How To Reduce Alkalinity In A Hot Tub In 3 Simple Steps

How To Reduce Alkalinity In A Hot Tub

To reduce alkalinity in a hot tub when the level is high is a vital part of hot tub maintenance. Have you been puzzled why the effectiveness of your hot tub water sanitizer is gradually becoming lesser and lesser, why your hot tub filters are beginning to clog so much, and your hot tub suddenly looking cloudy? If you have, then the culprit you should hold responsible for this is Alkalinity. Alkalinity is simply a measure of the ability of a water body to maintain an almost stable pH level, by neutralizing acids and bases.

High level of alkalinity in a hot tub can be reduced by adding sodium bisulfate to the water in the hot tub. Alkalinity is not a chemical that has contaminated the water in your hot tub, if that is what you might be wondering. It is rather a measure of the resistance strength of your hot tub water against the chemicals that seek to alter the nature of water. A good thing, yes, but only when it is in moderate levels as high or low alkalinity is not a good thing for your hot tub or you.

The best way to reduce the alkalinity of water is by reducing the pH since a high Total Alkalinity (TA) means the pH level is high. So applying pH decreaser (sodium bisulfate) to water, will lower the pH level and in turn the total alkalinity.

But first, how do you know when the alkalinity of your hot tub is high or when to stop trying to reduce it and increase it instead?

What is the ideal Total Alkalinity level?

Water in its pure state has a pH value of 7. This is considered to be neutral, meaning not acidic nor alkaline (basic). Below this level, it gradually becomes harmful to humans. But above this level, it becomes alkaline and is only but discomforting to the body as it increases and not harmful to humans; except to those who have kidney disease.

So it is a good practice to have relatively alkaline water to help sanitize your hot tub and curb chances of extreme acidity. The ideal hot tub total alkalinity is within 80 – 120 ppm (parts per million) or a pH level of 7.4 – 7.6. This level is moderate enough to make your stay in the hot tub comfortable enough as there will be no itching and chances of corrosion of hot tub pipes reduced.

What causes high alkalinity in a hot tub?

Excessive chemicals: Frequently adding pH reducers to reduce the pH of water in your hot tub will eventually contribute to high total alkalinity. Also, chemicals from creams and other skin products we use can contribute to high total alkalinity.

Sweat: Especially on very hot days when the body tends to be sweatier. Body oil and sweat seep into the hot tub water and amount to an increase in total alkalinity. Your hot tub might become cloudy after a party due to high amounts of sweat and body oil dissolving in the water.

Water source: If your source of water supply is water from a water company, then this might be another reason why the total alkalinity of your hot tub is high. To prevent their supply pipes from getting corroded, water companies often use water with higher alkalinity to address the problem. While this might be a perfect solution to their problem, it is one of the causes of your hot tub problems. You have been adding water messing with your hot tub TA and pH levels without knowing.

Water companies are required by the law of the U.S. Environmental Protection Agency (EPA) to provide Consumer Confidence Reports (CCRs), also known as water quality reports to their customers. This report contains information about the content and quality of your drinking water. So you can put a call through to your water supplier and know if your water source is the course of your hot tub headaches.

Effects of high alkalinity

Aside from reducing the effectiveness of the sanitizer, high alkalinity levels can be the beginning of a chain of problems. From creating discomfort for the hot tub user to creating a nice breeding ground for some unwanted things and adversely affecting the overall functionality of the hot tub system. Maintaining an ideal alkalinity level is important if you do not want to pile up additional maintenance costs.

The following are the effects of very high alkalinity levels on the hot tubs.

  • An alkalinity level that is too high leads to an imbalanced pH level, which contributes to high calcium levels.
  • Itchy skin and irritation in the eyes. The high calcium level induces water scaling and tends to make the skin itchy since the water is cloudy with floating particles. As water enters the eyes, irritation all occurs.
  • The high alkaline level in the hot tub neutralizes every little attempt to increase the pH level. And thus there is a pH lock which can be a problem when the pH level is very low.
  • Water scaling on hot tub surfaces and equipment. Hot tub water with high alkalinity makes it possible for particles to easily solidify and come out of the solution causing the substance to keep afloat in the water. Most of the other issues that come up as a result of high total alkalinity in hot tubs are linked to water scaling.
  • Clogged pipes and filters due to particles coming out of the solution. The free-floating particles in water gradually accumulate in the pipes and filters and clog them up.
  • Reduced water circulation. Since the pipes and filters are now clogged, water flow in and out of the hot tub gradually gets reduced. The more clogged up the pipes and filters, the lesser the water circulation.
  • Higher water pressure in the piping system. Regardless of the pipes being clogged, the pump still pushes water through. This causes pressure to gradually build up in the pipes and can lead to cracks in them.

How do I lower the alkalinity in my hot tub?

