How do you lower alkalinity in a hot tub naturally?

Having the right alkalinity level in your hot tub water is important for balancing pH and preventing corrosion or scale buildup. But sometimes the alkalinity rises too high. Here’s how to lower it naturally, without chemicals.

What is Alkalinity in a Hot Tub?

Alkalinity refers to the amount of bicarbonates, carbonates, and hydroxides in the water. These compounds act as buffering agents that help prevent large pH fluctuations when acids or bases are added to the water.

The ideal alkalinity range for most hot tubs is 80-120 ppm (parts per million). If the alkalinity is too low, below 60 ppm, the pH will be unstable and difficult to adjust. Too high, above 180 ppm, and the water will be prone to scaling and cloudiness.

Why is High Alkalinity a Problem?

High alkalinity causes a few issues:

• Makes pH difficult to adjust – the buffers resist pH change
• Can lead to scale formation on hot tub surfaces and equipment
• Causes cloudy water from precipitation of carbonates
• Potential corrosion problems despite high pH readings

That’s why it’s important to monitor and control alkalinity within the ideal 60-120 ppm range. Here are some ways to lower high alkalinity levels naturally.

Dilute the Hot Tub Water

The simplest way to lower alkalinity is to partially drain the hot tub and add fresh water. This dilutes the concentration of bicarbonates and carbonates. Drain 30-50% of the water and refill if the alkalinity is very high.

Be sure to retest and balance the pH and sanitizer levels after diluting the water. The new water chemistry may require adjustments.

Use a Pre-Filter when Filling

Certain types of filters can remove some of the alkalinity when filling up the hot tub:

• Deionizing filter – Uses a resin bead exchange process to remove bicarbonates, carbonates, and other ions.
• Reverse osmosis filter – Forces water through a semipermeable membrane to exclude dissolved salts.
• Carbon block filter – Can adsorb some alkalinity compounds through a granular activated carbon medium.

Using filtered water when diluting and refilling will help prevent the alkalinity from rebounding quickly. Be sure to test and confirm the water’s alkalinity before and after filling.

Add Acid to Lower pH and Alkalinity

Adding an acid directly lowers both the pH and alkalinity in one step. As the acid reacts with the alkalinity buffers, it gradually consumes them while lowering the pH.

Dry acid choices like sodium bisulfate (pH/alkalinity down) or muriatic acid work well. Start by adding 1/2 ounce per 100 gallons and retest after a few hours. Repeat as needed until the alkalinity falls into the desired range. Be careful not to overshoot and lower it too far.

Use Baking Soda to Maintain pH

One risk of using acid is that the pH can drop too low. To counteract this, add baking soda at the same time. The baking soda will raise pH back up while the acid brings down the alkalinity.

Aim for a ratio of around 2:1 acid to baking soda. For example, use 2 ounces of acid combined with 1 ounce of baking soda. The exact ratio needed depends on the starting pH and alkalinity levels.

Replace Some Hot Tub Water Regularly

Partial water changes help lower alkalinity over time by diluting it bit by bit. Changing out 10-25% of the water 1-2 times per month prevents alkalinity from creeping up. This regular maintenance also removes other dissolved contaminants.

Test the alkalinity after each partial change to see how much it drops. You may need to supplement with acid treatments periodically as well.

Use Preventive Measures

Here are some ways to prevent high alkalinity in the first place:

• Add alkaline buffers only when needed according to tests.
• Use a water softener if the source water has high natural alkalinity.
• Inspect plumbing for corrosion and replace if needed.
• Choose low-alkalinity sanitizer options.
• Clean filters regularly to remove debris before it decays.

Starting with a proper foundation of balanced water and well-maintained equipment goes a long way.

Remove Scale Buildup

High alkalinity water can leave scale deposits on hot tub surfaces and pipes. Removing these can help lower the alkalinity since the scale is made up of the offending compounds.

Use a pumice stone to gently scrub off surface scale on acrylic. For plumbing scale, there are some cleaners that can dissolve and remove deposits.

Preventing scale in the first place is ideal, but periodically descaling can help manage alkalinity levels.

Use a Hot Tub Ozonator

An ozonator produces ozone gas that oxidizes and destroys some alkalinity compounds. The effects are modest, but an ozonator can help reduce scaling potential and gradually lower bicarbonates.

Use ozone along with occasional acid treatments for an effective one-two punch against high alkalinity. Proper ozone levels are key – too much can be corrosive.

Change to Biguanide Sanitizer

Switching to a biguanide product like BaquaSpa for sanitization avoids addition of sodium bicarbonate, which increases alkalinity. Biguanides do not raise pH or alkalinity like chlorine or bromine.

Transition carefully by fully removing all remnants of the old sanitizer first. Once converted, biguanide use can help control alkalinity creep.

Adjust Bromide Ion Levels

Bromide is needed to activate bromine tablets. But too much bromide in the water can contribute to higher alkalinity. Keep an eye on the bromide level and adjust to the minimum needed per the sanitizer instructions.

Bromide test strips are needed for an accurate reading. Reduce bromide additions if the level is above the target and perform partial water changes to dilute as needed.

Use a Water Clarifier

Cloudy hot tub water from high alkalinity is unpleasant. A clarifying agent can help group tiny particles together so they can be captured by the filter.

Clarifiers containing polymers or quartz bond with microparticles to clear up the water. This also removes some traces of alkalinity compounds.

Test alkalinity levels after using a clarifier to see if it provides a measurable reduction. Keep using it regularly if it helps lower the level over time.

Conclusion

Lowering high alkalinity in a hot tub takes some patience and persistence. There is no instant fix, but combining several methods allows a gradual return to proper alkalinity:

• Dilute the water with partial changes
• Use filtered water for refilling
• Add acid to lower pH and alkalinity
• Supplement with baking soda to maintain pH
• Remove scale deposits
• Employ preventive measures
• Consider ozone and biguanide sanitizer
• Clarify cloudy water

Test alkalinity and pH a couple times per week to ensure the levels remain stable. Be consistent with your plan and you can get that hot tub water back to perfect balance.

Method	How It Works
Dilute Water	Partial drain and refill lowers concentration of alkalinity compounds
Pre-Filter	Specialized filters like deionizing remove some alkalinity when filling
Add Acid	Acid reacts with and consumes alkalinity buffers
Baking Soda	Counters pH drop from acid addition
Regular Changes	Frequent partial changes prevent alkalinity creep
Prevention	Proper maintenance and water balance from the start
Remove Scale	Eliminates deposited alkalinity compounds
Ozonator	Oxidation destroys some bicarbonates over time
Biguanide Sanitizer	Avoids addition of sodium bicarbonate
Clarifier	Removes traces of alkalinity by bonding particles

Getting alkalinity down takes time and effort, but it’s important for water balance. Pay close attention to alkalinity and pH test readings throughout the process. Be patient, consistent, and thorough to safely reduce elevated alkalinity levels. Your patience will pay off with clean, clear, balanced hot tub water.