Hot Tub Ozonater?


May 17, 2007
Shepherdsville, KY
Hello all! We were recently given a brand new hot tub shell so I have been shopping around for all of the equipment I am going to need. This one web site says to use an ozonater for your sanitizer. Does anyone know what this is exactly? Is this like all of the other "amazing mineral" junk the pool stores try to sell?


In The Industry
Mar 29, 2007
Knippa, Texas
You don't NEED an ozonator; there are pros and cons. There are others here who know more about them, but my impression is that it's not really worth it.

Bromine is often recommended (instead of chlorine) as a sanitizer for hot tubs. Don't know if you're familiar with chlorine chemistry, but if you are, be advised that bromine works quite differently! There's a "primer" for using bromine posted in this "Spa/Hot tub care" section; refer to that.

The "mineral" sanitizers usually contain metals, copper, maybe silver, maybe zinc. These DO kill the nasty microbes, BUT the problem with them is they don't kill them fast enough. And metals in your water can cause staining.

The nice thing about a hot tub is that you can try different sanitizers sequentially, since you have to drain and refill every few months. Bromine is more stable in high temperature water, and combined bromines are not "used up" like combined chlorines (cc's). Bromine also sanitizes in a wider pH range than does chlorine. But bromine can't be stabilized against sunlight (not a problem if you keep the tub covered when it's not in use). Bromine is also more expensive than chlorine.

One product that's really not necessary in a pool (except maybe an indoor pool:) but almost ESSENTIAL in a spa is an enzyme treatment. With the smaller volume of water, a spa will have a higher level of organic contaminants. To prevent the "tub ring," use an enzyme treatment such as Spa Perfect or Scum Buster. The enzymes help "digest" organics so that your sanitizer doesn't have to work as hard.

Other folks can chime in about ozonators; I don't know a great deal about them, but you can keep your hot tub sanitized just fine without one.

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
San Rafael, CA USA
The biggest plus with a functioning ozonator (not all work properly or put out enough ozone to work well) is that it will oxidize many contaminants in the water, but it's not fast as it takes time to get water circulated through the ozonator. Though spas circulate water faster than pools, it still takes 4.6 turnovers of the water to get 99% of the water through the ozonator and that's assuming no dead spots. You still need a residual sanitizer if you're going to prevent bacterial growth in the bulk pool water.

The biggest minus with an ozonator is that it mostly injects air into the water and that aerates the water. If the ozonator is always on (and many are), this leads to a rise in pH if you use a hypochlorite source of chlorine. So many spa users use Dichlor which is acidic (when accounting for chlorine usage) and this helps maintain the pH, but has the CYA rise.

An ozonator probably makes more sense in a bromine spa than a chlorine spa as it can reactivate the bromide to bromine (though can create bromates -- so don't drink the water) and most bromine systems are net acidic so the pH will be more stable with the ozonator. As was pointed out, it is technically unnecessary if one maintains a residual sanitizer (chlorine, bromine, PHMB/biguanide/Baqua).

Just keep in mind that the sanitizer usage in a spa is MUCH higher than in a pool due to the lower water volume (higher bather load) and higher temperature that causes one to produce more sweat and causes chlorine to outgas more (especially with an ozonator).



LifeTime Supporter
Mar 31, 2008
Central VA
I have an ozonator, but along with it I use an ion cartridge that just slips into the main (24-hour circulation) filter in my spa. We had Baquacil in the spa until we got overrun with white mold and couldn't get rid of it (even after repeated drain/refills :x ), so we tried to ozone/ion combo. and it seems to be working great -- clear water, and we use VERY little chlorine with it...and very little maintenance.
BUT, I'm going to start a new post as soon as I test the water, cause it does get some yellowing and I may need some of Chemgeek's expertise in choosing the correct sanitizer if the Chlorine numbers are screwy.


tnthudson said:
but along with it I use an ion cartridge that just slips into the main (24-hour circulation) filter in my spa.
Be aware that the 'ion cartridge' is just putting metals into your water, usually silver and zinc for a spa, and a residual sanitizer is STILL necessary (read that as chlorine or bromine).


LifeTime Supporter
Mar 31, 2008
Central VA
Thanks, waterbear...I was going to ask this after I got my pool straight, but is bromine better for a spa when using ion/ozone? I read some other posts and got the feeling that it was.
Also, is bromine less likely to cause skin irritation?
thanks again


You need to check your mineral cartridge as to which sanitizer you can use with it. Nature 2 (which is also most common in OEM mineral systems) can ONLY be used with chlorine while SpaFrog can only be used with bromine. I am not a fan of ion or mineral systems. If you have an electric ionizer then they are usually used with chlorine.

As far as ozone, IMHO, it works better with bromine than chlorine since it activates bromine but destroys chlorine.

As far as skin irritation, IF you are talking about an allergic reaction then bromine is more of a sensitizer than chlorine. Also, non chlorine shock (MPS) that is usually used in spas also has been implicated in skin irritation.

The only way to tell for sure is to try bromine and see (you might have to remove the mineral cartridge first if it's not compatible). if there is a problem then just drain the spa and switch back to chlorine.