What is a Hot Tub Sanitizer and Which Sanitizer is the Best?

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A hot tub sanitizer kills bacteria and purifies the water. The sanitizer is the most critical component to a healthy hot tub experience.
Hot Tub Sanitizers

There are many sanitizers on the market. Some are great, some are mediocre and some are terrible. Below, I’ll take you through the different sanitizing options and the pros and cons of each.

Chlorine

Chlorine is the most widely used sanitizer for pools. Because it does not come in tablet form, it is not a suitable stand-alone sanitizer for spas, as the granules dissipate too quickly.

Chlorine is a great shock for hot tubs and is commonly used in conjunction with mineral sanitizers, burning off dead organic matter and preventing cloudy water.
Chlorine

Bromine

Bromine is the most widely used hot tub sanitizer. It comes in tablets which can be inserted into a floating bromine feeder and provide continuous sanitization to the water.

While very effective at killing bacteria, some people may have a sensitivity to bromine. Some individuals experience dry or irritated skin and find the chemical odor of bromine to be overwhelming.
BromineTablets

Cons of Chlorine & Bromine

Excessive use of halogen sanitizers (chlorine and bromine) can bleach and damage the underside of the spa cover, fade swim suits and even pit the hot tub shell.

 

Mineral Sanitizers

There are a couple “alternative hot tub sanitizers” on the market that use copper or silver ions to sanitize spa water. Many people switch to mineral sanitizers because they are odorless, more natural, and do not fade swimsuits or damage spa covers.

 

  • Cleanwater BlueCleanwater Blue is an EPA registered liquid bactericide/algaecide made from copper ions. These ions disrupt the cell structure of microorganisms, eliminating them in a safe way.

    The science behind Cleanwater Blue dates back to ancient times, when drinking water vessels were made from copper to help keep the water fresh. While crossing the plains, American settlers often put copper pennies into their water barrels to prevent stagnation.

Cleanwater Blue Sanitizer

  • Nature 2Nature 2 is an EPA Registered cartridge containing silver minerals, which you can put in your filter cartridge or in the filter housing. As water passes through the Nature 2 cartridge, positively charged silver ions disperse in the water, and destroy negatively charged cells of microorganisms.

    Like Cleanwater Blue, this systems is a great alternative for people who have a bromine sensitivity and is comparable in price.

Nature2 Mineral Sanitizer

Cons of Mineral Sanitizers

While there are no major cons to using mineral sanitizers, using test strips with these systems can be somewhat tricky. To date, there is no practical way for users to test silver ion content, so care must be taken to follow dosage instructions.

Bromine/Chlorine + Mineral Sanitizers

 

  • Spa Frog Spa Frog sanitizing systems combine minerals and a small amount of bromine to achieve sanitization in hot tub water. By incorporating minerals, the amount of bromine needed is greatly reduced.

    Spa Frog systems are a great option for people that like the test-ability of bromine and the benefits of mineral sanitizers.

Spa Frog Mineral Sanitizer

  • PoolRXDespite its name, PoolRX is a great mineral sanitizer for spas. This product works synergistically with a constant low level of chlorine.

Pool RX

Ozonators

Ozonators, or ozone generators, are add-on components in hot tubs that distribute ozone through the air lines. Ozone works to break down contaminants in hot tubs by oxidization, destroying bacteria, soap residues and other undesirable particulate on contact.  Ozone also frees up spent chlorine and bromine particles, enabling them to be reused again and again and allowing you to use far less chemicals to maintain sanitization.

Ozone has a very short half-life in water (about 15 minutes) and must be used in conjunction with a sanitizing agent, such as Bromine, Cleanwater Blue or Nature 2.
Aqua Sun Ozone

Cons of Ozone

Excessive ozone can cause damage to the underside of spa covers and thermal blankets.

Salt Systems

Saltwater based systems, such as the Saltron Mini, generate chlorine by passing a mild electric current through salt water. Salt, which is added to the spa water, is the source of the chlorine which acts as the sanitizer with this system.
Salt Systems

The ease of use with these systems makes them very popular. Many people also experience softer, more moisturized skin after soaking in a hot tub equipped with a salt system.

The low salinity level required with these systems does not corrode spa equipment.

 

Cons of Salt Systems

The cells which generate the chlorine require some cleaning maintenance.

Biguanides

Biguanide sanitizers are commonly hydrogen peroxide based and require proprietary companion water balancing products.

