Spa & Hot Tub Chemicals for Dummies

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In today's post, we follow up on our popular Beginner's Guide to Spa & Hot Tub Care, and get more granular with our newest installment: Spa Chemicals for Dummies.

The book pictured is not a real book - not one that you can purchase, anyway. And by no means am I calling our blog readers dummies; it's just a fun title used for an in-depth informative guide on using hot tub chemicals. Because such a book does not exist, this post will explore some basic hot water chemistry topics that may confuse a novice hot tub owner.

Subjects like how to test water, what chemicals are needed for a hot tub, how to treat common water problems, as well as info about alternative sanitizers like ozone and minerals will all be included in this blog post.

So, without further ado, here's our in-depth guide to hot tub chemistry. Or, as we like to call it, Spa Chemicals for Dummies!

Types of Spa Chemicals

We carry more than 100 different spa and hot tub chemicals in our online store. No wonder it can be so confusing for new hot tub owners! To help make it easier, we've broken this section down into six categories of chemicals, each with a short description of what they are, when they're used and for what purpose.

Balancers: Spa chemistry is not overly complicated. When I speak about "water balance" and balancing chemicals, some people's eyes glaze over, but it's really quite simple! Balanced spa water is simply when your spa chemical readings are all within the proper ranges. Specifically, we want chemical ranges for pH at 7.4-7.6, total alkalinity at 80-120 ppm and calcium hardness at 150-250 ppm. When all three are within range, your water is balanced. If you really want to geek out and determine more accurate water balance, you can use a Saturation Index calculator. Of all spa balancing chemicals, pH reducer is probably the most commonly used. This is because pH and alkalinity tend to rise in spa water, and a pH decreaser effectively reduces both. If spa water is soft or you're noticing low hardness levels, raise it with a calcium booster. For a low pH and/or alkalinity test, use a pH increaser and/or alkalinity increaser to raise the levels.

Clarifiers: If your spa water is cloudy and lacks clarity or sparkle, it may be time for a new spa filter cartridge. If the filter is fine, there may be issues with water sanitation. Clarifiers are polymers that have a positive charge and attach themselves to negatively charged water particles floating around the hot tub. What starts as a microscopic particle eventually ends up as a large clump of hundreds of particles, large enough to get trapped in the filter. That said, clarifier chemicals are used for spa filters that need a little help, or when water conditions turn poor. Be careful not to overdose with clarifier however, or it may have the opposite effect and gum up your spa filter. If your hot tub water is always clear and sparkling, you may have no need to use a clarifier chemical.

Cleaners: In this category of spa chemicals, we have cleaning chemicals for your spa filter cartridges, cleaner and conditioner for your spa cover, cleaning and polishing products for your spa shell, as well as Jet Clean to purge biofilm buildup from your plumbing lines. Generally speaking, you should NEVER use household chemicals to clean your spa or accessory items. The only exception to this rule is using a mild soap, but only if you rinse it thoroughly afterwards to prevent the spa from foaming. In my own spa, I use filter cleaner, spa cover conditioner (my tub gets a lot of direct sun), and I use Jet Clean once or twice per year to prevent buildup in the pipes.

Sanitizers: sanitizer is the everyday chemical used to kill pathogens like bacteria, fungus, mold, viruses, etc. Most spa owners will use either bromine or chlorine as the main sanitizer. Granular chlorine is hand-fed when chlorine is preferred, or you can use bromine tablets, which is usually the easiest route. You can also use sodium bromide (a.k.a. bromine booster) and then a small amount of spa shock (either chlorine or MPS) to activate the bromide salts into bromine. Never use chlorine tablets in a spa, as they're formulated for use in swimming pools and are often too strong for spas; doing so could damage spa surfaces and equipment. You must keep an active level of sanitizer at all times in spas and hot tubs - about 2-4 ppm bromine or 1-3 ppm chlorine. If the level drops below the recommended range or near zero, pathogens, algae and other contaminants will begin to grow and multiply quickly, even in hot water and even when covered tightly.

Shocks: Spa shock is also a type of sanitizer, but it's used differently than normal spa sanitizers. Chlorine and non-chlorine (MPS) spa shocks are quick dissolving and fast acting. Shock is used to kill anything that your daily sanitizer has missed, or it can be used to supplement your daily sanitizer, such as after a four-person soak in the spa. Spa shocks are also used to activate bromide salts and convert them into bromine. If you use bromine tablets, this isn't necessary. But shock is still useful for giving the spa a sanitizer boost after heavy use, or as a regular weekly or biweekly shock treatment just to be sure the water is sanitary. Another use of spa shocks is to kill algae, remove foul odors, correct water discoloration or poor clarity, or resolve a variety of water issues from many causes. For best results, always check water balance and adjust as necessary before shocking a spa. Follow label instructions for treatment info and dosage to match your spa size in gallons/liters.

