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Hot Tub Chemicals How To Guide

An easy introduction to spa chemicals.

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Here's a hot tub water chemistry primer that should help clarify what actually goes on in the mysterious soup that is your hot tub water. If you just want to know what to do about a specific problem you're having, please go to our handy Spa Water Troubleshooting page. But if you are seeking true hot tub enlightenment, please read on...

If your experience was anything like ours, the most confusing thing about owning a spa is dealing with hot tub chemicals that are required to do a whole bunch of seemingly complicated things. There are sanitizers, shock, pH balancers, test strips, water cleaners, filter cleaners and you name it. They all do different things except for chlorine, bromine, minerals and ozone which all do the same thing...only differently, which leads us to...

"The most important thing"


We know an expert in our business who says, "on a scale of one to ten, using a sanitizer in your hot tub is a "ten" and everything else begins at around a three." Our friend tends to exaggerate for effect, but he's got a point. Sanitizing your spa water is the most important spa maintenance you can do for yourself. Why? Because sanitizers kill the bacteria and viruses that populate every hot tub (that's right Mr. Clean, even your spa). Put bluntly, you don't take a soak in an un-sanitized hot tub for the same reasons you don't stick your head in a toilet (yes, we know, but just because your friends think you should do it doesn't mean you should). Got the picture? Ok, so here's a quick run down on the different types of hot tub sanitizers:

  • Chlorine GranulesChlorine: You're probably familiar with Chlorine as the primary sanitizer used in pools. You can use chlorine safely in spas too, except in a different concentration. There are chlorine tablets and chlorine granules created specifically for hot tub use.

  • Brominating TabletsBromine: Bromine tablets are a combination of sodium bromide and chlorine. Many people choose bromine over chlorine because the smell is not as strong. Bromine is available in tablets and is generally distributed using a floating feeder.

  • Mineral Purifiers: You can use mineral purifiers to assist (but not entirely replace) your sanitizers in keeping your hot tub clear of contamination. Mineral purifiers are typically placed inside your filter cartridge or contained in a floating dispenser and the sanitizing minerals are slowly released into the water over time. We at the HotTubWorks like to use Spa Frog mineral purifiers in our spas for three reasons:
    1. They're really easy to use
    2. They really work
    3. They radically reduce the need for harsher chemicals like bromine or chlorine.
    Check out our Spa Frog products section for this excellent "on board" sanitizing alternative. If you have a Hot Spring Spa, you may want to use their mineral product the Hot Spring Freshwater AG+ Continuous Silver Ion Purifier.

  • Ozone: Ozone sanitation requires that your hot tub is equipped with a piece of equipment called an "ozonator." Even if your spa has an ozonator, you will need to supplement your spa water with a low level of sanitizer like Bromine (and please don't let anyone tell you otherwise. The idea that a spa can be thoroughly sanitized with ozone or and/or mineral products alone is a myth).

  • Important: before adding any sanitizing agent to your hot tub, you must first test the current levels by using a water test strip.

    Test StripsThese strips are easy to use and formulated to measure the level of bromine and chlorine in your hot tub water along with your pH levels (see below). Depending on whether you use chlorine or bromine, you should add your sanitizing agents as indicated by the test strip and the instructions on the sanitizer you are using.

    See the Simple Spa Cleaning Program for a good example of a total spa maintenance program.


Before we leave the topic of sanitizers, we'll add another sentence or so to our friend's thoughts on keeping your spa sanitary.

Pop Quiz:
How often do you change your hot tub water?

  1. Immediately after your stinky relatives leave.
  2. When the moon is in the seventh house and Jupiter aligns with Mars.
  3. Whenever the water turns from that sort-of light brown color to that really dark brown color.

The second most important thing you can do for you and your hot tub is to CHANGE YOUR WATER about every three to four months. We know it's a pain in the butt but the reason why most hot tub manufacturers recommend it is that no amount of chemicals can protect you completely in water that is really old and dirty. Hey, you wouldn't wash your dishes in year-old dishwater would you? Well, there ya go. So next time you find yourself sitting around watching yet another Gilligan's Island episode while mouthing the dialogue from memory and eating something really bad for you, try tearing yourself away for a few minutes to change your hot tub water. You and your guests (should you still have any) will be glad you did!

Other Important Stuff
The following items are important, just not as important as your sanitizer.

  • Non-chlorine ShockShock: No we're not talking about your reaction to your property tax bill; we're talking about a very useful product that oxidizes the water and helps to get rid of dead organic matter like dead skin (think: bacteria buffet) skin oils, cosmetics and lotions. Shocking your hot tub weekly starves bacteria and helps prevent all that ugly dead stuff from clouding up your water and clogging your system.


