One of the most daunting parts of owning your own spa is understanding all the chemicals involved.
This is why ready-made hot tub chemical starter kits are a tempting purchase for new spa owners. They seem like the perfect solution—everything you need in one box.
But, these kits often include unnecessary extras which can lead to wastage and higher costs. For most people, it's actually better to buy individual chemicals separately so that you get only what you need.
In this article I'll show you exactly what chemicals to buy for your new hot tub (and exactly how to add chemicals to your hot tub for the first time) so that you don't end up wasting money on unnecessary products which you may never use.
Just want to know what you should buy? Jump to the product list.
What is a hot tub chemical starter kit and why do I need one?
Whenever you fill your hot tub with fresh water, you need to add a variety of chemicals to 'balance' your water. This is so it's both safe to bathe in, and also safe for your spa's equipment. Poorly balanced water can lead to damage, scale, and even corrosion.
Hot tub chemical starter kits are packaged bundles of the various chemicals you need for maintaining your hot tub at home. Some of these chemicals include pH adjusters, sanitizers, metal reducers, and water hardeners.
A hot tub chemical starter kit can be useful to have on hand if you do not know what chemicals you need or how much to purchase for hot tub startup and ongoing maintenance.
Why are ready-made kits not as good value as they seem?
There are a couple of reasons I don't recommend new spa owners buy one of these kits:
- You use up the products at very different rates. I went through some of the products very quickly, and still haven't finished others to this day (several years later). It's hard to make a one-size-fits-all kit because the water you're starting with is the main factor which influences how much of each chemical you're going to need. This will obviously depend on the water source where you live.
- There are common household alternatives to some spa chemicals which are usually much cheaper than the branded versions. For example, baking soda can be used to raise total alkalinity in your spa. I'll be sure to include these in this article whenever there's a chance to save some money. Kit manufacturers are of course not going to tell you this because they make more money if you buy their branded products (even when they're selling you the exact same chemical).
Which chemicals should you buy for your new spa?
This depends on which kind of sanitizer you want to use, but also on things like if you live in an area with hard or soft water. Most of the products will apply to everyone though—I'll point out when there's anything unusual you might need to consider.
Here's the list. It's 8 or 9 products, depending on which sanitizer you choose. Below the list I have included a full explanation of each item, plus some tips on things like how to choose your sanitizer if you're still not sure.
|Product||What it's for|
|Sanitizer: Chlorine or Bromine||Kills bacteria and keeps spa water clean and safe to bathe in.|
|Floating Tablet Dispenser||In bromine spas, you add tablets in one of these which release small amounts of bromide over time.|
|Shock||Works with your sanitizer to remove contaminants from the water.|
|pH Increaser & Decreaser||pH is how acidic or alkaline your water is, and it's important to maintain the right level.|
|Total Alkalinity Increaser||Total alkalinity (TA) helps to keep your pH stable.|
|Calcium Hardness Increaser||Calcium hardness determines how 'hard' or 'soft' your water is.|
|Test Strips||The easiest way to read your sanitizer, pH, and TA levels.|
|Metal Reducer||Helps neutralize the metals and other trace minerals in your water.|
Sanitizer is arguably the most important chemical in a spa because it's what keeps your water free from bacteria and safe to bathe in.
The two main options here are bromine and chlorine. There's a lot of debate about which is better, but if you're still undecided, here's a brief summary of the differences:
|Chlorine is a more effective sanitizer which means it's faster to kill contaminants than bromine||Bromine is gentler on the skin, whereas chlorine is more drying and can be irritating to some people, causing redness, itchiness or rashes|
|Chlorine is cheaper on average||Bromine has a lower pH, which can make your water balance easier to maintain|
|Bromine is more stable, which means the levels stay more consistent, so it lasts longer and doesn't need topping up as often as chlorine|
Floating Tablet Dispenser
This one is probably only relevant if you opt for bromine. In a bromine spa, you first build up a 'bromide bank', and then add brominating tablets in a floater which release small amounts of the chemical over time.
If you choose chlorine, you're better off using granules. Although you can get chlorine tablets, these are mainly designed for pools and can be damaging to spas if used incorrectly.
Why shouldn't you use chlorine tablets in a hot tub?
Chlorine tabs contain Trichlor which is acidic. This means your pH and alkalinity will reduce when using these tablets, so you'll need to adjust the chemicals in your spa more often to keep it balanced.
You also risk bleaching an obvious ring around the shell, especially if you have an acrylic spa. Granules don't have this issue because they're closer to neutral than Trichlor tabs.
