What Causes High Alkalinity In Hot Tubs?

What Causes High Alkalinity In Hot Tubs?

High or low alkalinity – which is best? This is one of the frequently asked questions by new hot tub owners who are trying to keep their water at the healthiest level possible. Hot tub water’s pH is vulnerable as even the smallest alteration will significantly interfere with the pH.

Keeping the required alkaline level, however, takes care of the alterations in pH before any significantly pH interference. High alkalinity is not a bigger issue compared to low alkalinity. However, we will dwell more on it.

The reason why high alkalinity does not seem to be a big problem is that most hot tub owners sanitize and get rid of the water in their tubs every 3 to 4 months. This keeps particle accumulation at bay.

Having known that, some of the proven causes of high alkalinity in hot tubs are:

  • Chemicals: Deliberate or indeliberate addition of chemicals in large quantities has the ability to increase the alkalinity without you noticing. However, to avoid it, ensure that your tub is cleaned at least every 3 months.
  • Personal Mistake: Attempting to increase the alkaline level of your water (in case of low alkalinity) might actually lead to you increasing the alkaline level beyond the required measure. To avoid this, seek after the services of professionals.
  • Skin Care Products: Sometimes, the problem does not come from using excessive amounts of chemicals. The issue might as well arise from your daily skincare products. You should know that some of your daily skincare products (e.g., creams, sprays, and other body ointments) are capable of increasing the pH of your tub’s water. If your body gets into your tub, especially with stuff like sweat, your tub’s alkalinity is bound to go up the scale. To keep this in check, ensure that you shower before you get immersed.
  • Local Water Supply: Your residential area might have a water source that has a high alkalinity reading. This, too, can cause an increase in your tub water’s alkalinity. In cases of uncertainty of the alkalinity level of your area’s water, request a water report/ reading from your local authority.

Read further to learn more about alkalinity – meaning of alkalinity, its importance, high or low alkalinity, and balancing it in your hot tubs.

Meaning of alkalinity

Also referred to as total alkalinity, it is the measure of the extent to which your tub’s water can counteract the effect of acids. Alkalinity is an important aspect of keeping the pH levels balanced because it helps in resisting extreme changes in pH.

In this context, it does not mean how basic or less acidic your water is. Instead, it means the measure of the quantity of alkaloids in your tub’s water.

Alkalinity gives an accurate account of the quantity of alkaloids such as hydroxides, bicarbonates, carbonates, etc. present in your water. Unlike the normal pH measurements, it is accounted for in parts per million (ppm) and for your knowledge, your alkalinity level should fall in the range of 80 – 120 ppm.

What’s its importance?

Naturally, balance is a necessity. It is in that vein that your water’s alkalinity must be kept balanced at all times. Keeping an unbalanced alkaline level in your water can lead to serious aftermaths ranging from a noticeable water color change (colorless to green) to skin problems – and even equipment defects.

High or low alkalinity?

Low Alkalinity

To start with, low alkalinity is not noticeable but is more disastrous, compared to high alkalinity. As in the case of low pH (which can be really dangerous for your hot tub), keeping a low alkaline level has damaging effects some of which include:

  • Water pH fluctuation
  • Increase in acidity of hot tub’s water leading to skin irritation, skin dryness, itchy eyes, etc.
  • Delamination of hot tub surfaces
  • Ineffectiveness of hot tub sanitizers e.g., chlorine
  • Corrosion of metallic parts of the hot tub e.g., pump seals, pipes, etc.
  • Stain on hot tub surfaces

Although low alkalinity has drastic effects as mentioned above, there are working remedies for raising it to a reasonable level. One of the two known ways is the addition of sodium bicarbonate (as in baking soda).

This method will help in increasing the pH of your tub’s water, thereby increasing the alkalinity from low to normal. You can also try out any type of alkaline-level raising product.

Just ensure that after the addition of either sodium bicarbonate or any alkaline-level raiser, allow the water to sit for over 7 hours before checking again.

High Alkalinity

High alkalinity does not pose a whole lot of threats compared to low alkalinity. But still, it has to be addressed to ensure smooth, comfortable usage of your spa, as well as the longevity of the hot tub components.

An easy way of detecting high alkalinity in your tub is misty/cloudy water. This is because, at high alkalinity, objects tend to float in the water freely, leading to high chances of particle accumulation. High alkalinity comes with side effects such as:

  • Water pH lock as the pH will be unaffected by further changes in pH. However, high alkalinity can also result in increased pH
  • Blockage of water exits/pipes due to accumulated particles floating in the water
  • The blockage of water results in the circulation of water at a reduced/low rate
  • Components like pipes become affected as a result of defects (e.g., cracks) resulting from high pressure by water current due to blockage in those pipes.

Just like low alkalinity, there are two widely known remedies for high alkalinity which are:

  • Use of muriatic acid
  • Use of dry acid (sodium bisulfate) or any alkaline-level reducer product

Ensure that you look out for your water’s pH on the addition of any of these acids, as it might fall alongside the alkaline level.

What happens if alkalinity is high?

