How to Lower Alkalinity in Hot Tub: A Guide to Hot Tub Water pH

Nothing is more luxurious and relaxing than soaking in a tub’s bubbles and hot water after a stressful day at work. However, you can’t just take a dip any time you feel like it. Owning a hot tub also requires proper upkeep.

One of the most crucial tasks of maintaining a hot tub is ensuring the correct chemical composition of the water. One chemical aspect you need to keep an eye on is how to lower alkalinity in hot tubs and keep it well-balanced.

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What Is pH?

The pH or power of hydrogen is the hydrogen ion concentration in the water that determines if it’s considered basic, acidic, or neutral. An acidic water level ranges from 0 to 7, while 7 is neutral, and 7 to 14 pH is deemed basic.

That said, your hot tub water should have a pH ranging from 7.4 to 7.6. As it is, anything can change the pH level of the water in your hot tub, especially if the alkalinity level is incorrect.

Similar to unbalanced alkalinity, if the pH level is beyond the ideal range, it can corrode the metal parts of the tub.

What Is Alkalinity?

Alkalinity is the amount of dissolved alkaline substances found in water that helps neutralize the acid. It is also called the buffer since it helps balance the pH level in your hot tub water and resist extreme changes.

Ideally, the total alkalinity range of your hot tub water should be around 80 to 120 parts per million (PPM). An unbalanced alkalinity level in your hot tub may have an unfavorable effect on the water’s appearance. It may also cause skin dryness.

How Can Incorrect Alkalinity Level Affect the Hot Tub Water?

High or low alkalinity levels harm your spa and your skin, and the low range is riskier between these two. When the alkaline level is low, it will be hard for the water to neutralize the acids, causing rapid pH changes and turning it green.

Keeping the alkaline at a low level can cause corrosion on your hot tub’s internal equipment, negatively affecting its surface. Besides turning the water green, a high alkaline level can lessen the effectiveness of your water sanitizer, increasing the pH level.

High pH levels can cause calcium build-up, scale formation, and cloudy water. The yellowish flakes on the water from calcium can impact the jet’s performance and equipment negatively. You will need to deep clean the hot tub to remove mineral deposits and prevent further damage.

What Causes High Alkalinity?

Most hot tub owners conduct regular draining and cleaning of their spas every three to four months to prevent any build-up. However, there are still other causes for the increase in the alkaline level of your hot tub water, including the following:

Human Error

Sometimes, you may cause a high alkaline level in your hot tub water if you have added too much baking soda or alkalinity increaser.

Sweat and Other Body Stuff

You might have forgotten to take a shower in your excitement to jump right into the hot, bubbling water of your spa. Body lotions, hair gels, perfumes, sunblocks, and other things you use on your body can increase the alkaline level when mixed with hot tub water.

Too Many Chemicals

In your quest to have well-balanced water in your hot tub, you might be adding too many chemicals without realizing it. You can prevent this issue by draining and cleaning the hot tub quarterly or every three to four months.

Water Source

Another reason for the high alkalinity level may be your water source. You may ask for water reading from your local water district so you can make the necessary adjustments.

How To Lower Alkalinity in Hot Tub

One of the quickest ways to reduce the alkalinity in the hot tub water is by adding sodium bisulfate or a pH-decreasing solution. As mentioned above, alkaline and pH may differ, but they work together to provide well-balanced hot tub water.

Before doing anything, know the water capacity of your hot tub first, then follow the steps below.

1. Hot Tub Water Testing

Know the current alkalinity level of your hot tub water by using a test strip or a liquid test kit before you put anything in your spa. This way, you will know if you need to lower the alkaline level or not. You should try to reach at least 100 ppm. We recommend using AquaChek 7-Way Pool and Spa Test Strips.

AquaChek Silver 7-in-1 Test Strips are a top-rated choice for hot tub owners seeking reliable water quality management. These easy-to-use strips test pH, total and free chlorine, bromine, alkalinity, hardness, and cyanuric acid with impressive accuracy—no messy drops required. Just dip, wait 15 seconds, and compare the colors to the chart on the bottle.

Ideal for lowering alkalinity and balancing hot tub water, these USA-made strips are trusted by professionals for their precision, vibrant color indicators, and proven consistency. A smart, hassle-free solution to keeping your water clean and safe.

2. Add pH Decreaser

Sprinkle about 85 grams or three ounces of sodium bisulfate powder in 1000-gallon hot tub water to lower the alkalinity by 10ppm. Ensure that the hot tub is running as you sprinkle the ph decreaser powder for quicker and more effective mixing.

Allow the hot tub to circulate for at least 20 minutes before turning it off. The combined acid and water help reduce the total alkalinity and balances the pH level. We recommend using SpaGuard pH Decreaser.

SpaGuard pH Decreaser is a highly effective solution for lowering both pH and total alkalinity in your hot tub water. With a fast-acting formula, it helps prevent cloudy water and scale buildup while protecting spa equipment from damage caused by high pH levels.