 

Cons of Biguanide Sanitizers

Biguanides are known to erode certain plastic components, such as jets, causing them to no longer stay in place. Biguanides and their proprietary companion components are significantly more expensive than most other sanitizing systems. Many people report coughing and burning sensations in the lungs and eyes after inhaling steam in hot tubs treated with biguanide sanitizers. Hydrogen Peroxide can be dangerous to store, handle and transport. Biguanide sanitizers often fail to prevent algae slime.

Mystery Ingredient Systems

There are several mystery ingredient “water treatments” on the market which claim that you can “throw away all of your other chemicals” and “use this product and never test your water again”.

Beware! These products survive by using irresponsible and dangerous marketing. The small print on these products state that they do not kill bacteria.  The truth is that these products are mostly comprised of dissolved salts in water. Truly not worth the $100+ price tag.
Silk Balance

If it sounds too good to be true, it usually is.

So, Which is the Best?

It is clear that mineral systems are gaining huge popularity. Being that they are odorless, gentle on the skin and hot tub equipment, and comparable in price to chlorine/bromine sanitizing systems, it’s not hard to understand why.

Do you have questions about your hot tub water maintenance? Comment below for expert assistance!

39 comments

  1. we ordered the Nature 2 mineral cartridge from your company. we are also using the spa sanitizer granules. is how we are supposed to be using it. we bought the kit. feed back would be appreciated . have 6 pounds of bromine but do not want to use it.. due to reading about the effects bromine can have on the health of a person. thanks

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  2. I use Bromine but have found by using a filter when filling the water stays better much longer and chemical use is minimal! Saves lots of money

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  3. We currently us chlorine and Nature 2 for our hot tub. My husband has a sensitive skin issue and is sometimes bothered by the hot tub. I am thinking about switching to the Cleanwater Blue system. If I do should I also continue to use the Nature 2 or is it not necessary with Cleanwater Blue?

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  4. Hi Cindy,
    Thank you for your comment. Once you switch to the Cleanwater Blue, you no longer need to use the Nature 2 Cartridge, and the CleanWater Blue (blue box) is also a mineral sanitizer.
    Some skin sensitivity may also result for low or high pH levels, so be sure to test and balance these every other week with the Cleanwater Blue system.
    Please let me know if you have any additional questions.
    Thank you,
    Kaisa
    SpaDepot.com

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  5. Hi Sharon,
    Thank you for your comment.
    Yes, Sanitizing Granules are compatible (when used as an occasional shock) with the Nature 2 system. You don’t want to use bromine with Nature 2.
    Here is a link to the Nature 2 maintenance tips & instructions: http://www.spadepot.com/docs/KT1005.pdf
    Please let me know if you have any additional questions.
    Thank you,
    Kaisa
    SpaDepot.com

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  6. hi I’m using the natures 2 in my hot tub ,now that summer’s coming around wanted to know if we could turn the temperature way down and just use the Jets so more less trying to say no hot water just jets what do I need to use to keep the water sanitized

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  7. Hi Misty,
    You can turn the hot tub down to the lowest setting and use the jets. The lowest setting is probably going to be around 85 degrees F. Once the temperature in the tub gets lower than 85 degrees, the jets will turn off while the tub heats back up to the setting.
    I hope this is helpful. Please let me know if you have any additional questions.
    Thank you,
    Kaisa
    SpaDepot.com

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  8. Nice information on hot tub sanitizers. I have done swimming and in my pool they mostly use Chlorine as sanitizer, I was not aware that there are other options. I always have a bath have contact with swimming pool water because I don’t want Chlorine to effect my skin. But I don’t swim so often just once a while.

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  9. Hi, I use chlorine granules and Nature2 in my Tiger River spa. I’ll be out of town for a couple weeks, and I thought I heard somewhere that a good idea is to drop a chlorine tablet into the filter tube (where I put the Nature2, just above it), so it will dissolve slowly while I’m gone. But the tablets you sell are Trichlore, and the description says they are not recommended for spas.
    Do you it’s a good idea nevertheless, or is there a better way? Or is there such a thing as regular chlorine tablets (maybe I’m not searching correctly)?
    Thanks! –Larry