  • pH Balancer pH: Ok, let's start with the obvious question. What is pH? Water pH is a measurement of the concentration of hydrogen ions in your hot tub water. Without getting into a freshman chemistry lesson, let's just say that pH is important because if you don't keep the pH levels within a small range (7.2-7.8), your water can become too alkaline or too acidic. If your ph is too low (less than 7.2), the water is too acidic and it can corrode parts of your hot tub and irritate parts of yourself (like your skin). If your hot tub water is above 7.8, it is too alkaline which can cause "scaling" from minerals and metals in your water forming deposits and possibly stains on your spa's acrylic surface. So, how do you know if your pH is in the right zone? First, as mentioned above, you need to test your water using an AquaChek test strip. Then, use chemicals such as Liquid Spa Up or Liquid Spa Down to achieve the right pH balance for your hot tub. When you change your water, you can add pH Balance Plus to achieve and maintain the right pH Balance until the next time you change your water.


Even More Stuff
Ok, so far we've covered the most important stuff, hot tub sanitizing, shocking and pH balancing but there are other useful concoctions you should use in your hot tub if they are needed. Here's a list:

  • Spa DefenderCalcium Hardness: If you live in an area with particularly "hard" OR "soft" water, it's worth checking your water calcium levels with your test strip and adjusting them if necessary. You can adjust your calcium levels up with Calcium Booster for water that is low in calcium and you can use Spa Defender if the calcium level is too high (which often causes cloudy water).

  • Alkalinity control: Total alkalinity refers to the ability of the hot tub water to resist changes in pH. Controlling alkalinity can help keep your pH in the appropriate range thereby lessening the need for pH balancing. If your AquaChek test strip indicates a need, you can lower Alkalinity using Spa Down (just like lowering your pH only you'll use smaller amounts). Or, if you need more alkalinity, you can use Alkalinity Increaser.

  • Metal GonHeavy Metal: Some local water contains unusual amounts of iron or copper. A greenish tint in your hot tub water may indicate the presence of these metals. If this should be the case in your area, resist the temptation to file for mining rights. These pesky metals can stain your hot tub shell and foul up your spa's water heater among other things. Fortunately, you can control metals by adding Metal Gon when you change your hot tub water, which, if you're anything like most of us, you don't do nearly as often as you should.



For Cleaning Your Hot Tub Filter
As we mentioned in our Hot Tub and Spa Filters section, it's very important to keep your hot tub filter clean and it's something your should do at least monthly. Of course, the easiest way to keep a clean filter is to replace it with a new one. Frankly, that's the solution we like best since we make more money on a filter than on a bottle of filter cleaner. However, we'd like to keep you as our customer, so we recommend that you clean your filter with a good cleaner a few times before it gets so gnarly you need to toss it out. Chances are the filter will last longer and you'll thank us by ordering a filter from us when you really need a new one. Here's how to find out when you need a new filter. Here's what to use when you want to clean one:

Cartridge CleanerSpa Instant Cartridge Clean is a spray-on cleaner for cleaning without overnight soaking.

Filter Clean is for use when you have time for overnight soaking (less elbow grease needed).

Just remember to cut the electricity off when your filter is out of the hot tub overnight to avoid letting impurities into your pump while the filter is out. Also, if you can, let your filter dry out before replacing it in your hot tub. This allows the filter material to expand and fluff up providing a more effective cleaning area.

For preventing the dreaded Hot Tub Scum Ring
When you're trying to impress that special friend, nothing says "class act" more than a dark scummy ring around your spa's water line. Unless the object is to keep everyone else out of your hot tub, it's time to get rid of that ring, or better yet, prevent it from forming in the first place! The first line of defense is an additive like Leisure Time's Enzyme. It helps prevent the build-up of oils and greases that combine to form the dreaded scum ring. If it's too late and you're already a scum victim, use the Citribrite Multi-Purpose Cleaner and a Tub Rub pad.

For Cleaning Your Spa

Cover CareCover Care and Conditioner: This product is good for cleaning, restoring and protecting your hot tub cover (or, if you'd prefer, we'd be happy to sell you a new spa cover).

Citribrite Multi-Purpose Cleaner: This is your basic hot tub shell cleaner. It helps get grease and grime off hot tub surfaces. It's so good that some of us around here use it for all our tough cleaning jobs. We've found it will clean most anything!


We hope this little section has cleared up a few things for you. For further reference, we invite you to download our exclusive Spa Chemical Trouble Shooting Guide and our Simple Spa Care Guide.

Note: this file is an Adobe Acrobat (PDF) file. If your computer was made sometime during this century, you probably have the software to open this file. If the file doesn't open after it downloads, click here to get the free Acrobat plug-in.

The main thing is to be aware of the fact that a hot tub does not maintain itself. It's up to you. Meanwhile, please let us know if you have any special tips or ideas for this section that we might use in the future. We're always looking for ways to let others do our work for us so we can take off early and enjoy more hot tub time!

Happy Home Hot Tub Life!

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