This easy-to-use product improves water clarity, enhances sanitizer efficiency, and ensures a comfortable soaking experience. A must-have for maintaining balanced, healthy spa water with minimal effort.

3. Retest The Water

Allow the sprinkled sodium bisulfate to dissolve and mix with the water for an hour before retesting. Leave the hot tub uncovered to allow the water to breathe, release chemical odors, and protect the cover from chemical smell build-up.

Make the necessary adjustments as needed based on the test results. Repeat the process if the alkalinity level is still high. Once you have achieved the appropriate alkalinity level, let it rest for 24 hours and do another test to ensure the level is still the same.

How To Increase Alkalinity in Hot Tub

Too much pH reducer addition will lower the alkalinity below its appropriate level, requiring you to increase its reading. You can increase the alkalinity level of the hot tub water by adding the right amount of sodium bicarbonate.

Add 2.25 ounces of sodium bicarbonate for every 1000-gallon of water to help increase alkalinity by 10ppm. Turn on the spa for 20 minutes as you sprinkle the powder on the tub’s edges before turning it off, allowing it to rest for an hour.

Retest the water, and leave it overnight once you have reached your target alkalinity level. Repeat the testing the following day to confirm if the reading is still the same.

Which Should You Adjust First?

As you can note from the above information, baking soda or sodium bicarbonate is an alkalinity increaser. When you use it, and the alkalinity readings are below the recommended levels, increase the alkalinity first.

Retest the water and see if the readings have improved. If you need to increase the pH level, just add soda ash or sodium bicarbonate.

Does Baking Soda Lower Alkalinity In Hot Tub?

Baking soda is a common household product with many uses, but does it actually lower alkalinity in hot tubs? Let’s explore this topic in detail.

Hot tub owners often face the challenge of maintaining proper water chemistry to ensure a safe and enjoyable soaking experience. One important aspect of water chemistry is alkalinity, which refers to the water’s ability to resist changes in pH. High alkalinity can lead to issues like cloudy water, scaling, and difficulty in balancing pH levels.

Baking soda, also known as sodium bicarbonate, is sometimes suggested as a remedy for high alkalinity in hot tubs. While baking soda can indeed raise pH levels in water, its effectiveness in lowering alkalinity is limited.

Baking soda acts as a buffer, meaning it can help stabilize pH levels by absorbing excess hydrogen ions and preventing rapid fluctuations. However, it primarily affects pH rather than alkalinity. In other words, while baking soda can raise pH levels if they are too low, it may not significantly reduce alkalinity if it is too high.

To lower alkalinity in a hot tub effectively, it’s essential to use products specifically designed for that purpose, such as alkalinity decreasers or pH reducers. These products are formulated to target alkalinity levels directly, providing more reliable and precise results.

If you suspect that your hot tub’s alkalinity is too high, it’s best to test the water using a reliable water testing kit. This will allow you to determine the current alkalinity level accurately. Based on the test results, you can then take appropriate measures to adjust the alkalinity to the desired range.

In addition to using specialized chemicals, other methods for lowering alkalinity in a hot tub include dilution with fresh water and aeration. Dilution involves partially draining the hot tub and refilling it with fresh water, which can help reduce alkalinity levels over time. Aeration, such as running the jets or using an air pump, can also help by promoting the release of carbon dioxide from the water, which can lower alkalinity.

In summary, while baking soda may have some limited impact on alkalinity in hot tubs due to its buffering properties, it is not the most effective solution for lowering alkalinity. For best results, it’s recommended to use products specifically designed for adjusting alkalinity levels and to rely on accurate water testing to guide your maintenance efforts.

Will Chlorine Lower Alkalinity In Hot Tub?

Chlorine is primarily used in hot tubs to sanitize the water by killing bacteria, algae, and other microorganisms. It does this by breaking down into hypochlorous acid, a powerful disinfectant that neutralizes harmful contaminants.

While chlorine is effective at sanitizing hot tub water, its impact on alkalinity is minimal. Chlorine is not specifically designed to lower alkalinity levels in water. Instead, its primary function is to sanitize and disinfect.

However, indirect effects of chlorine on alkalinity may occur under certain circumstances. For example, if the hot tub water contains excessive amounts of chloramines, which are formed when chlorine combines with organic contaminants like sweat, body oils, and urine, it can lead to fluctuations in pH and alkalinity levels. High levels of chloramines can contribute to a phenomenon known as “chlorine lock,” where the chlorine becomes less effective at sanitizing the water due to high levels of combined chlorine.

In such cases, addressing the underlying issue of chloramine buildup may indirectly help stabilize alkalinity levels. This can be achieved by “shocking” the hot tub with a higher-than-normal dose of chlorine to break down chloramines and restore proper sanitation levels. However, it’s essential to follow manufacturer instructions and safety guidelines when shocking a hot tub to avoid overchlorination or other adverse effects.

To directly lower alkalinity levels in a hot tub, it’s best to use products specifically formulated for that purpose, such as alkalinity decreasers or pH reducers. These products are designed to target alkalinity levels directly, providing more effective and precise results than chlorine alone.

