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Hot tub / spa chemicals & water test strips (C) Daniel FriedmanOzone Use in Hot Tubs, Spas, Swimming Pools
Guide to hot tub, spa, pool water ozone treatment

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Hot tub & spa or whirlpool bath chemical & water treatment using ozone generators:

Here we provide a simple table showing how to use chlorine or bromine and other chemicals & treatments to maintain a hot tub or spa, We explain how to use simple test strips to test the level of chlorine, bromine, pH, alkalinity, hardness and other spa or hot tub water properties in order to maintain a safe, sanitary hot tub or spa.

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Use of Ozone as an Oxidizer in Hot Tubs, Spas & Swimming Pools

AquaSunOzone Ozone Generator for spas discussed & cited at Inspectapedia.comFreije explains that because their design, use, and water maintenance are different, spas and hot tubs do not function the same nor necessariily present the same hazards as found at public swimming pools.

Illustration: the Pacifica Spa Series XL-30 Ozone Generator from AquaSunOzone, cited in detail below in this article.

[Click to enlarge any image]

Spas and hot tubs are not the same as whirlpool baths. Spas and hot tubs are used for recreation rather than for bathing. Many private spas are located outdoors. They are not drained after each use.

Most have heaters. The water is treated and filtered.... Spas, hot tubs, and whirlpool bathtubs can provide a fertile breeding ground for many microbes, including organisms that cause disease... - Freije (2000)

The use of ozone (O3) has been promoted by some spa, hot tub and swimming pool equipment & supply producers or vendors as an oxidant or oxidizing agent useful to improve water quality by removing " non-living bather waste such as body oils, cosmetics, sun tan lotions, perspiration, urine" and indeed earlier research (Bataller 2000) suggested that ozone might be a useful component of swimming pool water treatment, and as recently as 2013 (Fernández-Luna) authors have suggested that ozone treatments may reduce swimmer exposure to products of other disinfectants used in swimming pool water.

In the pool and spa water, chlorine acts as a primary disinfectant and it provides the safety residual. Ozone is the primary oxidizer. ... When Ozone is used as an oxidizer in pool and spa water, the quality of the water will improve as problems with combined chlorine compounds are eliminated and eye and skin irritations are greatly reduced.

Overall water maintenance and care are minimized as filter runs are longer since clogging greases and oils are broken down, scumline or bathtub rings are kept away or are easily brushed off. The cost of running the pool and spa is lowered as the use of the following specialty chemicals can be reduced: “shock” treatments, scumline cleaners, filter degreasers, clarifiers, scale inhibitors, scents, filter aids.   (Kon, Ultra Pure, un-dated)

Is Ozone all I need to sanitize and keep my spa water clean? The quick answer is “no” but you can eliminate much of your customary sanitizer and shock with a properly functioning ozonator. ... Most hot tubs built in the last 10 years have a built-in ozone generator or are set up so you can add one easily.

So, what is ozone and why is it the best thing for sanitizing your hot tub?... Spa ozone is the most powerful oxidizer and disinfectant that can be safely used in spas. It kills all known bacteria, viruses, yeasts and a lot of other things you don’t want to know about... Your spa ozonator needs to be replaced every 18-24 months. (Cunningham, Olympic Hot Tub Blog, 2012)

Really?

Perhaps not. The ozone-promotion text above, excerpted from some hot tub and spa suppliers selling ozone generation equipment includes errors and is confusing because sometimes this marketing text even contradicts itself, suggesting that ozone is a sufficient disinfectant methods for hot tubs, spas, pools (it is not), at the same time as indicating that ozone is not "all I need to keep my spa water clean".

Indeed ozone has been used in Europe as a component in water treatment in some public swimming pools. But where used in public pools in Europe the effective use of ozone treatment system for swimming water required extensive additional equipment, steps, and monitoring, such as compressors, dryers, contact chambers and deozonators for treating vent gases and for treating ozone–containing water before returning it to the pool (Wojtowicz 2001 citing Eichelsdorfer 1982, Kurzman 1982).

Watch out: Elliot (1989) demonstrated that typically ozone treatment produced by UV radiation was not an effective spa or hot tub or pool disinfection method.

It is concluded that insufficient dissolved ozone is present for a sufficient reaction time to effect disinfection of these organisms by ozone generated by UV radiation. - Elliot (1989)

Wojtowicz (2001) who has written at length about hot tub, spa and swimming pool water disinfection and treatment has found that in general ozone is ineffective for this application and that in any event it should not be used by methods that might expose the hot tub, spa, or pool users to elevated levels of ozone. That author also found that other claims of the benefits of ozone use in hot tubs and spas were not substantiated.

Ozonating the water while the spa is in use is not recommended because the unabsorbed ozone in the ozonator vent gas can amount to 60 ppm. - (Wojtowicz 2001 p. 147)

A number of UV ozonators have been evaluated and found to be unsuitable for pool or spa use. Although UV ozonator manufacturers typically claim lower chlorine consumption (typically 60 to 90%) and the ability to operate pools and spas at lower chlorine concentrations, no independent data are provided to support these claims.  (Wojtowicz 2001)

Papadopoulou notes that even where potentially effective ozone treatment equipment is installed, its maintenance has been poor and various authors reported that some important pathogens are resistant to the ozone treatment. Rigas, adding poor process design as well, noted the same maintenance problems a bit earlier (Rigas 1998).

