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How to Adjust Alkalinity in Your Hot Tub

Back to the Learning Centre By Jon Filson Hydropool Hot Tubs and Swim Spas https://www.youtube.com/watch?v=FGUJIppfFyMProper water balance is essential for maintaining a safe, comfortable, and enjoyable hot tub experience. One of the most crucial aspects of water chemistry is alkalinity, which plays a significant role in stabilizing pH levels and protecting both your equipment and skin. If your hot tub’s alkalinity is too high or too low, it can lead to issues such as skin irritation, cloudy water and over time, potentially damage the tub’s components. In this article, we’ll guide you through everything you need to know about adjusting alkalinity in your hot tub, including: What alkalinity is and why it’s important How to test alkalinity levels How to raise or lower alkalinity levels Common mistakes to avoid At Hydropool, we want to ensure your hot tub is always ready for a relaxing soak. Let’s dive in and learn how to maintain proper alkalinity levels in your hot tub.  What is Alkalinity and Why is it Important? Alkalinity refers to the water’s ability to neutralize acids, which helps keep the pH level stable. In simple terms, it acts as a buffer to prevent rapid shifts in pH levels, keeping your water balanced and safe. It’s actually often called “buffer” in the industry as a result.  Alkalinity is measured in parts per million (ppm), and for hot tubs, the ideal range is typically between 80–120 ppm. If alkalinity levels are too low, the pH can fluctuate, leading to corrosion of your hot tub’s metal components, such as heaters and jets. If it’s too high, it can cause the water to become cloudy and prevent pH adjustments, making it difficult to maintain proper water chemistry.  How Does a Hot Tub Work? How to Test Alkalinity Levels Before you can adjust your hot tub’s alkalinity, you need to test the water to determine the current levels. You can use a few different methods for testing: Test Strips: These are the quickest and easiest method. Simply dip the strip into the water, wait for a few seconds, and compare the colour change to the chart provided with the strips. Most test strips will provide readings for both alkalinity and pH. For a hot tub, water test strips are the least expensive and all you should ever need for water testing. Digital Testers: These handheld devices offer a more precise reading and are often a bit more expensive than test strips. They can give you an accurate measurement of alkalinity and pH with just a small sample of water. Liquid Test Kits: A more traditional method, liquid test kits usually involve adding drops to a water sample to create a colour change. The results are then compared to a colour chart to determine the alkalinity. Regardless of the method, it’s important to test the water regularly (ideally every few days) to ensure the water chemistry remains balanced.  How to Raise or Lower Alkalinity Once you know your alkalinity levels, you can adjust them by adding specific chemicals to the water. Here’s how to do it: How to Raise Alkalinity If your alkalinity is too low (below 80 ppm), you’ll need to raise it to prevent pH swings and protect your hot tub equipment. The best chemical to use for this is alkalinity increaser, which typically contains sodium bicarbonate (baking soda). Here’s how to raise the alkalinity: Calculate the Amount Needed: Follow the instructions on the product packaging, as the amount of alkalinity increaser needed depends on your hot tub’s size. Most containers will come with a set sized scoop that helps with this process. Typically, adding around 1.5 oz (42g) of sodium bicarbonate per 1,000 litres of water will increase alkalinity by about 10 ppm. Add the Chemical: Add the recommended amount of alkalinity increaser to your hot tub water. It’s best to add the chemical gradually and evenly around the perimeter of the tub. Run the Jets: Turn on the jets to circulate the water and allow the alkalinity increaser to dissolve completely. This will take between 15 minutes and half an hour. Don’t use the hot tub during this time.  Retest the Water: After a few hours, retest the water to ensure the alkalinity is within the ideal range (80–120 ppm). If necessary, repeat the process until you reach the desired level.  Adding chemicals is best done slowly and carefully in order to prevent chemical swings in your water.How to Lower Alkalinity If your alkalinity is too high (above 120 ppm), you’ll need to lower it to bring your water chemistry back into balance.  To lower alkalinity, you’ll need pH decreaser (also known as pH-minus or muriatic acid) or an alkalinity decreaser. But just to confuse people, it’s usually called pH decreaser.  Here’s how to lower the alkalinity: Calculate the Amount Needed: Refer to the product’s instructions for the exact amount of pH decreaser needed. Generally, you’ll need around 1.5 oz (42g) of pH decreaser for every 1,000 litres of water to lower alkalinity by 10 ppm. Add the Chemical: Slowly add the recommended amount of alkalinity decreaser to the water while the jets are running to ensure the chemical is evenly distributed. Wait 15 minutes to half an hour.  Retest the Water: After several hours, retest the water to check the alkalinity level. If necessary, add more alkalinity decreaser, but always do so gradually to avoid overshooting your target level. Otherwise you’re caught in a trap of adding then subtracting, adding and subtracting.  Hydropool’s Self-Cleaning Hot Tubs Common Mistakes to Avoid When Adjusting Alkalinity Adjusting alkalinity is a simple process, but there are a few common mistakes you’ll want to avoid: Adding Too Much Chemical: Always follow the manufacturer’s instructions and start with small amounts when adjusting alkalinity. Adding too much chemical quickly can cause the levels to swing too far in the opposite direction. Take your time and get it right. Alkalinity is usually one of the most stable compounds.  Not Testing the Water Regularly: Water chemistry can change over time due to factors like bather load, weather conditions, and the type of chemicals used. Be sure to test your hot tub’s alkalinity and pH each week to keep…