Sep 03
whats better ozone uv or salt in hot tub

Hot Tub Sanitation what’s better; Ozone, UV or Salt?

Are All Hot Tub Sanitizers the Same?

Built-in hot tub sanitation systems can seem like smoke and mirrors or snake oil to new hot tub buyers, but they really do serve a purpose and each system has its own pros and cons. When trying to absorb all the information about these systems from a salesman it can get a little overwhelming, so we will try and break down each system into its simplest explanation below……as simple as we can anyway 😉

This is a long article you may think about adding it to your favorites or bookmark it so you can come back to it later.

What do hot tub sanitation systems accomplish?

Before we dive into each individual system, there is one thing we need to make clear. There is no sanitation system currently on the market that can completely replace or eliminate the need for a halogen sanitizer like chlorine or bromine. It doesn’t matter what spa you buy or what type of system it comes with you still need to maintain at least a small chlorine or bromine residual in the water for it to be completely sanitized.

The goal of ozone and UV is to lower your overall chlorine and bromine demand so you do not need AS MUCH chlorine or bromine to maintain that small residual, but you still need a small residual in the water. we hear too many horror stories from customers who bought spas elsewhere that were told they never need to add chlorine or bromine to the spa, or add any chemicals at all! This is just not factual.

Ultra Violet Light Hot Tub Sanitation

The first alternative sanitizer solution we are going to look at is UV, or ultra violet light systems. We all know pretty much what UV light is, those rays from the sun that give you that sweet summer tan. Well, there are many frequency spectrum’s of UV light and certain spectrum’s of UV light are very destructive to living organisms.

The important thing to understand about UV is that it does not really kill anything. Instead the UV light scrambles the organisms DNA causing it to be inactive, which means it can’t reproduce. This makes any bacteria or virus that comes in contact with the UV light harmless.

Here is a nice snippet from Wikipedia:

UV will break the molecular bonds within micro-organismal DNA, producing thymine dimers in their DNA thereby destroying them, rendering them harmless or prohibiting growth and reproduction. It is a process similar to the UV effect of longer wavelengths (UVB) on humans, such as sunburn or sun glare. Micro-organisms have less protection from UV and cannot survive prolonged exposure to it.

Cons of UV Sanitation:

The one downside of UV is its limitation to only a certain frequency of the UV light spectrum. There are a lot of things that can disrupt the spectrum of light from contacting the organisms in the circulation system, something as simple as dust on the bulb itself can render the UV sanitation system pretty much useless.

Also sanitation relies on direct line of sight so the organisms are only destroyed when they come in direct contact with the UV. The circulation system in the hot tub makes it so eventually all the water (and whatever is in the water) does get exposed to the UV light multiple times of day. However this fact of direct contact is why there needs to be some level of residual sanitizer in the water at all times.

Ozone Sanitation Systems for Hot Tubs:

Ozone gas sanitation systems have been around in the hot tub industry a little longer than their UV counterparts. When we think of ozone we ironically think of the layer above our heads in the sky that protects us from UV radiation. However ozone gas or O3 is a powerful oxidizer used in many commercial and residential applications including hot tubs.

It is such a powerful oxidizer that it can oxidize and destroy any bacteria or pathogens it comes in contact with. The key there is WHAT IT COMES IN CONTACT WITH. Hot tub manufacturers design the ozone system so that the o3 gas is injected into the plumbing system and mixes with the circulated water. So as the pump is moving the water through the system it ends up mixing with the o3 gas and any particles or contaminants get oxidized and killed.

The other nice thing about ozone is that it can oxidize chloramines and bromines, which are the bad smelly irritating byproducts of chlorine and bromine. With a bromine sanitizer it actually turns used-up bad bromine (bromines) back into good use-able bromine, freeing it so it can sanitize the water again.

Your ozone Wikipedia snippet:

Ozone is used in homes and hot tubs to kill bacteria in the water and to reduce the amount of chlorine or bromine required by reactivating them to their free state. Since ozone does not remain in the water long enough, ozone by itself is ineffective at preventing cross-contamination among bathers and must be used in conjunction with halogens (chlorine or bromine).

Ozone Cons:

That last part about cross-contamination is true of both UV and ozone which is the reasoning behind the paragraph at the beginning of this article.

Also you will notice in that snippet ozone has a short half-life, it only lasts 15-30 seconds after production. That means the ozone system in a spa needs to be set up properly so it is injected into the system well before the water re-enters the main hot tub bather area.