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  10. Hi Larry,
    Thank you for your comment, I’m happy to help!
    You never want to use Trichlor in a hot tub, as it will destroy spa plumbing and equipment (it is intended for larger pools). However, you can use Bromine Tablets in a floating feeder:
    http://www.spadepot.com/shop/Bromine-Tablets-15-lbs-P607C43.aspx
    http://www.spadepot.com/shop/Floating-Bromine-Chlorine-Dispenser-Feeder-P609C43.aspx
    Once you return, you will just want to test and balance your water as usual. You may need to add a little bit more Oxy Spa Oxidizing Shock than normal.
    I hope this is helpful. Please let me know if you have any additional questions.
    Thank you,
    Kaisa
    SpaDepot.com

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  11. I have an Infinity spay that is 12 years old. have been using chlorine and hate it, so I don’t use it as soften as I’d like to. I was thinking of swtching to saline purifiying, but was told it would ruin my piping ,etc. Is the saline safe for the equipment? Also, what would you recommend, the hot tub holds less than 700 gallons of water.
    thanks
    susan

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  12. Hi Susan,
    Thank you for your comment. I’m happy to help!
    Salt systems work by converting salt to natural chlorine, so if it’s the chlorine aspect you don’t like, I would recommend switching to a mineral sanitizer. Lots of folks who dislike chlorine and bromine really like the Cleanwater Blue or Nature 2 systems.
    Spa grade chlorine does not come in tablet form, and the granules dissipate too quickly to be effective, so chlorine is not considered to be an effective stand-alone sanitizer for hot tubs. Pool grade chlorine (trichlor) which does come in tablet form is far too potent to use in hot tubs, as it will damage the plumbing and equipment.
    Bromine is a good alternative if you like the effectiveness of spa chlorine, but are looking to decrease time spent maintaining the water.
    I hope this is helpful. Please let me know what additional questions you have.
    Thank you,
    Kaisa
    SpaDepot.com

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  13. I changed to the Cleanwater Blue system on you recommendation about a month ago. I have had nothing but problems with it. The chemistry gets out of whack ecery couple of days. The water gets cloudy every other day. Even though I haven’t put any of the Cleanwater Blue liquid in since the first day, the test strips show high levels of copper. I’m at my wits end — about ready to toss it for something else. It doesn’t seem to work. What am I doing wrong. The test strips for the copper level are always grey. And I’m changing the filter twice a week because it turns green. .?????

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  14. Hi Skipper,
    I’m sorry you are having issues with the Cleanwater Blue system! It can be a very easy to use system, but there is a bit of a learning curve when you first start up.
    The greenish tint to the filter is a symptom that the copper is coming out of solution, which can be from either pH and Alkalinity being out of balance, or too much copper, or a combination of both. With the CWB system, it’s very important that the pH and Alkalinity are balanced before you add anything else to the water, since the Cleanwater Blue locks the pH and Alkalinity in place. If the water is not balanced, it can cause the copper to come out of solution and cause cloudiness, and it is very difficult to balance the water after the copper is added.
    The easiest solution would be to drain a foot or two of water out of your tub and refill with fresh water. If using well water, be sure to use a hose-end filter that removes any excess minerals or metals that may make balancing your water difficult. You can then adjust your pH and Alkalinity to the correct range and test for copper again, adding the amount suggested on the quick-start guide. Be sure to shock after every time you get out with the Oxy-Spa non-chlorine shock, and if you have occasional cloudiness you can always add a small dose of the Spa Sanitizing granules (dichlor).
    I hope this helps, and if you have any more issues, we’re happy to troubleshoot with you!
    Thanks,
    Bonni
    SpaDepot.com

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  15. Hi Spadepot, I just purchased a Coleman Lay-z-spa and have been reading this blog about water treatment. I am sooooo lost!!! Bromine, Chlorine, etc. Can you recommend a water treatment regimen (chemicals, test strips, etc) for this type of spa? I’m looking for the easiest and least time consuming methods to treat the water. I purchased Leisure brand bromine tablets along with the spa, but after reading this blog, I’m just not sure how to even begin treating the water, much less maintaining it in the most efficient, effective and safest way. Please help. I need the total package and I’m ready to order!