There is one exception: you can use chlorine tabs if you have an inflatable or other kind of non-acrylic spa.
The Spa Choice bromine kit I bought came with a floater or 'brominator', but it was one of the things I didn't like about it. Let me explain why.
There are a few different designs of brominator. These are the most common shapes you'll find:
The type on the left is the one that came with the kit, but is also a less sophisticated design. The top has an opening and the bromine tablets are placed inside. You twist the bottom to try to limit how much water can get inside, but it's not the most accurate mechanism.
The one on the right is my preferred type. The tablets stack up inside the tube, and you partially unscrew the bottom to expose the lowest tablet(s). The water cannot reach the tablets above. This design gives you fine-grained control over exactly how much tablet is exposed to the water at once, so not all the tablets will start to dissolve right away.
Spa shock is a chemical treatment that is used (along with your sanitizer) to remove contaminants such as oils, lotions and sweat from the water.
You should add a dose of spa shock about once a week, or after you use the spa—whichever is more frequent.
Here's how shock works: over time, your sanitizer binds with contaminants in the spa, which gradually reduces its effectiveness (if you get cloudy water, this is probably what's going on). What happens when you add shock is that it kills these contaminants, freeing up your sanitizer so it can start working again.
There are two different types of shock: chlorine and non-chlorine. You can actually use either regardless of the main sanitizer in your spa. This means that even if you have a bromine system, you can still use chlorine shock.
pH Increaser & Decreaser
pH is a measure of how acidic or alkaline a solution is. It's an important part of spa chemistry because If your pH falls out of its ideal range (more on that in a second), your water could become unsafe.
If pH is too high, it can lead to scale buildup and cloudy water. If pH is too low, you'll have acidic water that can corrode surfaces and equipment—which could become an expensive problem! Both can cause itchy or dry skin and burning eyes.
Spa pH: the ideal range & how to maintain it
The pH scale goes from 0 to 14, with 0 being the most acidic and 14 being the most alkaline (or basic). Pure water is neutral at a pH of around seven. The ideal range for pH in a hot tub is slightly alkaline at 7.2-7.8.
After sanitizer, pH is one of the most important things to test in your water chemistry. All hot tub test strips will give you a visual pH reading. If you want a more accurate way to test your spa's pH level, you can invest in a liquid test kit.
To maintain perfect pH levels in a hot tub, you'll need both an acid (increaser) and alkali (decreaser) on hand depending on which way your spa is out of range. That said, although my starter kit came with equal amounts of pH increaser and decreaser, I've actually not had to use any increaser at all!
Raising total alkalinity (I'll cover that in the next section) also causes pH to rise, and that's been enough for me to keep the pH up too. I actually have more of the opposite problem: I need to add acid to bring the pH down fairly regularly because it tends to drift too high.
Total Alkalinity Increaser
Although alkalinity and pH are closely related, they're not the same, and it's important to understand the difference.
Total alkalinity (TA) makes it easier for your water to resist pH changes (it's commonly known as a pH buffer). Unlike pH, it's measured in ppm, which stands for parts per million. That's because it's actually a measurement of all the dissolved alkaline substances in the water.
If all this sounds confusing, remember that you don't need to memorize too much of the theory. It's just useful to have some basic knowledge of how all these measurements affect each other.
Low TA: what happens & how to prevent it
If your total alkalinity is too low, it can cause pH levels in the hot tub to fluctuate too much. To maintain an adequate TA level, you need to add more dissolvable alkaline substances to the water when the TA drops.
Remember I mentioned household chemicals? Here's one case where that applies. When you need to raise TA, a cheap and easily available alkaline product is sodium bicarbonate, which is just baking soda. This is literally the same chemical you'll find sold as TA Increaser, except it's much more expensive when sold as a branded spa product.
It's much more common for TA to be too low than too high, but if you do find yourself needing to lower it, you can use the same chemicals you would use to decrease pH (usually dry acid or muriatic acid).
Calcium Hardness Increaser
Calcium hardness is the amount of dissolved calcium and magnesium in your spa, which determines how 'hard' or 'soft' your water is. You need to maintain the right level of calcium hardness if you don't want your water to either be corrosive or scale.
Exactly how much of this you need will depend on your source water. I live in an area with extremely soft water, so I bought a HUGE tub of calcium chloride after setting my hot tub up for the first time (I used almost all the stuff that came in the starter kit the very first time I filled the spa!).
You can usually find the hardness of your local water supply online to get a rough idea of how much calcium you are likely to need. You can also buy a test kit just for hardness, or have your water tested at a pool supply store to find out the hardness of your exact water, which is probably more reliable than just guessing based on where you live.