If you find your hot tub has alkalinity above the ideal range of 80 – 120 ppm, then it is time for you to consider lowering it if you still want to enjoy the relaxing hot tub experience. Learning how to reduce alkalinity in hot tub is very important for every hot tub owner.

Earlier, I mentioned that the easiest way to lower alkalinity is to add sodium bisulfate (commonly known and pH reducer) to the water. But then, you cannot just pick it up and pour it into your hot tub. You can be doing more harm than good to the TA of your hot tub if it is not in the right proportion. An excess might end up making your hot tub water acidic, and very little might not do the trick if the TA was very high in the first instance.

Step 1: The first step is knowing how much water your hot tub holds. Then we can estimate the quantity of sodium bisulfate we need to add per unit of water to get the desired TA level.

Step 2: Next, is to test the current TA reading of your hot tub to know how far it is from the ideal TA levels, and if there is any need to reduce it in the first place. This can be done using a liquid test kit or hot tub test strips.

For a hot tub that holds 1,000 gallons of water, lowering the total alkalinity by 10 ppm requires about 3 ounces (85 grams) of sodium bisulfate. Knowing this will help you do the math as regards the capacity and TA of your hot tub. For example, a hot tub that holds half of the water capacity of the above will require about half the quantity of sodium bisulfate to lower the TA by the same amount.

That is to say, a hot tub holding 500 gallons of water will require about 1.5 ounces of sodium bisulfate to reduce the total alkalinity by 10ppm. A smaller two-person capacity hot tub will require lesser to achieve the same result.

Step 3: Now that you know the right quantity to use for your hot tub, turn on the hot tub and sprinkle the powder on the surface of the water. With hot tub running, it is going to mix easily. Turn off after about 20 minutes and allow to rest for an hour or more. Test, and add more following the step until the desired level of total alkalinity is achieved.

Sodium bisulfate takes time to make the required changes. So it is best to wait for about 24 hours before testing the water finally to see if the desired level has been achieved.

Can you go in a hot tub with high alkalinity?

Unless you have some kidney disease, going into a hot tub with high alkalinity is not exactly harmful to humans as a hot tub with a low pH level. Now, you might be wondering if there is any need in reducing the total alkalinity of your hot tub since it is not harmful. While it might not be harmful, it can cause great discomfort from itchy skin to irritation in the eyes. So it’s not safe to use a hot tub with high alkalinity level.

Will alkalinity decrease on its own?

Alkalinity with time reduces on its own. This is because, of the natural process and induced chemical reaction caused by the aeration of water in the hot tub. But this process is painfully slow compared to the rate at which alkalinity will increase due to frequent usage of the hot tub.

Does baking soda lower alkalinity?

Baking soda does not lower the alkalinity of water. For water to have lower alkalinity, it means the ability of the water to break down acids is reduced. Baking soda has a very high alkaline pH level and will only add to the present alkalinity of water in your hot tub rather than reduce it.

Hot tub test strips

These are strips used for checking the total alkalinity or the pH level of hot tub water. They are a must-have when it comes to keeping tabs on the condition of your hot tub. Using the testing strip is quite easy and you can get results in the following steps.

  • Ensure even conditions. First, by starting and circulating the water in the hot tub for some 2-5 minutes before getting a sample of it in a bucket.
  • Carefully holding the testing strip at the grip side, dip it into the water sample in the bucket. Allow for about 15-20 seconds before removing. Shake off the water remaining on the stripe.
  • Check the color of the strip and compare it to the color chart on the testing strip bottle. From the color, you can be able to tell if your hot tub is too acidic or alkaline.

How to lower alkalinity without lowering pH

Reducing total alkalinity level goes hand in hand with reducing the pH level of water in a hot tub. Maybe because the same chemicals are used, but separating both processes is best said to be impossible. The only way possible is to lower the alkalinity first and then seek to increase the pH level afterward. Over time, pH levels do increase naturally, we just have to speed up the process. This is done by aeration of the water in the hot tub. This is useful as in some cases when acids are added to reduce alkalinity all at once, the pH level becomes too low and thus harmful.

Aeration causes CO2 gas dissolved in the hot tub water to change back to gas and come out of the water. This triggers some chemical reactions to occur within the bid to achieve a normal composition condition. In the process, hydrogen ion (H+) is consumed and gradually becomes lesser. Since pH is the measure of hydrogen ion concentration, less of it means the pH level gradually goes up while total alkalinity remains unchanged.


Keeping an ideal total alkalinity level is very vital to the general comfort of your hot tub. Always check for and lower the alkalinity level whenever it climbs up or climbs down the ideal level. It will save you some stress of running maintenance now and then due to some faulty parts, prevent algae from growing in your tub as cleaning would be effective and easier, and eliminate risk and discomforts associated with extreme TA levels.

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