How to Lower Alkalinity in a Hot Tub

There's nothing quite like relaxing in a warm, bubbling hot tub at the end of a long day or during a weekend escape. Before you dive into that oasis of relaxation, it's essential that the water is chemically balanced to ensure your comfort and safety.

One important element to monitor is the alkalinity, which can influence the effectiveness of sanitizers and the overall health of the water. 

In this post, we explore the world of hot tub chemistry and guide you through the process of lowering alkalinity in your hot tub, ensuring your sanctuary remains a haven of relaxation and rejuvenation. Hint: it’s very similar to reducing alkalinity in a pool.

So, let's dive in together to keep your hot tub's water sparkling and skin-friendly!

What Is Alkalinity?

Alkalinity refers to the capacity of water (or other liquids) to neutralize acids. In other words, it's a measure of the water's ability to resist changes in pH when acids or bases are introduced. 

Keep in mind that alkalinity is not the same as pH. While pH measures the acidity or basicity of a solution, alkalinity simply refers to the capacity of water to neutralize acids. For a more detailed discussion of these two phenomena, check out our blog post on low pH and high alkalinity in the pool.

What Causes High Alkalinity in a Hot Tub?

Here are three common culprits that cause high alkalinity:

Adding Too Many Chemicals

We all want to keep our hot tubs clean and safe. However, we can all occasionally go overboard with chemicals. Adding excessive amounts of chemicals like pH increasers, alkalinity increasers, or even sanitizers can lead to high alkalinity levels in your hot tub water.

To avoid this problem, be sure to follow the manufacturer's guidelines for adding chemicals and test your water regularly. This way, you'll know exactly what your hot tub needs and can avoid throwing off the delicate water balance.

Bodily Fluids and Personal Care Products

Believe it or not, our own bodies can contribute to high alkalinity in hot tubs. Sweat, sunscreen, lotion, and other personal care products can increase the water's total alkalinity. 

To minimize the impact of these products, try rinsing off before entering the hot tub. It's also a good idea to limit the use of lotions and sunscreens when you know you'll be soaking in the hot tub later.

The Water Source

Sometimes, the cause of high alkalinity in your hot tub can be traced back to the water source itself. If your tap water is high in minerals like calcium, it can increase the total alkalinity of your hot tub. This is especially common in areas with hard water.

To address this issue, consider using a pre-filter when filling your hot tub, which can help remove some excess minerals.

Why Does a Proper Alkalinity Level Matter?

High alkalinity can lead to cloudy water, scaling, and reduced effectiveness of sanitizers. On the other hand, if the alkalinity is too low, it can cause corrosion and staining. Achieving the right balance is crucial for the health and longevity of your hot tub.

Steps to Bring Down the Alkalinity in a Hot Tub

If the alkalinity is too high in your hot tub, here are the steps to follow to bring levels back into balance:

Step One: Test the Water

Before correcting the alkalinity, you must know exactly what you're working with. Use a reliable hot tub water test kit or test strips to check the pH, alkalinity, and sanitizer levels. Ideally, you want your total alkalinity to be between eighty and 120 ppm (parts per million) and your pH levels between 7.4 and 7.6 for a perfect balance. 

Step Two: Add a pH Decreaser

One of the easiest ways to lower alkalinity is using a pH decreaser, which is readily available at local pool and spa supply stores. The most common type of pH decreaser contains sodium bisulfate or muriatic acid.

To determine the right amount to add, follow the instructions on the product label. Usually, it is recommended to add 725.75 grams of sodium bisulfate or 1.3 quarts muriatic acid for every 10,000 gallons of water to drop the alkalinity by ten ppm. 

Mix the chemical pH decreaser with water in a separate bucket and let it dissolve before adding it to the tub. Turn on the hot tub’s jet and slowly add the mixture to the center of the hot tub. 

Step Three: Wait and Retest

Let the water sit for a few hours (ideally three to six hours) to give the chemical time to work. Then, use your test kit or test strips to recheck the alkalinity. If it's still too high, repeat steps two and three until you reach the desired level. 

Time to Soak and Relax

Proper care of a hot tub takes some patience, but the results of your efforts are so worth it. If you are unsure of what needs to be done to keep your hot tub water healthy and safe to soak in, call the Pool Care Guy for help!