Specialty: Specialty spa chemicals are chemicals that don't fit neatly into the other categories. Chemicals like Foam Down or Foam Out (removes surface foam), Metal Gon/Defender (keeps metals and dissolved solids in solution), enzymes like Natural Clear (dissolves oils naturally), algaecides (prevents algae growth in hot water spas) or Leak Seal (seals up small leaks) all fit into this catch-all category. You may have some need for these chemicals at some point to resolve water-related issues in your spa. Then again, you may be lucky and only rarely need specialty chemicals. Some people also group aromatherapy products into the specialty chemicals category, but these are not for correcting a water balance or hot tub issue. Aromatherapy is for YOUR benefit, and can be used anytime you settle in for a soak. At least when you need specialty chemicals, you'll know where to find them!

How To Test Spa Chemistry

There are two ways to test hot tub water - with test strips or with a test kit. Unless you fancy yourself a chemist and prefer to use a titration test each time, I usually recommend multi-purpose test strips, which test for all the important stuff in just one to two minutes. The secret to spa chemistry is not sold in a bottle, but it is pretty simple. Just test your spa water two or three times per week with regularity, and adjust in small increments as needed. You will begin to see patterns in the water's chemical fluctuations, especially if you keep a test log book. Even if you don't write down your readings or enter them into an app, over time you'll come to know your own hot tub's chemical personality.

How To Store Hot Tub Chemicals

  1. Keep out of reach of children.
  2. Store in cool, dry location at 50-80° F.
  3. Only open one container at a time.
  4. Tight lids keep out moisture, children and prevent spills.
  5. Protect chemicals from spills, mixing and contamination.

We've covered the topic before with some neat spa chemical storage ideas, but the general idea is to, number one, keep out of reach of children. Secondly, store spa chemicals in a cool, dry location, which usually means indoors. Temperatures of 50-75° F are best for prolonging chemical shelf life, helping to prevent gas formation or the hardening of granules. Always open, use, and tightly close only one chemical at a time. Tight lids keep out moisture and small children, and also prevents spills, accidental mixing or contamination. Very important tip: never allow spa chemicals to mix with each other or become contaminated with any substance (dirt, leaves, etc.). A fire or explosion could result. Also, don't hang onto old spa chemicals; use them up or dispose of them. If you live in an earthquake zone, it's recommended to keep chemicals close to the ground, and not high on a shelf where they may fall and spill their contents. Again, make sure children can't access these chemicals.

What Chemicals Do I Need for a Spa or Hot Tub?

  1. Spa sanitizer - usually bromine or chlorine
  2. Spa pH increaser and decreaser
  3. Spa alkalinity increaser
  4. Spa calcium hardness increaser
  5. Spa shock - either chlorine or MPS

As a minimum, you'll need most of these spa chemicals. You'll likely use pH reducer more often than pH increaser, and probably adjusting the levels two or three times per month. Total alkalinity and calcium levels will usually hold steady for a month or more once it has been adjusted after a spa drain and refill. Spa shock will be needed for weekly use, in addition to a regular spa sanitizer for daily use. You may also have a need for other chemicals from time to time such as filter cleaners, metal removers or clarifiers. Many of our customers like the convenience of our Spa Care Kits, which are complete 6-month chemical packs for bromine, chlorine or Nature2 spas. These kits include a pre-filter for your water hose and up to a dozen other items.

What are Natural Spa Chemicals?

  1. Mineral sticks
  2. Ozone
  3. Enzymes


For those that want to avoid the smell of chlorine or the slightly softer scent of bromine on your skin, try approaching water sanitation from a different angle. Instead of using chlorine or bromine, you can use Spa Mineral Sticks, which use silver and/or copper ions to help purify the water. You can also use ozone, injected into the plumbing from an Ozonator. Both of these systems, coupled with regular use of MPS (a non-chlorine oxidizer), some extra filtering and careful attention to good water balance can allow you to operate most spas without the use of chlorine or bromine. Also in the natural chemical category are enzymes, which are natural scum eaters, helping to remove contaminants in the water by naturally digesting them. While not a 100% chlorine-free or bromine-free option, you can also reduce chemical use with a floating mineral system that uses supplemental bromine or chlorine cartridges.


If you made it all the way to the end of this post, you are now a well-informed hot tub owner who knows how to properly balance and sanitize spa water! The great thing about maintaining spa chemistry is that if things go really bad, you can always replace the water and start fresh. Then again, you should be doing this every three or four months, anyway. Remember to re-balance your water's chemistry, and rebuild the sanitizer levels or bromine bank after refilling.