The easiest way to raise the total alkalinity level in your hot tub or swim spa is to use an Alkalinity Increaser. You can also use baking soda to raise alkalinity. Use the chart below to determine the amount you need based on your current reading.
Increase your hot tub total alkalinity with alkalinity increaser. Low alkalinity affects your pH and can stain and damage your hot tub surfaces and equipment.
Yes. Baking soda can be used as an alkalinity increaser in pools and hot tubs. The main ingredient is Sodium Bicarbonate. But make sure the baking soda you use doesn’t have any additional additives. Use 1 tablespoon (17 grams) of baking soda per 100 gallons (379 liters) of water to raise alkalinity by 10 ppm (parts per million).
Now that you know how, let’s find out why you even need it.
You must balance your hot tub’s pH level (acidity) so that it feels good on your skin and allows your sanitizer or disinfectants (like chlorine or bromine) to be effective at killing bacteria.
If you have low pH (and alkalinity), it can cause corrosion of metal parts in your hot tub and skin irritation. On the other hand, if you have have high pH (and high alkalinity), it can cause cloudy water, calcium build-up, and skin irritation, too.
The pH (potential of hydrogen) is the primary measurement of how acidic or basic your water is. It’s on a scale from 0 to 14, with 7 being perfectly balanced. If the pH reading is closer to 0, that means your water is acidic (think battery acid). If it’s close to 14, it’s basic (think drain cleaner). The perfect pH is 7, which is what human tears are. Here’s our pH scale to help you understand.
In a hot tub, your pH reading should be more basic. The ideal range is between 7.4 and 7.6. But what about alkalinity?
Alkalinity is a pH buffer. I like to think of it as pH’s bodyguard. Without alkalinity in your water, it would cause wild pH fluctuations, and impossible to keep your pH stable. But why?
Everything affects the pH. When you soak in the water, the pH could go up or down. The same goes for if you add chemicals, turn on the jets, and leaving the cover off while it rains or snows.
We raise the alkalinity in a hot tub to protect the pH level from bouncing all over the place. The alkalinity takes the hit, so your pH remains stable.
You need to keep the total alkalinity reading in your hot tub between 100 and 150 ppm (parts per million). You can keep it as low as 80 ppm, but not any lower.
To test the spa water, you need either test strips or a liquid test kit. I prefer test strips because they’re quick and easy to use. Here’s the one I recommend.
Tests for 7 important chemistries in seconds: Total Hardness, Total Chlorine, Total Bromine, Free Chlorine, pH, Total Alkalinity, and Cyanuric Acid.
But they’re less accurate than a liquid test kit. So, if you’re a perfectionist, go with a liquid test kit with a digital reader.
NOTE: Before you can test your hot tub’s pH level and alkalinity, you need to know how many gallons of water it holds (or liters). If you need help, here’s our article on how to find out how many gallons your hot tub holds.
If you’re colorblind, you need to get someone else to read the strips for you. You’ll also need help with a liquid test kit. You can use a test strip reader app or a liquid test kit with a digital reader.
Whether you just filled your hot tub with fresh water or just enjoyed a long soak, the same process applies. And I’m assuming your alkalinity levels are low. Check out our guide on how to lower alkalinity in a hot tub here.
I recommend using chemical-resistant gloves and goggles when adding hot tub chemicals. Alkalinity Increaser and baking soda can irritate your eyes and skin.
Maintaining consistent alkalinity levels in your hot tub is crucial for water balance and the longevity of your spa. Here are some tips and best practices:
I sent an email to 15,000 hot tub owners and asked for any questions about balancing alkalinity and water pH. And I’ve got the answers!
Add an Alkalinity Increaser or Baking Soda (sodium bicarbonate) following the manufacturer’s instructions for the right amount.
No. When you raise the total alkalinity level with a Total Alkalinity Increaser or baking soda, it’ll also raise the pH slightly. If your pH is too high, I recommend checking out our guide on lowering hot tub pH.
It’s best to avoid using the hot tub if the alkalinity is too high. Going into a hot tub with low alkalinity can be uncomfortable and might cause skin and eye irritation. You can lower the total alkalinity reading by using pH Decreaser. Warning: do not use muriatic acid to lower alkalinity in a hot tub.
Adjust alkalinity first, as this can often help stabilize pH levels, making it easier to balance your hot tub’s water chemistry.
No. Shocking can actually raise the alkalinity (and pH) level of hot tub water if it contains chlorine. Non-chlorine shocks have less impact. We recommend shocking with non-chlorine shock for regular maintenance. Check out our complete guide on shocking a hot tub.
Baking soda can start raising alkalinity in a hot tub within a few minutes. Still, it’s best to retest the water after 15 minutes for accurate results.
The best way to lower alkalinity (and lower pH) is to use a
It will have no (or very little) effect on your total alkalinity reading. The main ingredient in pH increaser is sodium carbonate (which is very close to sodium bicarbonate). However, it’s not the chemical itself that won’t raise the alkalinity; it’s the amount. You only need a small amount of pH increaser to raise the pH. Check our article on raising hot tub pH for more information.
Matt is the founder of Swim University. He's been in the pool industry since 1993. His mission is to make pool care easy for everyone. Each year, he continues to help more people with water chemistry, cleaning, and troubleshooting.
Learn how to lower pH in a hot tub with pH Decreaser (Sodium Bisulfate). Here's how and the brand of pH Decreaser I prefer to use.
Looking for how to raise the pH in your hot tub? Or maybe how to lower the pH in your hot tub? Well, look no further. It's all right here.
Do you know which hot tub chemicals you need to keep the water balanced? What about when and how to add them? Get a hot tub chemistry education right here.