Salt Water Hot Tub Sanitation:

The biggest misnomer about salt water sanitizers in pools or hot tubs is that it is a chlorine free system. In the store doing water test people always say to us, “I don’t use chlorine we have a salt water pool”. When the reality is they have a chlorine pool generated by salt.

What a salt generator does is splits salt into chlorine which immediately turns into hypoclorus acid, which is the strong sanitizer found in swimming pools and spas. It is the same exact effect as pouring liquid chlorine or bleach into the water, except in the case of a salt generator you are making your own chlorine.

When you have a salt system in your hot tub you eliminate the need for external chlorine granules or bromine tablets to maintain a sanitizer residual. However other water balancing chemicals are still needed in order to maintain the water clarity and the spa equipment longevity.

Salt Water Cons:

The best part about the previous systems, UV and Ozone is that we are able to lower the amount of chlorine or bromine that we need in our hot tub to keep it clean, whereas in a salt system it is all chlorine and you maintain a higher residual chlorine level than what is needed with an ozone or UV system.

The other downside of salt water sanitation is its corrosiveness to metals and other components in the hot tub. This is why it is very important that the water chemistry balance is kept perfect at all times with a salt generator as the system is very sensitive. This just means the water will need to be tested and adjusted a bit more than a non-salt system. Also the salt generator tends to push PH levels in the water up, and as PH rises chlorine becomes a less effective sanitizer so use of acid or granular PH down is needed regularly.

Salt Generator Wikipedia Snippet:

The benefits of salt systems in pools are the convenience and the constant delivery of pure chlorine-based sanitizer. The reduction of irritating chloramines versus traditional chlorinating methods and the “softening” effect of electrolysis reducing dissolved alkali minerals in the water are also perceived as benefits

Downsides are initial cost of the system, maintenance, and the cost of replacement cells. Salt is a corrosive and will damage some metals and some improperly-sealed stone. However, as the ideal saline concentration of a salt-chlorinated pool is very low (<3,500ppm, the threshold for human perception of salt by taste; seawater is about ten times this concentration), damage usually occurs due to improperly-maintained pool chemistry or improper maintenance of the electrolytic cell. Pool equipment manufacturers will not warranty stainless steel products damaged by saline pools.

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What system is best for my hot tub?

As you can see there are pros and cons to each system and there really is not one be all end all must have out there, they all work in their own way to help keep your hot tub water, safe, clean and clear. The most important thing to remember is none of these systems are set it and forget it. The water in your pool or spa should be tested and balanced regularly to help keep it sanitized and comfortable.

At Precision Pool our Marquis Spas use an Ozone based system with a mineral cartridge and bromine residual back up cartridge. It works great for us and we help guide our customers on the simplest methods to keep the water clear, safe and enjoyable all year round.

This is a long article and I am sure will answer some questions as well as create new ones, so please feel free to use the comments section to discuss and we will try to reply as quickly as possible.

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  1. Regina Peterson
    May 13, 2015 at 10:52 pm · Reply

    I have been looking into getting a saltwater pool because I grew up in California and I’m used to the ocean. I don’t like the feeling of chlorine on my skin and so that’s one of the biggest reasons. Are there any studies done that shows which systems are best for your skin?

  2. Matt
    August 4, 2015 at 7:46 pm · Reply

    What about Dead Sea Salt Water system for hot tubs (bromine generator instead of chlorine generator), that use sodium bromide salt instead of regular sodium chloride salt? You didn’t discuss that option, but I believe it is the best since there is no corrosion issues like with regular salt and since bromine works much better in hot water than chlorine (doesn’t turn to a vapor and isn’t rendered ineffective by pH fluctuations). It also requires less salt to be used, only produces the minimum amount of pure bromine you need (3-5 PPM) and doesn’t produce by-products or require other chemicals. Plus it makes the water feel AMAZING!

    • admin
      August 5, 2015 at 9:56 am · Reply

      Hi Matt,

      While I am with you that bromine is a much better sanitizer in hot tubs than chlorine for a number of “way too far in depth” chemical reasons, I have not yet had experience with the dead sea salt systems and bromine generation. I have read some interesting things though.


  3. K.
    December 4, 2015 at 1:56 pm · Reply

    Is the ozone produced by a ozone generator in the tub harmful to your health? Does it off gas from the water as you sit and breath it in? We are looking at buying a tub but have chemical sensitive and asthma in the family. Any suggestions?

