How To Lower Alkalinity In Hot Tub?

How To Lower Alkalinity In Hot Tub[2 Effective Solutions]

Alkalinity in hot tubs is calculated using pH values. You must lower the pH levels in order to reduce hot tub alkalinity. You can do this in a few different ways, including by adding muriatic acid right to the water.

You can either accomplish this gradually over time on your own, or you can add a chemical reducer that slowly lowers the pH levels over time. In this article, you are going to learn about how to lower alkalinity in hot tubs.

What is Alkalinity?

Alkalinity acts as a buffer for the pH of your hot tub water, preventing extreme pH swings. To maintain stable pH levels, it is crucial to balance your total alkalinity.

You should have a total alkalinity of 100 to 150 parts per million (ppm). The pH of your hot tub should be 7.4 to 7.6. Anything significantly higher or lower can mess with the chemistry of your hot tub’s water, reduce its capacity for sanitization, and eventually harm your tub’s equipment.

How To Lower Alkalinity In Hot Tub?

You can read: Remove Iron from Hot Tub Water: The Ultimate Guide

How To Lower Alkalinity In a Hot Tub

Whatever the cause, you must reduce the high alkalinity of the water in your hot tub if you want to prevent any unwanted effects. However, you also don’t want to drop it too much because that could cause the pH levels in your tub to become out of control.

Here, I’ll talk about utilizing muriatic acid, one of the most popular methods, to bring the alkalinity of your tub down to the proper levels.

There are two methods for reducing total alkalinity: Muriatic acid and Sodium bisulfate, a pH reducer. Whatever approach you choose, keep in mind that it will also cause your pH levels to decrease. Follow the guide below to use both methods correctly.

Muriatic Acid

  • Turn off pumps: This will stop the water in your hot tub from moving, which is important for the following procedures. If you want to allow the water enough time to settle, you should give it at least an hour after you switch off your pump.

Aeration of the water brought on by movement can increase the alkalinity of the water in your tub. The ideal conditions for decreasing alkalinity are created by allowing it to come to a complete stop.

  • Read the user manual: The recommended amounts to add to your hot tub water may vary depending on the particular tub product. Carefully read the labels and follow all instructions and dosages appropriate to the size of your tub. You might need to compare the suggested dosages to the alkalinity of your tub’s water right now.
Mix the Muriatic Acid
Mix the Muriatic Acid
  • Pour the solution: Muriatic acid should be added to the deepest part of your hot tub. Give it about an hour to sit in the quiet water. As a result, the tub’s overall alkalinity will decrease and the muriatic acid will have a chance to aerate spontaneously.
Pour the solution slowly
Pour the solution slowly
  • Turn on pumps: You ought to switch your tub’s pump back on after that period of time for natural aeration. Allow the muriatic acid to settle for a few hours so that it can flow throughout the entire tub.
  • Test the alkalinity: It will be time to check your water levels once more after a few hours. Check the pH and alkalinity levels using an alkalinity test kit to see how much each has decreased. You might need to repeat the procedure if further lowering is necessary.
Retest using test strips
Retest using test strips

Sodium Bisulfate

Acid salt or dry acid, commonly known as sodium bisulfate, is offered for sale as a pH reducer, pH minus, or pH decrease. Although it is safer to use, it functions in the same way as muriatic acid. Even though this approach is safer, it is also more expensive. And you’ll still need to keep the dry acid stored in a dry, moisture-free area.

Keeping in mind that both your alkalinity and pH will decrease as a result, be sure to retest both after.

  • Calculate the appropriate amount to add to your hot tub’s water by using the instructions on the product.
  • Sodium bisulfate should be mixed with water until the bucket is 3/4 full.
  • Mix the mixture with a wooden stick until all the grains dissolve entirely. Undissolved grains could drop to the tub’s bottom and ruin the top.
  • Starting at the deep end, slowly pour the dissolved solution around the entire tub’s circumference.
  • Your water’s pH and alkalinity should be retested. Repeat the process if necessary.

Amount Of Sodium Bisulfate needed to lower the alkalinity

Spa Gallons25 ppm50 ppm75 ppm100 ppm120 ppm
100 gallons0.5 tbs for 5 days0.5 tbs for 9 days0.5 tbs for 13 days0.5 tbs for 15 days0.5 tbs for 17 days
200 gallons1 tbs for 5 days1 tbs for 9 days1 tbs for 13 days1 tbs for 15 days1 tbs for 17 days
250 gallons2 tbs for 4 days2 tbs for 8 days2 tbs for 11 days2 tbs for 13 days2 tbs for 15 days
300 gallons2 tbs for 5 days2 tbs for 9 days2 tbs for 12 days2 tbs for 14 days2 tbs for 18 days
400 gallons2.5 tbs for 5 days2.5 tbs for 9 days2.5 tbs for 13 days2.5 tbs for 15 days2.5 tbs for 17 days
500 gallons3 tbs for 5 days3 tbs for 9 days3 tbs for 13 days3 tbs for 15 days3 tbs for 17 days

What Causes High Alkalinity

The water in your hot tub should be somewhat alkaline, but too much alkalinity can be just as harmful as too much acidity. To reach this higher level of stability, many individuals use things like baking soda to increase the alkalinity of their tub.

Others don’t need to put in as much effort because their water source is already naturally alkaline. Both of these scenarios might lead to water that has an excessively high alkalinity level because these factors vary depending on the individual.

What Happens When Alkalinity Is High?

A high level of hot tub alkalinity can make the water appear murky. In a process known as “calcium scaling,” the water will also begin spilling the substances it absorbed onto the surfaces of your tub.

Any tub will look unpleasant due to scaling and hazy water, but there are other negative impacts as well. Filters can become clogged due to high alkalinity, which can be difficult and expensive to fix.


Can baking soda reduce a hot tub’s alkalinity?

No, using baking soda won’t make you less alkaline. Both the alkalinity and pH of your hot tub water will increase if you add sodium bicarbonate or baking soda. Hot tub owners should always keep baking soda on hand to use in place of an alkalinity increaser.

How can alkalinity be reduced without reducing pH?

Since total alkalinity and pH are inversely correlated, it can be exceedingly difficult to reduce total alkalinity without lowering pH. As a result, adding acid to the tub will lower the overall alkalinity while also lowering pH. You can aerate your tub’s water if you need to boost the pH after applying acid. By doing this, the pH will rise once more without harming the alkalinity. If you need to drop the alkalinity more after the initial testing, try to be patient during the entire procedure.


Hi, I'm Shimul, the founder of Pooltub Life. I'm excited about sharing the latest outdoor living trends with you. My goal is to provide you with up-to-date information that will help make your POOL & HOT TUB stylish and enjoyable. Read About Me More । Follow on Facebook

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