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Unfiltered Truth About Ozone in Hot Tubs

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Ozone is a molecule composed of three oxygen atoms

Ozone is an unstable molecule composed of three oxygen atoms

What is ozone and what can it do in your hot tub?

Since the early 1990's just about every hot tub manufacturer promoted the use of ozonators (a.k.a ozone generators) as a way to reduce the use of chemical sanitizers such as bromine or chlorine for keeping your hot tub water clean.

Bromine and chlorine leave behind chemical byproducts that eventually accumulate in the small volume of water in a portable hot tub. These byproducts can eventually result in irritating chemical odors and caustic water that can irritate your skin and make soaking unpleasant.

Once chemical byproducts build up to a certain level in your hot tub the only way to fix the problem is to drain out the accumulation of byproducts and refill your hot tub with fresh water.

Hot tub ozone generators

An ozonator produces ozone gas which is injected into your hot tub water to sanitize and oxidize just like bromine and chlorine. Since ozone is not a chemical additive it doesn't leave behind chemical byproducts.

Oxygen (O2) is a stable molecule composed of two oxygen atoms. Ozone (O3) is an unstable molecule composed of three oxygen atoms. The extra oxygen atom makes ozone unstable so every O3 molecule is always trying to get rid of the extra oxygen atom so it can return to being stable O2.

An ozone molecule can get rid of the extra oxygen atom by bumping into a nearby molecule and depositing the extra oxygen atom onto the nearby molecule. When the ozone molecule gets rid of the extra oxygen atom it's called reduction because the ozone moledule is reduced from O3 to O2.

When the nearby molecule such as algae, baceria, a virus or other contamination picks up the extra oxygen atom it's called oxidation because the molecule gains and reacts with the oxygen atom.

Bromine and chlorine use the same reduction-oxidation process to keep your hot tub clean and sanitary but leave behind chemical byproducts. Ozone gas is a much stronger oxidizer than bromine or chlorine so it works much faster and it doesn't leave behind any chemical byproducts.

Ozone kills chlorine-resistant microorganisms

Ozone can quickly destroy even chlorine-resistant microorganisms such as cryptosporidium in your hot tub water by attacking and oxidizing the cell wall killing the bacteria or virus almost instantly.

Ozone can also prevent cloudy water by flocculating or clumping together fine particles of organic and inorganic contamination such as sweat, body oil, dead skin cells, lotions and cosmeticss so they can be filtered out of the water.

  • Instantly kills algae, bacteria and viruses including chlorine-resistant micro-organisms such as Cryptosporidium
  • Instantly oxidizes and destroys organic contamination such as sweat, body oil and dead skin
  • Oxidize and destroy inorganic contamination such as metals, suntan lotion, cosmetics and chemical byproducts from bromine and chlorine
  • Reduce the amount of bromine or chlorine required to keep your hot tub clean and sanitary

An ozone generator sounds like the must-have, fill-and-forget magic gadget that will solve all your hot tub headaches doesn't it?

Don't get drowned in the giant pool of misleading marketing and incomplete information promoted by people and websites whose only interest is to profit from the sale and maintenance of magic gadgets.

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Simple Hot Tub Chemistry vs. Ozone Generator Claims

Simple Hot Tub Chemistry solves the same problems without the added expense of ozone generators

Simple Hot Tub Chemistry vs.
Ozone Generator Claims

Simple Hot Tub Chemistry is based on some fundamental facts that you won't hear from most people who profit by selling hot tub chemicals or ozone generators:

  • You can keep your hot tub clean, clear and sanitary with only 4 products
    1. Test strips or a test kit
    2. pH Decreaser (Sodium Bisulfate)
    3. Granular chlorine (Sodium Hypochlorite)
    4. A fresh batch of water (Dihydrogen Oxide)
  • Most hot tub owners use way too much chlorine to begin with
    • Correct chlorine doses for most portable hot tubs are measured in Teaspoons and Tablespoons not "capfuls"
    • Most hot tub owners don't soak in their hot tubs every day so your hot tub doesn't need a daily dose of chlorine or ozone
    • Your covered hot tub is essentially a sealed tank so it doesn't need a daily dose of chlorine or ozone like an uncovered swimming pool
  • You can refill a 400 gallon hot tub with fresh water for about $2.96
    • A 400 gallon batch of fresh, clean water is cheaper than even 1 pint of any product sold to treat a water quality problem
    • An ozone generator costs $50 to $100, requires an annual service call and must be replaced every 1 to 5 years
    • Just because you can fix a problem by pouring more chemicals into the water or installing an expensive magic gadget doesn't mean you should

Hot tub chemistry doesn't have to be complicated or time consuming. Keeping your hot tub clean and sanitary doesn't have to be expensive. Simple Hot Tub Chemistry solves simple problems without hot tub hassle.

