The simple answer to knowing what chemicals to add and when can be found is simply by testing your water.
One of the biggest challenges for new hot tub owners is keeping their water clear, and that’s mostly related to keeping the water balanced.
Let’s look at what chemicals you need, how to add them, and some typical questions that new owners have.
What chemicals are needed for a hot tub?
Before you jump into what chemicals you need, let’s first look at what you need to maintain for healthy water and then look at what chemicals can do that. We also have some more information on what chemicals are needed to clean your hot tub.
The main parameters you need to maintain in a hot tub for balanced water are:
- pH – This is a measure of how acidic or basic your water is.
- Alkalinity – Total alkalinity is a measure of the buffering capacity of the water and this helps keep your pH from bouncing up and down.
- Sanitizer – Arguably the most important, sanitizer is responsible for keeping your water safe, clean, and sanitary. In the hot tub world, primary sanitizers could be chlorine, bromine or ozone and secondary sanitizers are mineral systems and/or enzymes.
- Calcium Hardness – Calcium hardness is a measure of hard or soft your water is and it consists of the amount of dissolved calcium and magnesium in your water.
- Cyanuric Acid (optional) – Cyanuric acid prevents UV rays from the sun from degrading chlorine. It’s only needed for tubs that are in direct sunlight.
Now let’s look at how each can be maintained.
| Parameter | Hot Tub Chemicals | How to add?* | Ideal range | Impact on hot tub |
|---|---|---|---|---|
| pH | pH Increaser pH Increaser or Soda Ash Decreaser Muriatic Acid or Dry Acid (sodium bisulfate) | Dissolve in a bucket of hot tub water and with the tub running pour slowly in front of a return jet. For liquid acid, dilute the recommended amount of acid by pouring it into a bucket of water, and with the tub running pour slowly in front of a return jet. For dry (powder) acid, mix with water and use the same instructions for liquid acid. * Acid is dangerous and should be handled carefully. Refer to the manufacturer’s safety instructions before use. | 7.2-7.8 | Low pH can cause pitting of surfaces, corrosion of your tub and its internal parts, and/or cracking. Dry/itchy skin and eye discomfort. High pH can cause scaling on the surface of your tub and clogged pipes or filters, |
| Alkalinity | Increaser pH Increaser or Baking Soda Decreaser Muriatic Acid or Dry Acid (sodium bisulfate) | Dissolve in a bucket of hot tub water and with the tub running pour slowly in front of a return jet. For liquid acid, dilute the recommended amount of acid by pouring it into a bucket of water, and with the tub running pour slowly in front of a return jet. For dry (powder) acid, mix with water and use the same instructions for liquid acid. * Acid is dangerous and should be handled carefully. Refer to the manufacturer’s safety instructions before use. | 80 – 120 ppm | Low alkalinity can cause pitting of surfaces, corrosion of your tub and its internal parts, and/or cracking. High alkalinity can result in high pH, calcium buildup, clogged pipes or filters, and/or cloudy water |
| Sanitizers | Bromine Chlorine Ozone Mineral/Ionizers UV | Bromine comes in tabular and granular forms. Tabs can be added to a floater or built-in brominator. Chlorine comes in tab form, liquid, and granular. Tabs can be added to a floater or built-in chlorinator, liquid can be poured slowly in front of a return jet with the tub running, and granular chlorine should be dissolved in a bucket of hot tub water before pouring in front of a jet. Ozone is injected by a built-in Ozonator, but you still need to maintain .5 ppm chlorine. Minerals and Ionizers come in various forms and devices such as floating ionizers or built-in ozonators. You still need to maintain ~.5 to 1 ppm chlorine or bromine. UV systems are typically built in and controlled by the hot tub control system. You still need to maintain ~.5 to 1 ppm chlorine or bromine. | 1-3 ppm 1-3 ppm NA NA NA | |
| Calcium Hardness | Increaser Calcium hardness increaser (Calcium Chloride) Decreaser The only way to decrease calcium hardness is by dilution, so you will need to drain some water and replace it with softer water. | Mix the increaser in a bucket of hot tub water and with the tub running pour slowly in front of a return jet. Determine the percentage decrease you need and dilute the water to lower CH (ex: CH 400 ppm, replace 50% of the water to lower to 200 ppm.) | 150 – 250 ppm | High calcium hardness can result in a sandy feel on the tub surface, scale buildup in plumbing, cloudy water, and/or a scaly ring around the water line. Low calcium hardness can make your water feel slimy, create excessive foaming, and/or damage internal tub components due to the corrosive environment. |
| Cyanuric Acid (Stabilizer or CYA) | Increaser Cyanuric acid comes in granular and liquid forms. It is also a chemical found in stabilized chlorine shock and tabs. Decreaser The only sure way to decrease CYA is by dilution, so you will need to drain some water and replace it with fresh water | Determine the percentage decrease you need and dilute the water to lower CYA (ex: CYA 100 ppm, replace 50% of the water to lower to 50 ppm.) | 30 – 50 ppm | IF CYA is too high then your chlorine will not be as effective and you will need to increase the amount of chlorine in the hot tub. If CYA is too low then you will need to add more chlorine because the UV rays will destroy your chlorine more quickly. |
*make sure the cover is off and the tub is running when adding chemicals
How soon can you use your hot tub after adding chemicals?
Another frequent question is how long to wait before you can use your hot tub. You should always read the manufacturer’s instructions, but a general rule of thumb is:
- Chlorine or bromine – 30 to 60 minutes
- Shock – wait until the chlorine level is within normal range again. If using non-chlorine shock then wait 60 minutes
- pH up/down & alkalinity up/down – 2 hours
- Calcium Hardness – 2 hours
- CYA – 1 hour
We prefer adding at night and letting the chemicals stabilize overnight before using the hot tub. Always test before using just to be sure that your water is safe.
Is it possible to maintain a hot tub without chemicals?
Contrary to some erroneous information on the internet, it is not possible to maintain your hot tub without chemicals. Some situations will require smaller amounts of certain chemicals, but left alone water will always become unbalanced in closed containers like pools and hot tubs. You can reduce your sanitizer demand with mineral and ozone systems, but you will still need a sanitizer.
Why does my hot tub smell like chemicals?
If your hot tub smells like chlorine, it is because it is unsanitary. Meaning, that it’s not clean or safe to swim in. What you are smelling is actually chloramine, which is “used up” chlorine. If you smell other chemicals then you should be sure to leave the cover off until it dissipates.
Can you use pool chemicals in a hot tub?
Some pool chemicals can be used, but it’s best to stick to chemicals made for hot tubs. Chemicals for hot tub care are more dilute and the directions are specific to smaller bodies of hot water. By the way, want to know what the ideal temperature is for a hot tub? Check out our blog for the ideal hot tub temperature.
What Do I Need to Do the First Time I Use the Hot Tub?
The first thing to do is to test the water to make sure your hot tub chemistry is balanced. After you use your tub you can also preemptively shock it to avoid any potential issues. You should always test your water frequently to keep your water looking as good as it did the first time you used it.
Do You Need to Add Shock after Filling a Hot Tub?
You do not need to shock as long as the water is clear and you get your sanitizer levels in range shortly after filling.
Where can I buy all the recommended chemicals for my hot tub?
You can purchase hot tub chemicals at your local pool and spa store, big box stores, or from online sellers.