The swimming pool with the poorest microbiological quality (THC 500 cfu/ml in 12.1% of the samples, P. aeruginosa counts 1500 cfu/100 ml in 6% of the samples) and the highest prevalence of multi-resistant isolates (73.6%) was the hydrotherapy pool - Papadopoulou(2008)

Resistance to chlorine dioxide and ozone for M. avium was 100- and 50-fold greater ... (Lumb 2004)

Zwiener (2007) offers further details about potential hazards of some swmming pool, hot tub, or spa disinfection methods. But those authors do not suggest ozone as an alternative.

... disinfection byproducts (DBPs), such as trihalomethanes (THMs), which are regulated carcinogenic DBPs in drinking water that have been detected in the blood and breath of swimmers and of nonswimmers at indoor pools.

Separately at OZONE HAZARDS readers will find a series of articles about both successful and un-successful, even dangerous applications of ozone. Also see OZONE GAS EXPOSURE EFFECTS.

Research / References: Ozone use in Spas, Hot Tubs, Pools

A2Z Aquatic 3 Spa Ozone Generator from a2Zozone.com discussed & cited at InspectApedia.com

AquaSun XL80 ozone generator for spas cited at InspectApedia.com

Hookup of a typical ozone generator for a spa - adapted from AquaSun Pacifica CSN Xl-80 Ozone Generator at heaterandspaparts.com.au cited at InspectApedia.com

 




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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2019-08-18 by (mod) - what is the right ozone level or ozone concentration for my spa?

Anon: a typical ozone generator for a private whirlpool bath or spa generates 300 mg/hour of ozone gas.

How much ozone is OK? Subjectively, up to the point of smelling ozone; if you smell ozone then the ozone level is too high and may be unsafe. All of the ozone generator providers can be expected to include a warning in their instructions that breathing ozone gas is harmful.

Watch out: You want to follow the instructions for your specific ozone sanitizer for your spa - by brand and model.

An EXAMPLE Spa ozone sanitizer instructions can be read in the CMP manual I'll cite below. However you'll see that other than installing the equipment properly, the company's manual does not give a quantitative measurement of the "right" ozone level for your spa. I suspect this is in part because of the difficulty of defining a precise and accurate measurement procedure that can handle all of the enormously variable installation situations.

CMP DEL OZONE 25/50/100 INSTALLATION INSTRUCTIONS & PRODUCT MANUAL [PDF] CMP, LLC 36 HERRING ROAD, NEWNAN, GA 30265 USA Tel: 800.733.9060 ret. 2019/08/10 original source: https://www.c-m-p.com/wp-content/uploads/2018/05/DEL-Ozone-25_50_100-Manual-1.pdf Web: https://www.c-m-p.com

On 2019-08-18 by Anonymous - what is the ideal levels of ozone in spa water?

what is the ideal levels of ozone in spa water
Thanks
dave
dave98412@btinternet.con

On 2019-07-15 by (mod) - how ozone can be used in spas or whirlpool baths or hot tubs, and its limitations, and safety.

AZ

Thanks for an important question on how ozone can be used in spas or whirlpool baths or hot tubs, and its limitations, and safety.

A spa can generate and use ozone safely while the spa is in use PROVIDED it is working properly and is designed to keep the ozone where it belongs - in the plumbing system, not on the spa occupants.

I'd agree that ozone exposure can be a health concern; ozone is a powerful oxidant that can at high concentrations damage the lungs.

A broad "rule of thumb" is that if you smell ozone the level is high enough that you ought to avoid it; if not, probably not;

In general an ozone generator on a spa is used to reduce the amount of disinfectant needed (it cannot eliminate the need for disinfectant); but ozone should not be entering the space occupied by the spa users.


For example here is an excerpt from experts:

A properly designed ozone or UV system will reduce the amount of chlorine or bromine required.3,5 Ozone is especially effective as a supplement because it destroys matter that "uses up" the chemicals.

Ozone is effective only if the system is sized and designed properly.
The ozone generator must make enough ozone. Also, ozone systems must treat the spa water in an isolated contact chamber
rather than injecting ozone into the spa itself. -

FREIJE, Matthew R. Spas, Hot Tubs, and Whirlpool Bathtubs: A Guide for Disease Prevention. USA: HC Information Resources Inc, 2000, p. 1-3. http://www.whtlimited.com/doc/lib/102/spa-whirlpools-guidance.pdf


Also:

The half–life of ozone in tap water at 20°C is less than 30 minutes. In addition to this thermal decomposition, aqueous ozone is also decomposed by sunlight. Because ozone is a gas, it tends to escape from aqueous solution. This tendency and the fact that ozone is toxic (the maximum allowable concentration in air is only 0.1 ppm for an 8–hour exposure), is the reason that ozone cannot be used as a primary sanitizer. - FREIJE, Matthew R. Spas, Hot Tubs, and Whirlpool Bathtubs: A Guide for Disease Prevention. USA: HC Information Resources Inc, 2000, p. 1-3.
http://www.whtlimited.com/doc/lib/102/spa-whirlpools-guidance.pdf

On 2019-07-10 by Arizona User1 - Should the spa controller allow ozone generation while persons use the spa ?

Should the spa controller allow ozone generation while persons use the spa ? For example, in a two pump spa system, the ozone generator is ON when the Pump 1 low speed is in operation. When Pump 1 is switched to FULL SPEED, the ozone generator is OFF

. However, when the Pump 1 is in low speed and the Pump 2 is ON, the ozone generator continues to be ON. Spa users would be exposed to ozone generated and circulated by Pump 1 low speed operation. Is this a health concern ?


...

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OZONE in HOT TUBS, SPAS, POOLS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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