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  16. Hi Claude,
    Thank you for your comment. For the least amount of maintenance and testing, we recommend the Clearwater Blue system. This sanitizing program only requires bi-weekly testing and balance, as opposed to the weekly required by most other sanitizers. It is also extremely effective.
    Here’s a link to the start-up kit which includes everything you need for this system and comes with thorough step-by-step instructions: http://www.spadepot.com/shop/Cleanwater-Blue-Pro-Supplies-Kit-P438C67.aspx
    I hope this is helpful. Please let me know if you have any additional questions.
    Thank you,
    Kaisa

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  17. We used the flush to clean the spa out two times after it had been sitting for six months waiting for a blower repair. Now we cannot get a salt like buildup on the shell to come off. You wipe it down and next day it is back. I put new filters, use your balancing products and no positive results.
    It is a white, salty like buildup. Feels almost like sand on the sides and bottom of the spa.

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  18. Hi Tonya,
    Thank you for your comment. I’m happy to help!
    You’re experiencing minerals that have come out of solution, most likely calcium. Are you on well water?
    To remove the scale you’ll want to use a calcium sequestrate, such as Spa Defense: http://www.spadepot.com/shop/Spa-Defense-32-oz-P9184C635.aspx
    You can also use a Pre-Fresh Hose End Filter to prevent this during your next refill: http://www.spadepot.com/shop/PreFresh-Spa-Pool-Water-Fill-Filter-P784C632.aspx
    You can use a little bit of Spa System Flush on a rag to remove the scale that is clinging to the spa shell.
    I hope this is helpful. Please let me know if you have any additional questions.
    Thank you,
    Kaisa
    SpaDepot.com

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  19. My wife and I just got a new hot tub and are learning about the chemicals, when we use the test strips we have been getting high MPS reading it’s very purple what can you do to reduce the MPS or is it not to be worrying about?

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  20. We have a Hot Springs spa that we just switched over to the Cleanwater blue system. We were using the Hot Springs system which used a continuous silver ion sanitizer thing in one of the filters. Should we remove it or continue to use the silver ion sanitizer?

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  21. Hi Dan,
    Thank you for your post. You’ll only need the Cleanwater Blue system, as it is a complete sanitizer. There is no need to use both systems at the same time, and you may run into compatibility issues if you do.
    I hope this is helpful. Please let me know if you have any additional questions.
    Thank you,
    Kaisa

    Like

  22. WE purchased this : Aqua Sun XL-80 Universal Ultra Long Life CD Ozone System with Injector 120/240V I have a dual speed pump.My question is does this unit only dispense ozone when needed because it shuts off at high speed??

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  23. Hi Debbie,
    Thank you for your post. The ozonator only runs during your automatic filtration cycle, so if the spa is switched to another mode, the ozonator will automatically shut off. No harm is done, the ozonator will turn on again when your spa goes back into filtration mode.
    Please let me know if you have any additional questions.
    Thank you,
    Kaisa

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  24. We are using the Nature 2 cartridges and adding your OxySpa MPS after each use with a chlorine shock once a week in our Bullfrog hot tub. We have heard that we need to leave our spa cover off for 20 minutes after adding chlorine. Living in a northern climate, we try to not leave our cover open more than necessary. My question is when we add the MPS after each use can we shut the cover immediately or do we have to leave it open for a period of time? Does having an ozonator make a difference with being able to shut the lid for these oxidizers?

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  25. Hi John,
    Thank you for checking with us! It is a good idea to leave the cover off after adding both chlorine and Oxy Spa to the spa water. Leaving the cover off every time will certainly prolong the lifetime of your cover. I recommend leaving the cover off for 10-15 minutes after adding chlorine or Oxy Spa. You might also consider getting a ThermoFloat Spa Blanket. ThermoFloat Blankets prevent evaporation, so they’ll not only help right after you add chemicals, they will help prevent evaporation into the cover when the cover is on. We have them available here:
    http://www.spadepot.com/shop/Floating-Blankets-Coveralls-C637.aspx
    I hope this helps! Please let me know if you have any other questions.
    Thanks,
    Mark
    SpaDepot.com

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  26. Thanks Mark. The floating blanket looks like a good idea for saving energy and protecting the cover. I am disappointed to learn that the Oxy Spa will damage the cover like chlorine if I shut it right after its added. That adds up to a lot of extra time uncovered when it is below freezing outside. Does the Oxy Spa not work as well in a hot tub that is covered?

