How To Lower The Alkalinity In A Hot Tub

A perfect hot tub soak is done in warm, crystal-clear water, and alkalinity is integral to achieving this. It helps resist big pH swings and keeps your water balanced. But too much alkalinity can cause cloudy water and make it difficult for the sanitizer to work properly. So how do you lower the alkalinity in your hot tub?

Acid-based alkalinity-reducing chemicals are added to the spa water to lower the alkalinity. Using test strips, the hot tub can be checked and dosed according to the adjustment chemical’s instructions. For best results, adjust in small increments and allow some circulation time between adjustments.

Highly alkaline hot tubs do not let the chlorine or any other sanitizer do its work efficiently—imagine the germs and bacteria having a party in your hot tub! To prevent this from happening, it is crucial to maintain balanced alkalinity. So, let’s find out how to balance the alkalinity in your hot tub and a few tips to keep it healthy and clean.

What is Alkalinity?

Alkalinity is the ability of water to resist changes in pH. In other words, it’s a buffer that keeps your hot tub’s pH levels stable, so adding chemicals like chlorine doesn’t change the pH levels drastically.

Alkalinity is measured by the amount of bicarbonate (HCO3-), carbonate (CO3-2), hydroxide (OH-), and a few other ions in the water and is measured in parts per million (ppm). The ideal alkalinity range for hot tubs is between 80-120 ppm.

What’s the Difference Between Alkalinity and pH?

Analysis of the PH and chlorine of the water in a swimming pool in Summer.

The pH level of a hot tub is the measure of its acidity or alkalinity. It’s measured on a scale of 0 to 14, and 7 is neutral. So, the ideal pH range for hot tubs is 7.2-7.6. Any lower than 7, the water becomes irritating, and any higher becomes a breeding ground for bacteria and other contaminants.

Alkalinity is what helps to keep the pH levels stabilized; it’s the measure of salts that absorb the acid or base so that the pH level doesn’t fluctuate too much when any external factors come into play.

For example, when you add chlorine to a spa with low alkalinity, the pH level drops below 7. As a result, the water becomes corrosive, damages the plumbing in your hot tub, and irritates your skin and eyes.

Alternatively, when you add chlorine to a highly alkaline spa, the salts absorb the sanitizing effect of chlorine. But unfortunately, the contaminants aren’t killed off properly, which can result in cloudy water, spa scale, and even algae growth in the long run.

So essentially, alkalinity is the bodyguard of your hot tub. It buffers the pH levels and creates a pleasant, balanced environment for you to enjoy an optimal hot tub experience.

What Causes High Alkalinity in a Hot Tub?

High alkalinity happens when you do not refill or replace the water in your hot tub often enough. Minerals, like calcium and magnesium, start to build up in the water over time, raising the alkalinity levels.

Now the question is, where do these salts come from?

1. The People in the Hot Tub

There are several sources, but the biggest source is YOU! For example, when you or your family bathe in your hot tub, you bring sweat, body oils, lotions, sunscreens, and many other things that contain minerals.

These minerals then build up in the water and gradually increase the tub’s alkalinity levels beyond the standard range. An easy way to avoid this is showering before getting into the hot tub.

2. Used-Up Chemicals

Another related factor is too many chemicals. When you don’t change the water enough, you tend to overuse the chemical to keep the water clean. When the chemicals are used, they leave a mineral residue in the water called Total Dissolved Solids or TDS. This residue also raises the alkalinity levels.

3. Water Source

Some places have naturally mineral-rich waters, resulting in higher alkalinity levels in the hot tub. A common indication of this type of water is a metallic taste or white deposits on your tub’s surface and plumbing.

If you suspect your tap water is mineral rich, it may be a good idea to have the water tested or ask the local water department for more information.

4. Inappropriate Chemical Dose

Last but not least, it is when you accidentally add too much or too few chemicals to your hot tub. For example, an overdose of baking soda or soda ash can raise the alkalinity in your hot tub. Or the underdose of muriatic acid or chlorine can cause alkalinity levels to stay high.

If you suspect a chemical-related issue is causing the high alkalinity in your hot tub, check the instructions on how to dose them properly. And then fix it by using the appropriate chemical.

How to Lower a Hot Tub’s Alkalinity

An acidic compound, such as sodium bisulfate or muriatic acid, can decrease your hot tub’s alkalinity. This is because these acids bind with the bicarbonates to form carbon dioxide and lower the alkalinity levels. 

However, a properly formulated pH-reducing chemical (on Amazon) is a better choice, as it’s designed specifically for hot tubs and will not compromise the water quality.

Always follow the manufacturer’s instructions given on the product’s label and be extra careful when using pH decreasers, as over-dosing can drastically drop the pH level and make your hot tub water very corrosive.

It’s highly recommended to first test the alkalinity levels with the help of a liquid water test (on Amazon) or test strip (on Amazon). (The normal range is 80-120 ppm, however, up to 150 ppm is also acceptable for some hot tubs.) 

  1. Measure precisely how much pH decrease you need to use, and then pour it around the tub’s circumference while the jets run.
  1. Turn off the jets after 10-15 minutes and let the water sit for an hour or overnight if you have time.
  1. Next, test the alkalinity levels again; if it’s still too high, you can safely repeat the process until it’s in the normal range.
  1. Lastly, adjust the pH level to 7.2-7.8 and add chlorine to maintain a healthy hot tub.

Another simple but effective way to reduce the alkalinity levels is water change. You can either drain the entire tub or do a partial drain. However, this option is viable when your tap water is balanced and isn’t the culprit behind the high alkalinity levels.

Tips for Maintaining a Balanced Alkalinity

Proper water chemistry is the key to a healthy hot tub, and it’s not just about balancing the alkalinity levels. But everything is related, and when you ensure that one factor is balanced, it automatically helps the others. 

Here are some quick tips to keep your hot tub water’s alkalinity in check:

Regular Water Changes

Make sure you drain and refill your hot tub at least every three months, depending on the usage. Every time, run a cleaning cycle (pH decrease, chlorine, or non-chlorine shock) to eliminate any dirt, debris, and mineral residue.

Test the Water Regularly

At least once a week, test the alkalinity (and other water chemistry parameters). It’s essential to identify any problems early and prevent them from getting out of hand.

Use Liquid Test Kit

Spa Jacuzzi Hot tub water quality testing

Test strips are quick and easy to use, but they’re not as accurate and may not detect tiny changes in the water chemistry.

So, buy a liquid test kit, collect a water sample in a small container and test it once it cools down to room temperature. The cost difference is insignificant and worth it for reliable results.

Don’t Mix Chemicals

Never add more than one hot tub chemical at a time, as you can’t predict what difference it will make. So, give at least 15 minutes to each chemical, test the water again, and then add the next chemical.

Get Your Tap Water Tested

If you’re using tap water for your hot tub, get it tested by your local water authority. It’ll be much less of a hassle to balance the hot tub chemistry when you already know the levels of minerals and other constituents in the water.

Leave a Comment