacterial or algal growth. A UV Sanitizer must be used in conjunction with another sanitizing product: chlorine, ionizers or mineral purifiers. In addition, oxidation of waste products must be accomplished with the use of chlorine, ozone, shock or hydrogen peroxide. Most commonly a UV Sanitizer is used with chlorine or bromine and can reduce their usage by a considerable amount. Typically, an Ultraviolet Sanitizer is plumbed inline and operates with the filter pump cycle. Water passing through the cell is efficiently sanitized, as the UV light passes through the microorganism's cell membrane. Clicking on the underlined and highlighted "keywords" or "catch phrases," in the archived answers will give you access to additional information on that topic or product. Please refer to the Glossary, if there are terms or phrases that require explanation. For an alphabetized listing of the entire contents of the website, use the Table of Contents link, on top of every page.

I recently returned home, from a Central American vacation and found out that I had a cryptosporidium infection, as a result of swimming pool use. I found out that cryptosporidium, unlike bacteria and algae, is hard to kill and is resistant to chlorine. How do I sanitize my pool? Would a UV unit be a good choice, as we do travel often? Reducing chemical usage would be a pleasant bonus. Thank you.

Ultraviolet (UV) sanitizers are one of the most effective ways to eliminate of 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 and algae 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. 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 is 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! How much will be required will depend upon actual bather demand. More bather 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. 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. For more information on UV sanitizers go to: www.deltauv.com I hope that this information will be helpful.

Sincerely. Alan Schuster, 12/2/2009

I am interested in getting away from all the chlorine and the odors associated with the product. I know there are several types of alternative pool water sanitizers available, which can reduce or eliminate chemical usage. I've read up on some of them, but am not really clear about Ultraviolet. Is this the same as Ozone? How does it work? Thanks for the help.

Ultraviolet (UV) is not ozone. Some ozone generators utilize UV to produce ozone, but not as a sanitizing agent. UV rays destroy the microorganisms ability to survive and function, after passing through the cell membrane. An ultraviolet sanitizer unit is plumbed inline and effectively sanitizes the water, as it passes through the cell. This has the net effect of reducing the overall microbial populations and reducing the amount of sanitizer necessary to maintain optimum water quality and to keep the pool algae-free. UV will reduce the microbial population, but requires a traditional sanitizer to help keep it that way and to help the underwater surfaces free of algae. Chlorine is well suited, in this role, and lower quantities of chemicals will be required because of the lower microbial populations. Visit www.deltauv.com or www.elektra.com for more complete information on ultraviolet sanitizers. Good water circulation is important and a robotic pool cleaner would be a worthwhile addition, helping to keep the underwater surfaces in algae-free condition. I hope that I have been helpful.

I have a salt water aquarium and use a UV light to control bacteria. I have heard of UV units for pools. Does it work the same way?

Yes and No! In both cases the ultraviolet (UV) light is used to destroy bacteria and keep the populations down. In an aquarium, there must be a viable bacterial (beneficial types - not pathogens) population, in order to decompose and recycle the wastes from the fish and plants. In a swimming pool, the best bacteria are dead ones. The UV light is used to keep the bacterial populations as low as possible, so that the task of pool water sanitizing is easier. Chlorine or other sanitizers should be maintained, at the appropriate levels, in order to provide ongoing sanitation. However, the presence of an ultraviolet sanitizer will allow for a reduction of about 70-85%, according to the manufacturer, in the amount of chlorine or bromine required. The UV unit will make sanitizing easier and involve fewer chemicals and there's nothing fishy about that. I hope that I have been helpful.

My wife and I want to use something to sanitize the pool that will reduce the chemicals needed. We are considering ozone or UV, as neither adds chemicals to the water. What are the advantages or disadvantages? Waiting to hear!

