Basic Hot Tub Water Chemistry


There are 4 main components to hot tub water chemistry that you need to be concerned about:

- Calcium Hardness

- Alkalinity Level

- pH Level

- Sanitizer Level


The calcium hardness is important because water that has high calcium will be cloudy and can cause scaling while water that has low calcium can damage the surfaces of your hot tub by “stealing” calcium from those surfaces. Calcium levels should be kept between 80 and 200 ppm. If your calcium levels are above 400, it is time to drain a refill your hot tub because there is no other way to reduce calcium hardness. To raise your hardness level if it is too low, simply add a calcium booster. You will only need to add calcium booster when you first fill your tub as calcium levels will not drop naturally.

The next component of water chemistry is total alkalinity. This is a measurement of the waters ability to neutralize acid but its primary purpose in your hot tub is to stabilize the pH level of the water. With improper alkalinity levels, your pH will have a tendency to bounce around so keeping the alkalinity level correct will prevent this and keep the pH stable. Ideal alkalinity levels are 80-120 ppm. To increase alkalinity, add a quality alkalinity booster to the water. If alkalinity is too high it can actually be reduced with pH reducer but it will typically come down over a period of time.


" pH is the most important aspect of hot tub water balancing... "


pH is the most important aspect of hot tub water balancing (sanitizer is not, strictly speaking, a balance component). Hot tub sanitizers such as chlorine and bromine work in a very specific pH range. Chlorine works best between 7.2 and 7.6 while bromine has a slightly wider range at 7.2 to 7.8. This is not to say that bromine is better because it is also slower acting than chlorine and requires slightly higher levels. The main takeaway here is to keep your pH in a range suitable for your sanitizer.

Finally, you’re sanitizer needs to be kept at appropriate levels for your hot tub depending on which sanitizer you use and whether you use water treatments or conditioners. With no other treatments, chlorine needs to be kept at between 2 and 4 ppm while bromine should be kept between 3 and 5 ppm. With a quality water conditioner such as Spa Marvel (which we HIGHLY recommend), you can reduce chlorine levels to 0.5 to 1 ppm which is one of the reasons we recommend it so highly.

Even after your water is balanced and has proper sanitizer levels, there is one other component to hot tub water chemistry that is critically important and that is shocking your hot tub. The process of shocking your tub simply means you add a compound which will cause the contaminants in your hot tub to be gassed off. You can get chlorine based shock which simply overwhelms the used chlorine in the water and gasses off the contaminants or, preferably, you can use a non-chlorine shock which uses a chemical compound to do the same thing without affecting your overall chlorine levels so you can get back in the tub sooner.

Ok so how do we balance the water properly? Here is your quick and easy guide:


  1. Check the water with a quality test strip and note your hardness level and your alkalinity level.
  2. Add calcium booster if needed to bring the hardness to between 100 and 200 ppm.
  3. Add alkalinity booster to bring your alkalinity level to between 80 and 120 ppm.
  4. Allow the water to circulate with the jets on low for at least 15 minutes.
  5. Test the water again to confirm alkalinity levels and check pH level.
  6. Add pH reducer (or increaser) to bring your pH level to between 7.2 and 7.6.
  7. Allow the water to circulate again for 15 minutes.
  8. Test the water to confirm proper alkalinity and pH levels.
  9. Add enough stabilized chlorine granules to bring the sanitizer to the appropriate level (depending on conditioners, etc.).
  10. Shock yout hot tub after each use with a quality non-chlorine shock.
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