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  27. Hi John,
    I appreciate you checking back with me, and that is a good question. Leaving your cover off after you add chemicals, any chemicals, is only to help increase the longevity of the cover. That’s really it. If you added chemicals and immediately closed the cover, any off-gasses from the chemicals are going to sit between the water and the cover. If you use the proper amount of chemicals and keep your water balanced, closing your cover right after you add chemicals is only going to slightly shorten the life of the cover. There are lots of hot tub owners that close their covers right after adding chemicals, and their covers lasts more than 10 years. There are also hot tub owners out there that don’t balance their water, use way too much sanitizer and ruin a brand new cover in less than one year.
    Considering the potential heat loss in the winter, I would actually recommend putting your cover right back on in cold weather, and leaving it off for a few minutes during the warmer months. As long as you keep everything balanced and use the ThermoFloat Blanket, your cover will last many, many years.
    Please let me know if you have any other questions!
    Thanks again,
    Mark
    SpaDepot.com

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  28. I want to switch my spa from chlorine to Cleanwater blue. Do I need to drain the tub and fill with clean water to make this switch??

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  29. If you are Using chlorine and the nature to stick. Can you use a bromine floater while you’re out of town? Is that what you were saying to Larry? I have the same question So just wanted to make sure I understood your answer. I did not think you could mix chlorine and bromineLike that.

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  30. Hi Debby,
    I’m sorry for what seems like conflicting information! You should always use bromine instead of trichlor tablets, since trichlor is meant for pools and is too strong. But while the Nature 2 cartridge is inserted, only dichlor chlorine or non-chlorine shock should be used since bromine can coat the silver ions in the cartridge.
    As far as treating the spa when you are on vacation, you can give the water a shock with dichlor before you leave and shock again when you get back, and the Nature 2 cartridge should do the rest. Turning down the heat a bit will also encourage cleaner water since microbes love hot water.
    Thanks,
    Sarah
    SpaDepot.com

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  31. Help! Started using a Saltron about 18 months ago with mineral salts. Have always had the salt level and Saltron settings to keep water normal. Have never had to add additional salt. Spa is used maybe once a week. Test and adjust for PH etc at least whenever spa is used. The blue plastic edges of my spa filter are dissolving and I noticed my plastic headrests are rough at the water line. My jets are flying off right and left with plastic corrosion issues. My heater died and has since been replaced. I removed all the water and refilled and am awaiting a new filter and jets to be shipped. What on earth caused all these problems? I have owned spas for over 30 years and have never seen anything like this. Is this due to the salt water?

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  32. Hi Amy,
    It sounds like your chlorine time may be set too high, since high levels of chlorine degrade plastic. I would recommend testing to see how much chlorine is in the spa on a regular basis, and adjusting the chlorine time based on the test strip.
    Thank you,
    Sarah
    SpaDepot.com

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  33. Woo Hoo, our new hot tub will be here Friday. Already loaded-up on the Nature 2 cartridges. The spa dealer said the spa comes with a starter kit, and we can’t wait for our new ‘party pond’!

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  34. I purchased my Hot Tub new around 4months ago. After approx 1 month I was using with Wife and daughter and afterwards we all got an infection. Spots and Swollen lymph nodes under arms. I thought I had been following the instructions but decided to start again so after the infection subsided we dumped the water and started again this time making sure I was following the instructions more closely. Again a few weeks later myself and my wife got the infection back. Whats going on? The tub is 1000 ltrs, using nature stick and Lithium @ 1 teaspoon per bather each use. Shock once a week and pressure clean the filters. PH in range. Most recent event there was a little foam but not much. Can anyone offer any suggestions? I’m usually the only one in and everyone else is too scared now and I shower before going in to make sure the TDS is keppt as low as possble. Please any assistance would be appreciated.

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  35. Hi,
    I’m sorry you are having so much trouble with your spa! First, we would recommend doing a complete spa decontamination. This will not only start you off with fresh water, but clean out your plumbing, which can harbor harmful microbes. Read our instructions for decontaminating here:
    http://www.spadepot.com/spacyclopedia/spa-contamination.htm
    One more note: Lithium is not the best choice of chlorine to add to a spa. Lithium hypochlorite is not stabilized, has a high pH, and is a less concentrated amount of chlorine than granular dichlor, the only chlorine recommended for hot tubs. In the future, you may want to switch to dichlor to better keep up with the hot, high bather load environment of a hot tub.
    I hope we can get your hot tub under control again soon! Let me know if you have any further questions.
    Thanks,
    Sarah
    SpaDepot.com

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