High alkalinity increases the difficulty in changing the pH. High pH, in turn, results in murky or misty water usually accompanied by the formation of scales on the hot tub surface.

Also, your hot tub will not be readily sanitized by chlorine. This could lead to the invasion of disease-causing microbes in the spa.

Moreover, the scale buildup could result in the clogging of the filter and pipes. When the pressure builds up due to the clogs, the filter can easily break down and also affect other components.

How do I lower the alkalinity naturally?

The best way to lower alkalinity is using these three easy steps as described here. The use of chemicals such as muriatic acid and dry acid makes it a lot easier.

Research has shown that the acids reduce alkalinity in water to ideal levels. However, keep your acids diluted during use. Use chemically resistant hand gloves, use protective eyewear. Do not add water to acid, only the other way around, to avoid explosions.

Nevertheless, if you don’t wish to add chemicals to your hot tub, then you can lower the alkalinity naturally by refilling the spa with fresh water with lower alkalinity/pH.

But that method is not easy as the pH would probably need to be altered.

Is it safe to use the hot tub if alkalinity is high?

Keeping enough chlorine (about 3 ppm) in your hot tub as well as the pH balance (at about 7.4-7.6) makes it safe to use the hot tub.

However, your alkalinity needs to be between 80ppm and 120ppm to maintain such levels.

If the alkalinity is off the range, it is not safe to enter the hot tub. When the pH is high you will experience itchy skin and irritation in the eyes.

Moreover, the sanitizer would stop working properly which might encourage the growth of alkaliphiles in the tub. With that, using the spa can cause microbial infection.

So, it is not safe to use your hot tub when the alkalinity is high. Even when it is low, you don’t need to use it.

Is high alkalinity harmful to a hot tub?

Yes, a high alkalinity level is not good for your hot tub. As we know that low alkalinity can corrode the hit tub surfaces, high alkalinity can also affect your hot tub components.

High alkalinity can lead to scale buildup. And if the issue is not controlled it can cause clogging of the filter and pipes. As pressure builds up due to the clogging, the filter can easily get damaged. It can as well affect other components.

Do pH reducers lower alkalinity?

It is widely known that pH reducers lower pH. They, as well, reduce alkalinity as seen in Dry Acid or Muriatic Acid.

Since the two factors are closely related, anything that affects one will also affect the other.

What happens if you get in a hot tub with too much chlorine?

As expected, too much of something is bad. Too much chlorine in your tub will cause it to vaporize and float above your tub’s water as a gas.

The inhalation of this gas can cause breathing failures or airway complications. It can also damage your skin by causing irritations.

Is cloudy hot tub water safe?

No, there is no safety in having cloudy water in your hot tub. Should your hot tub have cloudy water, know that there is a problem. Your hot tub water must be clear.

If the hot tub is cloudy, then it means that the sanitizer is already weak and the water can easily get contaminated. Once the water gets contaminated with disease-causing microbes, it is no longer safe for the users.

That is the major reason why it is not safe to use a cloudy hot tub.

Scales formed in hot tubs contain?

High alkalinity leads to the formation of scales on the walls of the hot tub. These scales contain mainly calcium.

To learn how to remove calcium build-up in three easy steps, check this article.

What is considered high alkalinity?

Highly alkaline water is greater than 150 mg/L and results in scaling. The alkalinity level in your spa should be between 80ppm and 120ppm.

Once the alkalinity level goes beyond 120ppm is it considered high. Though some experts also recommend 150ppm as a safe level, do your best to keep it between 100-120. That is the ideal range.

If it crosses 150ppm, it is highly unsafe for anyone to use. So, always test your spa water to know the water balance.

So, if you are wondering when to lower the alkalinity level, test the water and determine the alkalinity levels. If it’s above 120ppm, try to lower it.

Alkalinity should be lowered when it gives rise to a noticeable high pH level, or in special cases when there are occurrences of scaling in the hot tub.

Is high alkaline water corrosive?

Compared to low alkalinity which accounts for high corrosiveness, highly alkaline water is not corrosive. But it can lead to scale buildups which can clog the hot tub filters.

So, it doesn’t need to be highly corrosive to damage your spa. It can damage your spa by forming scales and cloudy water.


Maintaining balanced alkalinity in your tub can be very delicate. As such, the addition of different chemicals can have drastic effects on your spa. But through the use of the two aforementioned acids, you can be sure to have little or no difficulties in having balanced alkalinity.

However, a drop in alkalinity can lead to a drop in pH. That leads to the use of sodium bicarbonate (baking soda), soda ash, and the addition of oxygen (aeration).

Both sodium bicarbonate and soda ash uses are widely known methods. They are useful because they are capable of maintaining alkalinity balance for a long time. But in case you are not planning to keep the alkaline level balanced for long, you can try aeration. Aeration involves adding oxygen to the water thereby, getting rid of acids of carbon and increasing the pH simultaneously.

In short, ensure that you put alkalinity balanced to ensure a balanced pH and a pleasantly unforgettable experience in your hot tub.

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