Learn more about Simple Hot Tub Chemistry

You can reduce the use of bromine or chlorine in your hot tub by 60% to 90% simply by understanding your hot tub only needs bromine or chlorine when you soak in it

An uncovered swimming pool needs a constant, daily dose of chlorine because an uncovered swimming pool soaks up a daily load of debris such as dust, pollen, insects and leaves all laden with bacteria.

Claim: ozone reduces bromine or chlorine by 60 to 90 percent

Your covered portable hot tub is essentially an insulated, sealed tank so the water only gets dirty when you remove the cover and soak in the water. Your hot tub doesn't need a daily dose of chemistry unless you soak in your tub every day.

If you follow the Simple Hot Tub Chemistry rotine, most hot tub owners can eliminate 60% to 90% of bromine or chlorine simply by using less; No expensive magic gadget required.

Some ozone generator manufacturers and many hot tub sales people will incorrectly claim ozone can completely eliminate any need for chemical sanitizers such as bromine or chlorine.

Claim: ozone eliminates the need for any chemicals

Ozone is a powerful sanitizer and oxidizer because the O3 molecule is so unstable. Unfortunately, this instability also means ozone has a very short lifespan so dissolved ozone in your hot tub water reverts back to simple oxygen in less than 10 minutes.

A small amount of chemical sanitizer such as bromine or chlorine is still required to provide a residual sanitizer that keeps your water sanitary between ozone cycles.

Hot tubs with ozone still need chlorine

This claim is entirely true but only if you apply the very limited logic used by people who profit by selling ozone generators.

Ozone can reduce the money you spend on hot tub chemicals but it won't save you money overall because an ozone generator uses electricity and must operate 4 to 24 hours a day to keep your hot tub clean and sanitary.

Ozone generator must run 4 to 24 hours a day
  • Any money you save on hot tub chemicals you burn in electricity
    • Ozone generators only work when your hot tub is running a filtration cycle which means a pump is running
    • Power consumption varies by make and model but your hot tub pump will use 100 Watts to 600 Watts per hour during a filter cycle
    • Ozone generators must operate for 4 to 24 hours every day to deliver enough ozone to have any noticeable effect on water quality
    • You burn between 2.4 kilowatts and 3.6 kilowatts every day so you can operate an ozone generator and "save money on hot tub chemicals"

An ozone generator also has annual maintenance requirements and, depending on type, make and model, the ozone generator must be replaced or recharged every 1 to 5 years.

  • You spend $50 to $100 for an ozone generator every 1 to 5 years
    • Ozone generators expire and must be replaced
    • Ozone generator lifespan varies by make and model
    • Ozone generators should be replaced or "recahrged" every 1 to 5 years
Ozone generators expire in six months to four years

Most hot tub owners don't know their ozone generators expire so most hot tubs I work on still have the original, factory-installed ozonator which expired long ago and hasn't produced a useful amount of ozone in many years.

  • You spend $100 to $200 on a hot tub service call to install, recharge or replace an ozone generator
    • Unless you do-it-yourself, you'll have to pay a labor fee for a hot tub service call to install, recharge or replace an ozone generator
    • If your hot tub is not "ozone-ready" the tub will have to be drained so an ozone injector can be installed somwehere in the plumbing
  • You pay $100 to $200 on a hot tub service call every year for routine ozone generator inspection and maintenance
    • Ozone check valve should be replaced annually
    • Ozone supply tubing should be replaced annually
    • Ozone injector should be inspected and cleaned annually
Ozone injector must be serviced annually to minimize off-gassing

This is another claim that's entirely true but doesn't really apply to the small body of water in your private portable hot tub.

Cryptosproidium is a chlorine-resistant microbe that can survive normal chlorine levels up to 10 ppm. Killing cryptosporidium requires hyper-chlorination or raising the chlorine level to at least 20 ppm and maintaining that level for at least 28 hours.

Ozone can kill cryptosporidium almost instantly.

Ozone kills cryptosporidium

Here is what the hot tub ozone marketing claims conveniently leave out about cryptosporidium:

  • Cryptosporidium comes from a 'fecal accident' in your hot tub
  • Hyper-chlorination guidelines are published by the CDC and health departments for public swimming pools
  • The large volume of water in a public swimming pool means it's not practical to drain and refill the entire pool after a fecal accident
  • If somebody has s fecal accident in your hot tub...are you really going to sit in that same batch of water again?
  • You can drain and refill a 400 gallon hot tub with a fresh, clean, sanitary batch of water for $2.96

Don't poop in your hot tub

Poop in a public swimming pool is probably unavoidable. Don't let people poop in your private hot tub and you won't have to worry about cryptosporidium. If you do have a "fecal accident" in your hot tub... When in doubt; Drain it out!