    • admin
      December 4, 2015 at 2:00 pm · Reply

      Hi K.,

      The ozone mixes within the plumbing of the spa. Ozone has a short half life, so within 15 seconds it will convert back into oxygen. The bubbles coming from the bottom of the tub are just oxygen at that point. All the OZone contact takes place within the plumbing or in some systems a mixing chamber.


  4. Fay Marie
    March 27, 2017 at 2:19 pm · Reply

    I’m not sure you still monitor questions from this article but I’m going to write just in case you do. I am an advanced cancer patient using only alternative treatments, for the 2nd time in this battle. I am responsible for the care of the family home since my parents passed and it includes an in-ground pool and a hot tub. I am not able to use them as chlorine is extremely bad for all people and much worse for cancer patients. Is there a way to make these usable for myself without using these chemicals? It would be an excellent addition to the battle if I was able to get exercise with the pool that didn’t cause pain, and the heat thermia type assistance with the hot tub. I know many people in my situation that are also interested in this information. Thank you for your time.

    • admin
      March 28, 2017 at 2:59 pm · Reply

      Hi Fay,

      Sorry to hear about your battle, hope it all works out.

      Generally people have issues with the byproducts of chlorine due to the yo yo affect of adding a bunch, it using itself up and off gasing harmful chlorimine. So if we can keep chloromines under control we can keep people from having a bad reaction to breathign that in.

      A combination of ozone and uv on the pool with low doses of liquid chlorine once a week will definitely work in the inground pool. In the hot tub it may be tricky.

      This may be the only case where I would recommend a biguanide treatment like Baquaspa. I don’t usually like it as I don’t think it is as good a sanitizer as chlorine, but it works for instances like this.

  5. Bridget
    April 21, 2017 at 4:11 pm · Reply

    Really? Bromine? Have you even looked at the heath issues that arise with Bromine use? Thyroid Cancer for one and there are many other health issue that arise from the use of Bromine. Hot Tubs are meant to make you feel better not make you sick!

    • admin
      April 25, 2017 at 3:11 pm · Reply

      Hi Bridget,

      No matter what type of alternative sanitizers and oxidizers you hav einstalled you still need to use some type of “halogen sanitizer” like chlorine or bromine to prevent peer to peer transmission of contaminents there is no way around it.

      No as far as the health concerns, chloromines and bromines which are the offgassed byproduct of chlorine or bromine interacting with a contaminent in the water.

      If you have a build up of bromides and breath in that off gas that is not good. But this does not happen as the water is treated with regualar shock it oxidizes these bromides before they become an issue.

      Also when using things like ozone, uv, minerals, ect…the amount of free bromine or chlorine you need in the water is very low.

      Hope that helps,


  6. Melissa
    May 24, 2017 at 3:11 am · Reply

    My understanding is that if you choose a UV or Ozone system you still need a sanitizer system. Would the UV or Ozone work well with a salt water system? Also, I heard about a combo UV/Ozone system. How does this compare to the individual systems?

    • admin
      November 23, 2018 at 1:52 pm · Reply

      Yes combo systems are great. We do that in pools but hot tubs have not adopted that yet. The Endless Pool Fitness Systems we sell are the only ones I have seen that use both UV and ozone. Still need a residual chlorine, but not much at all.

  7. Gav
    October 24, 2017 at 1:14 am · Reply

    Hi, looking at replacing our existing old spa. My wife has psoriasis. Is there an opinion whether ozone or salt system would be better for her skin?

    • admin
      November 23, 2018 at 1:55 pm · Reply

      Skin irritation is usually due to imbalances in Ph and Alkalinity or build up of chloromines (used up chlorine).

      By using a oxidizer like ozone that helps keep chloromines down as it oxidizes them. Salt is just chlorine, however it is regulated so you get a more even dosing which keeps chlorimines down which ultimately leads to better feeling water.

  8. Stacy
    August 27, 2018 at 6:41 pm · Reply

    Thanks for the great article!

  9. johnson
    October 29, 2018 at 8:09 pm · Reply

    see lots of questions and zero answers

    • admin
      November 23, 2018 at 1:57 pm · Reply

      Hi there,

      As we are a brick and mortar company with a full service department it is not always possible to keep up with all the blog comments unfortunately. I would not say ZERO answers I see about a half dozen questions that we have replied to below also this article was written 3 years ago. unless of course this is a spam comment 😉


  10. Andy K
    December 24, 2018 at 8:14 pm · Reply

    Super informative. Thank you Jay! Just researching Hot tubs and came across this article. I was hesitant to read it due to age of article but it’s awesome that you have continued to answer questions!! Happy Holidays. Cheers.
    Andy K.

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