It is true that both systems do not, by themselves, add chemicals to the pool water. However, both of these sanitizing methods require that the overall pool water chemistry - pH, total alkalinity, calcium hardness, etc. - be maintained for bather comfort and to reduce possible corrosive effects. Ozone will require that a sanitizer such as, chlorine, mineral sanitizers or ionization, be used as a sanitizer backup. The ozone will reduce the amount of chemicals used in this backup role. Ultraviolet, for most consistent results, requires a backup sanitizer. Chlorine seems to make the most sense, inasmuch as it, also, acts to fill the needed oxidizer role. The UV sanitizer will greatly reduce the amount of chlorine needed to act in this backup role and will destroy irritating and odorous chloramines. Both ozone and UV have the advantage of reducing sanitizing chemical requirements. With proper pool water management, there should be no disadvantages, as compared to a traditional pool water sanitizer. I hope that I have helped in the decision making. Good luck.

If the Sun's UV rays destroys chlorine and bromine, what happens with a UV sanitizing unit? Where should my chlorine feeder be placed? Thanks for the opportunity to ask a question.

Sunlight is UV-A and this wavelength does destroy chlorine and bromine. All residential UV sanitizers use UV-C wavelength, (254 nm) which is different than Sunlight. Thus, the need to install all chemical feeding downstream of the UV sanitizing unit. A small amount of chlorine or bromine will be destroyed by UV-C. However, it is far less than UV-A loss and the net result of the reduction of chlorine usage is still far greater than the 2-5% chlorine loss to UV-C. Install the chlorine feeder last in line. I hope this information is helpful.

It certainly seems that way. All of the water passing through the cell has its microorganism population reduced to nearly zero. All you need is some free chlorine to help keep it that way and to destroy accumulations of organic wastes. With the UV Sanitizer killing and controlling algae and bacteria, about considerably less chlorine is required, under proper circumstances. In a chlorine pool, odorous and irritating combined chlorine (chloramines) forms and this requires adding shock treatment. With a UV sanitizer, the chloramines are destroyed, without additions of chlorine. The end result is a chlorine pool that looks and smells better. I hope that this information is helpful.

I took a look at the Electra UV systems, the schematic depicts the UV lamp on the output side of the filter, Does it matter? Seems like the input side would be more effective. Kill it prior to the filter, so it doesn't grow inside the sand. Any thoughts? Thanks.

Jim H. 8/17/2008

Filters are loaded with living algae and bacteria. The UV Sanitizer unit has to be installed, after the filter, in order to treat the water returning to the pool. For more information go to: www.deltauv.com Having a low chlorine level, present in the pool, helps to provide persistent sanitation. There is no simple way to keep the filter sterile. I hope that this information is clarifying.

Is there any systems in which you can use an ozonator and UV? So no need for Chlorine or Bromine. Also what are your feelings on Steel vs. Concrete pools under the vinyl? Thanks.

The easy one first. I would choose concrete: it stronger, doesn't rust and the walls will not bow or flex. You can add UV Sanitizing and an Ozone Generator, but as two separate units. It will virtually assure you that the return flow will be devoid of living algae and bacteria. However, the pool walls and water can still support algae and bacteria. Keeping a low level of chlorine, about 1 PPM, will prevent growth in the pool and on the walls. The ozonator will carry the burden of oxidizing wastes and very little chlorine will actually be required. The odorous form of chlorine will be destroyed, as the water returns to the pool. There should be little or no sensation of chlorine. The fact that you will be able to maintain this low level of free chlorine, with only minimal amounts of chemicals, will act as conformation that proper conditions exist and that everything is functioning properly. For more about UV sanitizing go to: www.deltauv.com For more about ozone generators go to: www.waterquality.net If you add the relatively inexpensive Circulators, to your returns, that will eliminate any dead zones that could promote algal and bacterial growth. I hope that you will find this information helpful.

I have been using biguanide for several years and been happy with the results. It may cost more, but I like the feel and the lack of chlorine odors. The problem is that on two occasions the pool has developed a water mold. I had to add chemicals and chlorine shock and, in effect, had to start all over. The dealer says it could happen again. Short of switching to something else, can you suggest an alternative? Thanks.

You could try adding an UltraViolet Sanitizing unit. It will depress the microbial populations and help prevent a possible recurrence. If the problem does recur, you really should permanently switch from biguanide. In that case, you could change to chlorine or bromine and the UV unit will allow you to maintain satisfactory sanitizer levels with far fewer chemicals. It's your call. Good luck with your decision.

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