Regular water testing is essential for monitoring alkalinity levels in your hot tub and ensuring they remain within the recommended range. This can be done using a reliable water testing kit, which will provide accurate readings of alkalinity and other important water chemistry parameters.

In summary, while chlorine is an effective sanitizer for hot tub water, its impact on alkalinity levels is minimal. To lower alkalinity levels in a hot tub, it’s best to use products specifically designed for that purpose and to rely on accurate water testing to guide your maintenance efforts.

Lower alkalinity in a hot tub without lowering pH

Lowering total alkalinity in a hot tub without significantly lowering pH can be challenging, as most chemicals that reduce alkalinity (such as pH decreasers or muriatic acid) also tend to lower pH at the same time. However, you can manage this with a controlled process called aeration after acid adjustment.

Here’s how to lower alkalinity without lowering pH too much:

Step-by-Step Process:

1. Test the Water:
   • Use test strips or a liquid test kit to check total alkalinity (TA) and pH.
   • Ideal TA: 80–120 ppm
   • Ideal pH: 7.2–7.8
2. Add a pH/Alkalinity Decreaser (e.g., Sodium Bisulfate or Muriatic Acid):
   • Add small amounts (per product instructions) to bring alkalinity down gradually.
   • This will also lower your pH initially—don’t panic!
3. Aerate the Water to Raise pH Back Up:
   • Turn on jets, waterfalls, air blowers, or add an air stone to introduce oxygen.
   • This raises pH without affecting alkalinity.
   • Let the hot tub run for several hours, then retest.
4. Repeat as Needed:
   • If TA is still high, add a bit more acid, then aerate again.
   • Continue testing every few hours until TA is in range and pH stabilizes.

Why It Works:

• Acid lowers both TA and pH
• Aeration raises only pH, so you can restore your pH level without affecting the now-lowered TA

What Not to Use:

• Baking soda – it raises alkalinity.
• Vinegar – not recommended for hot tubs due to impurities and potential plumbing issues.

Hot Tub Maintenance Tips

Here are some essential Hot Tub Maintenance Tips to keep your spa clean, safe, and running efficiently:

Test Water Regularly

Use test strips or a digital tester at least 2–3 times a week to monitor:

• pH levels (ideal: 7.4–7.6)
• Alkalinity (80–120 ppm)
• Sanitizer levels (chlorine, bromine, or alternative)
• Calcium hardness and cyanuric acid (if applicable)

Balance Your Water Chemistry

Unbalanced water can cause cloudy water, skin irritation, or damage to your hot tub.

• Use pH increasers or decreasers as needed.
• Adjust alkalinity first, then fine-tune pH.
• Shock your water weekly with an oxidizer to kill bacteria and remove organic contaminants.

Clean the Filter Monthly

A clogged or dirty filter strains your pump and reduces water quality.

• Remove and rinse the filter with a hose every 2–4 weeks.
• Use a filter cleaner once a month for deep cleaning.
• Replace the filter every 12–24 months, depending on usage.

Drain and Refill Every 3–4 Months

Over time, TDS (total dissolved solids) build up and affect water clarity.

• Completely drain and refill your hot tub every 3–4 months.
• Clean the shell and jets before refilling.
• Add fresh chemicals and balance water immediately after refilling.

Wipe Down the Shell and Waterline

Use a non-abrasive spa cleaner or vinegar-water solution to remove scum lines and grime buildup.

• Clean jets, headrests, and spa covers regularly to prevent mildew.

Maintain the Spa Cover

A well-maintained cover keeps debris out and reduces heat loss.

• Rinse and wipe down the cover monthly.
• Use a UV protectant to prevent cracking or fading.
• Remove snow, rain, and standing water promptly.

Check Water Levels and Jets

• Maintain water level above the skimmer line to avoid pump damage.
• Periodically check that jets are clear and working properly.

Watch for Warning Signs

Cloudy water, foamy surface, foul odor, or error codes on your control panel may indicate:

• Chemical imbalance
• Dirty filters
• Equipment issues
  Address these signs promptly to avoid costly repairs.

Bonus Tip: Use a Hot Tub Maintenance Schedule

Create a simple checklist for daily, weekly, monthly, and quarterly tasks to stay organized and consistent.

Frequently Asked Questions

Maintain the Correct Alkalinity Level of Your Hot Tub

To sum up, there are a few key points you need to remember about how to lower alkalinity in hot tubs and maintain chemical balance. First is to allow the water to circulate for 30 minutes after adding a chemical before doing another test. For more accurate readings, let the water rest overnight before testing.

The ideal alkalinity range is between 80 and 120 ppm, while a neutral pH level is between 7.4 and 7.6. Also, add chemicals with 15-minute intervals, allowing it to rest without cover. Lastly, change the hot tub water quarterly.

For accurate test results, place your water sample in a clean cup, let it cool to room temperature, and use a test kit for precise results.