how to decrease alkalinity in hot tub

Did you know one of the most serious problems for hot tubs and hot tub covers results from too much acidity or alkalinity? 

 Too much acidity or alkalinity can cause : 

  • Corrosion of the hot tub’s metal parts, including pumps and jets 
  • White or rust-colored scales on your hot tub’s plumbing 


When dissolved in water, chlorine forms an alkaline compound that raises the pH. Chlorine loses its effectiveness around pH 7.8, becoming an oxidation agent that corrodes the metal in your hot tub instead of killing bacteria. 

Is the Alkalinity in your hot tub high?

More specifically, alkalinity is the capacity of water to resist acidification. To put it simply, alkalinity acts as pH’s bodyguard, which is the measure of the acidity or base of your hot tub water. Without alkalinity, the pH would be quite out of balance. 

The goal? Keep the pH balanced between 7.4 and 7.6. If the pH reading is higher, the alkalinity of your hot tub is probably too high. By balancing a high pH, you will decrease the alkalinity of your hot tub.

What are the causes of a high alkalinity in a hot tub? 

  • Too many chemicals
  • Sweat, lotions, perfumes and other bodily fluids
  • Water source (quality)
  • Human error

What happens when the alkalinity in your hot tub is too high? 

When the alkalinity is too high in a hot tub, it can make your sanitizer (chlorine, bromine, etc.) useless. Bacteria can also grow in the water and cause problems in addition to causing skin problems. In addition, it can cause scale problems in your hot tub.

How to lower the alkalinity of your hot tub?

In order to lower the alkalinity of your hot tub, we recommend that you add a pH decreaser. Even though alkalinity and pH are two different things, this solution often works to resolve the issue.

Our pH Down Solution will allow you to lower the pH level in your hot tub water.

Here are the steps to follow :

  1. Test the water to find out the the current alkalinity reading to see if you need to lower it some more
  2. Add the pH decreaser or use a non-chlorine based sanitizer
  3. Test your water again after 24 h and readjust if needed


If you are using municipal water and our pH decreaser, the hot tub pH will likely remain in the normal range of 7.2-7.8.

It is still a good idea to test the alkalinity on occasion, to ensure your municipality’s water treatment facilities are maintaining the quality of the water.

Testing your pH is essential. Dissolved solids in well water can lead to a huge range of pH values, from very acidic to very alkaline. 

Should you adjust alkalinity or pH first?

Increasing alkalinity will also increase pH. If both readings are low, start by increasing the alkalinity first with our alkalinity booster. Then test the water again. If the pH is still low, but the alkalinity is good, just add a pH accelerator.

Should I correct the pH with white vinegar or baking soda? 

This is generally not a good idea.

Vinegar and baking soda can interact with other dissolved solids and cause scaling. It can also lead to bad odours coming from your hot tub.

Avoid headaches by investing in hot tub pH balance adjusters : odourless, colorless, concentrated acidic and alkaline solutions designed to alter pH without interacting with any dissolved solids or chemicals. The Cover Guy has everything you need for your hot tub!

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