A hot tub ozonator is a small generator that makes ozone gas and feeds it into your spa water while the filtration cycle runs. The ozone breaks down oils and contaminants, then turns back into oxygen. It helps your sanitizer, but it does not replace it, and the part wears out. Sources we checked put the typical life at about 3 to 5 years, so plan on replacing it at some point.
For the bigger picture on choosing a tub, see our hot tub buying guide.
What a hot tub ozonator does
Ozone (O3) is a form of oxygen with an extra atom. ClearWater Tech, an ozone equipment maker, describes it as an unstable gas with a very short half life: it reacts with organic matter, oxidizes it, and then reverts to oxygen.
Canadian Spa Company says the ozonator injects ozone to help disinfect the water and break down organic material such as body oils, dead skin cells and hair. Because ozone disappears quickly, it leaves no lasting protection. Our salt water vs chlorine hot tub guide explains why you still need chlorine or bromine alongside it.
Is an ozonator required?
No. It is an add-on, not a requirement. Balboa Water Group, which makes spa controls and ozone units, says its ozonator reduces the need for chlorine and bromine.
Corona discharge vs UV ozonator
ClearWater Tech describes the two ways to make spa ozone:
| Point | Corona discharge (CD) | UV lamp |
|---|---|---|
| How ozone is made | Air passes through a high voltage field | Air passes a UV lamp |
| Output, per ClearWater Tech | Can generate much higher levels | About 0.5% concentration or lower |
| Complexity and cost, per ClearWater Tech | More sophisticated | Less expensive |
| Sign it is on, per Leslie’s | Small vibration sound on CD chip units | Blue glow from the bulb |
One caution on UV units: LoveYourHotTub, a DEL Ozone parts seller, notes that a UV bulb can keep glowing long after its ozone output has dropped, so a lit bulb does not prove the unit is working.
Balboa lists its Ultrazo3ne as a CD unit that runs on 120V, 240V or dual voltage and has epoxy potted cells to keep water out.
Where the ozone enters the water
The ozonator sits in the equipment bay, usually near the control box. A thin tube carries the gas from the unit to the plumbing. ClearWater Tech says the gas is drawn into the water by negative pressure, or vacuum. That suction comes from an injector fitted in the water line. LoveYourHotTub recommends a Mazzei injector and notes that a clogged injector can stop ozone from reaching the water.
Between the tube and the injector is a one way check valve. Canadian Spa Company says the check valve lets only air pass from the ozonator toward the spa. When it fails, water can run back up the clear tube toward the ozone unit. If you replace one, its printed arrow should point toward the tub, away from the generator. See its check valve guide.
Run times follow your filtration cycles
On most tubs, you do not set ozone run time separately. Canadian Spa Company says its ozone generator only turns on while the spa runs a filtration cycle, shown on the topside as FLTR1, FLTR2 and so on. So the amount of ozone your water gets depends on how long your filter cycles run. Short cycles mean less ozone. If the pump will not circulate after a refill, no ozone moves either; our hot tub airlock guide covers that.
Is my ozonator working? Signs to check
- Indicator light. Open the cabinet during a filter cycle. Canadian Spa Company says that if no light is on during the cycle, the ozonator is not working properly. Leslie’s adds that on some units the light only shows power, not ozone output.
- Fine bubbles at the ozone jet. Leslie’s Pool Supplies describes ozone as tiny “champagne bubbles,” under 1 mm. Larger bubbles are usually plain air, and some systems mix in air all the time, so bubbles alone are not proof.
- Smell. Leslie’s says most people can smell ozone at low levels, and it is strongest when you lift the cover after hours closed.
- Water quality. If the water has been cloudier or needed more work, and you have ruled out filters, balance and sanitizer, low ozone output may be the cause. Our cloudy hot tub water guide covers those other causes first.
Water in the clear tube or a leak at the unit points to the check valve. Canadian Spa Company also notes that chemical damage can corrode the generator and cause leaks.
How long does a hot tub ozonator last?
Expect it to wear out. Leslie’s says newer DEL ozonators last 3 to 5 years, while older models need a new bulb or renewal kit every 18 to 24 months. LoveYourHotTub puts the average at about 3 years, with a range of 18 months to 7 years depending on type and how many hours it runs.
Leslie’s also says ozone makers recommend replacing the ozone hose, check valve and injector every year, because a failure in one of those often looks like a dead ozonator. On Canadian Spa Company tubs built after 2016, a “CHEK O3” reminder appears once a year to prompt that check.
Replacing a unit usually means opening the control box. Canadian Spa Company’s replacement steps start with turning off power at the GFCI. If you are not comfortable working near wiring, hire a qualified spa technician or licensed electrician, and follow your manual and local code.
Ozone safety, indoor tubs and soaking
Ozone in the water is not the concern. Ozone gas in the air is. The U.S. EPA says inhaled ozone can damage the lungs, and relatively low amounts can cause chest pain, coughing, shortness of breath and throat irritation, and may worsen asthma. ClearWater Tech notes that a properly designed and installed system should not expose people to irritating levels.
Simple habits help. Lift the cover and let the space air out for a moment before you get in. If your tub is indoors, ventilate the room and follow the maker’s ventilation guidance in your manual. If you have asthma or another lung condition, or any heart or health concern, talk with your doctor before soaking. Hot tubs are for relaxing; any health benefits are manufacturer claims, not medical advice.
Hot tubs we carry with a hot tub ozonator
Several American Spas models list a “Hydro clear ozonator” that, per the listing, uses a corona discharge cell:
- American Spas 7-Person 45-Jet Bench Spa, $7,800: 6.0 and 4.0 BHP pumps, 5.5 kW heater.
- American Spas 6-Person 45-Jet Lounger Spa, $7,700: lounger version of the same setup.
- American Spas 7-Person 40-Jet Bench Spa, $7,300: one 6.0 BHP pump.
- American Spas Dual Voltage 6-Person 18-Jet Plug and Play, $7,100: plugs into a 110V/15A outlet or can be hardwired.
These Canadian Spa Company models list an ozone generator (the Richmond and Alberta also list Glacier antimicrobial filtration):
- Granby 4-Person 15-Jet, $7,750: plug and play, 50 sq ft of filtration plus a built-in ozone generator.
- Richmond 6-Person 27-Jet Plug and Play, $10,249: 120V/15A, 900 L capacity.
- Alberta 6-Person 55-Jet, $18,749: 240V/60A, ozone plus 100 sq ft of filtration.
Prices are as listed at the time of writing.
Frequently asked questions
Does a hot tub need an ozonator?
No. It is optional. It can cut the amount of sanitizer you use, but you still need chlorine or bromine in the water.
How long does a hot tub ozonator last?
Leslie’s puts newer DEL units at 3 to 5 years. Check the hose, check valve and injector each year.
Is a corona discharge or UV ozonator better?
ClearWater Tech says corona discharge can make much higher ozone levels, while UV units cost less. Use the type your spa maker specifies for your model.
Is my ozonator working if I see bubbles?
Not necessarily. Some systems mix in air, so also check the indicator light during a filter cycle.
Questions about your tub?
Call us at 866-777-2590, Mon-Fri 9AM-6PM PST, and we will help you compare models. Orders of $999 or more ship free freight, and orders below that ship for a $200 flat rate. Before you buy, read our return and refund policy.