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Ozone inhalation hazard

Ozone Can Damage Your Hot Tub
and Your Lungs

"Some spa manufacturers and service technicians say they enjoy 'the sweet smell of ozone in the tub' — they say it is a signal that the system is working. In truth, what they are smelling is ozone escaping the system, a clear sign that the system is not functioning optimally."

"That can damage users’ lungs as well as hot tub covers and other exposed materials. An effective ozonation system won’t smell like ozone at all, because the ozone is dissolved in the spa water, where it can do its work."

Undissolved ozone gas can damage hot tub covers and headrests

Undissolved ozone gas bubbling up out of the water can quickly burn and bleach the bottom of your hot tub cover. Ozone gas trapped between the surface of the water and the bottom of the cover can also blister and bleach out hot tub headrests.

Most residential ozone generators are rated to to treat 1,000, 3,000 or 5,000 gallons. Most portable hot tubs hold 500 gallons or less so it's easy to overdose a hot tub with ozone. Too much ozone can damage hot tub covers and headrests and expose bathers to raw, undissolved ozone gas.

Ozone can damage hot tub covers, headrests and exposes bathers to raw ozone gas

If you see a bleach mark on the bottom of your hot tub cover directly above the ozone jet it means you might also have raw, undissolved ozone gas bubbling out of the water just inches from your nose when you're soaking in the water.

If you can smell undissolved ozone gas when you lift the lid of your hot tub it usually means your ozone generator is oversized for the volume of water or your ozone injector is not rated properly or working properly.

Almost every ozone generator manufacturer includes a warning somewhere in the instructions, or on the product or on their website:

Warning! Do not inhale ozone gas.

The Material Safety Data Sheet (MSDS) for ozone gas indicates health risk of exposure is "High" and "Inhalation produces various degrees of respiratory effects from irritation to pulmonary edema (fluid in lungs) as well as affecting the eyes, blood, and central nervous system."

MSDS Section VI: Health Hazard Data lists the summary of risks as:

"There is no true threshold limit and so no exposure (regardless of how small) is theoretically without effect from ozone’s strong oxidative ability. Ozone passes straight to the smallest bronchioles and alveoli and is not absorbed by mucous membranes along the way. Initial small exposure may reduce cell sensitivity and/or increase mucous thickness producing a resistance to low ozone levels. Short exposure to 1-2 ppm concentrations causes headache as well as irritation to the respiratory tract. but symptoms subside when exposure ends."

If you can smell ozone while you're sitting and soaking in your hot tub you are inhaling raw, undissolved ozone gas bubbling up out of the water just a few inches from your nose.

If you have experienced eye irritation, lung irritation and headache after using your hot tub and blamed might actually be undissolved gas from your ozone generator (the same fill-and-forget magic gadget that promised to eliminate the irritation caused by chemistry.)

Properly installed ozone generators in commercial and residential swimming pools are designed to prevent swimmers from being exposed to any amount of raw, undissolved ozone gas.

The high-output ozone generator is installed in the pump room far away from the water. Ozone gas is injected and then mixed in a special chamber. A special de-gas valve removes any raw, undissolved ozone gas and an ozone destruct device ensures no undissolved gas escapes the system anywhere near swimmers or pool maintenance workers.

Ozone mixing chamber, de-gas valve and destruct device
  • Ozone in commercial pool systems utilize:
    • An isolated ozone mixing chamber to dissolve as much ozone gas into the water as possible
    • An isolated 'de-gassing' chamber to remove undissolved ozone before it is delivered to the pool
    • An isolated "ozone destruct device" to destroy undisolved ozone

Association of Pool & Spa Professionals Ozone Generator Fact Sheet

  • Ozone systems in portable hot tubs utilize:
    • A device that injects raw ozone gas directly into the water stream
    • Most portable hot tubs do not use an isolated ozone mixing chamber
    • If you can smell ozone bubbling up inches from your nose while you're soaking in your tub you are breathing raw, undissolved ozone gas

Very few portable hot tubs have ever used ozone mixing or reactor chambers and even fewer have ever used de-gas valves or ozone destruct units.

Most portable hot tubs equipped with ozonators inject ozone gas directly into the water stream. If you can smell ozone while soaking in your tub you are breathing raw, undissolved ozone gas.

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