Hardness is pretty much a one-time setup thing; it doesn't really change between refills unless you add or remove water.
Test strips are used to test the water for bromine or chlorine levels as well as pH and TA. They are quick and easy to use, but can be inaccurate. They're totally fine for beginners or your weekly checks, but if you're serious about your spa's water chemistry, you'll eventually want to consider a more advanced test kit.
This is another big downfall of the pre-assembled kits: they often don't include test strips, so you may have to buy these separately anyway. Mine didn't include test strips when I bought it, but it looks like they have added them to the more recent version of the kit at the time of writing.
You can get test strips for chlorine-based spas that are different from those needed for bromine-based systems, but these JNW Direct ones will read both.
Test strips usually take about 2 seconds and give a visual reading on the strip itself—just dip it in the water and wait to see the a color change! Then compare it against the chart on the outside of the bottle.
Another product that came in my starter kit was a metal reducer (it's also sold as 'metal free').
This chemical helps prevent the buildup of scale and calcium on surfaces by neutralizing the metals and other trace minerals in your water. This is especially good to use if you've got hard water, as it can help prevent any nasty calcium deposits around your jet nozzles.
It's only necessary to add metal reducer once after filling your spa with fresh water, or if you top up the spa partially at any point. Otherwise it's more of a preventative measure, rather than something to fix an issue.
Useful things to buy for ongoing spa maintenance
That covers everything you need for first-time spa setup. But there are a few more nice-to-haves which will make your life easier as you find yourself doing regular spa maintenance until the next refill.
Jet & Line Flush
Before you start the next drain-and-refill process, you'll want to use a jet and pipe cleaner. Ahh-Some Hot Tub/Jetted Bath Plumbing & Jet Cleaner is my current favorite. It's the only way to dislodge and kill any mold or biofilm growing inside the plumbing lines.
I wrote a detailed guide on how to use it and really get your spa clean (inside and out) before you fill it up again.
You need to rinse your filters with a hose and optional cleaning spray every 2-4 weeks, and then give them a deep clean when you change your spa water (or more frequently if your spa has heavy usage).
You can see the full process in this article which also features before and after photos using my favorite filter cleaner.
When your spa is all fresh and clean and filled for the first time, you won't be thinking of a skimmer, but trust me, you'll be wanting one soon enough.
Skimmers are those handheld nets that collect floating debris from your spa water so it can't clog up your filter and cause problems in the future, like this one from Amazon:
They're not expensive, but will be so worth it next time you spot a leaf, insect or piece of grit floating around in your spa.
How to balance the water after filling up your hot tub
So, you've filled your spa with fresh water and purchased all the necessary chemicals. How do you know what to add or test first?
Here's the basic process:
- Let your hot tub heat up to a temperature of 100°F (don’t skip this step—chemicals may not work properly if added to cooler water)
- Add metal free to remove metals from the water which can stain equipment. Circulate for 30 minutes.
- Add calcium chloride to raise your water’s calcium hardness to 150-250 ppm. You can check your local municipal water supply to find out what the natural hardness of the water is in your area to get an idea of how much you'll need to add. Circulate for 20 minutes.
- Add sodium bicarbonate to raise the water’s total alkalinity (TA) until it’s within the range of 100-120 ppm. Circulate for 30 minutes.
- Test the pH, and then add either pH up (alkaline) or pH down (acid) until it’s within the range of 7.2-7.8. Circulate for 30 minutes.
- Add your sanitizer up to the appropriate levels. You’re aiming for 1-4 ppm for chlorine, and 2-6 ppm for bromine.
- Shock your spa, and then wait for the sanitizer reading to drop to a safe level. Once it measures in the above ranges, your spa is ready to use!
How do you know what quantities of spa chemicals to add?
Figuring out the right dose of each chemical is usually a calculation based on how many gallons of water are in your spa. So, you need to know the volume of your spa in gallons to be able to determine how much of each chemical you need.
Write down the volume of your spa in gallons, and then make a note of the dose of each chemical that you add (that way, you'll have the amounts for reference and won't have to do the math again next time). For example, if a particular chemical says to add 4oz per 400 gallons, and you have a 200-gallon spa, make a note of 2oz as you now know that's going to be your dosage.
You'll also get to learn the needs of your spa over time, like if pH tends to rise or fall, or if you struggle to keep TA high enough etc. These things usually follow the same patterns and don't just happen randomly.
In any case, always follow the instructions on the pack carefully (at least at first) to make sure you're using safe amounts for you and your spa.