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).”
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.”
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.