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How do you raise the pH in a hot tub without alkalinity? | HotSpring Spas

How do you raise the pH in a hot tub without alkalinity?

One of the most important parts of hot tub upkeep is maintaining the proper pH and alkalinity levels. When the pH in your hot tub is too low, problems such as metal corrosion, high levels of bacteria and burning eyes may occur.


To raise or lower the pH level in your hot tub, test the hot tub’s current pH level and then add the appropriate amount of FreshWater® pH/Alkalinity Up or FreshWater® pH/Alkalinity Down to the water. Repeat the process as needed until your hot tub has reached the correct pH level of between 7.2 and 7.8.


In this article, you’ll find a detailed step-by-step guide to raising the pH in your hot tub. You’ll also find helpful answers to the most commonly asked questions regarding hot tub pH and alkalinity levels.


How do you raise the pH in a hot tub? 

Read on for a step-by-step guide on raising the pH in your hot tub.


Step 1: Test the water. 

The very first thing you’ll want to do before adding any chemicals to the water is to figure out your current pH level. A low pH can cause all sorts of issues for your hot tub, from erosion of plaster and grout to corrosion of metal. Those who sit in your hot tub will likely suffer from dry skin and red eyes as well. The optimal pH level for a hot tub is between 7.2 and 7.8. Anything below 7.2 is considered too acidic, while a pH level above 7.8 is too alkaline and comes with a whole host of other problems.


To test the water’s pH level, you’ll need to use test strips, a liquid test kit or a digital tester. It’s recommended to use products that are specifically meant for pools and hot tubs, for example the Freshwater® 5-way Test Strips. Oftentimes, these products will test more than just pH levels. They’ll also look for levels of chlorine, alkalinity and bromine, among others.


When planning to raise or lower pH levels, be sure to test your alkalinity levels as well. Alkalinity and pH are closely intertwined, and you cannot raise one without raising the other. Your levels of pH and alkalinity will help you decide between FreshWater® pH/Alkalinity Down (sodium bisulfate) and FreshWater® pH/Alkalinity Up (sodium bicarbonate) as an agent to increase your hot tub’s pH level.


Step 2: Choose between pH/Alkalinity Down and pH/Alkalinity Up to optimise your hot tub’s pH level.


It’s important to remember that it’s impossible to raise the pH level in your hot tub without also raising alkalinity. Alkalinity is often referred to as Total Alkalinity, or TA. It measures the amount of alkaline substances in the water, which influences the water’s ability to maintain pH levels. The ideal TA range is 80-120 ppm (parts per million).


Generally, it’s recommended that you use pH/Alkalinity Up to increase your hot tub’s pH level. However, since pH and alkalinity are so closely related, you do not want to use pH/Alkalinity Up if your alkalinity levels are already high. This will result in off-the-charts alkalinity levels that you will then have to correct. So instead, if your alkalinity is already near 120 ppm, you’ll want to opt for pH/Alkalinity Down rather than pH/Alkalinity Up.


Step 3: Turn on the pumps.

Keeping the air valves closed, turn on your hot tub’s pumps. This way, the water will begin to circulate.


Step 4: Add the appropriate amount of pH/Alkalinity Down or pH/Alkalinity Up to the hot tub filter compartment while the jet pump is running.

If your alkalinity is at a low or normal level, use pH/Alkalinity Up. If your alkalinity is already high, go with pH/Alkalinity Down instead. Adding 1 tablespoon per 100 gallons of water will decrease total alkalinity by 20ppm.


If you’ve chosen to use pH/Alkalinity Up, you’ll need to add one tablespoon for every 100 gallons of water that your hot tub holds. This will increase total alkalinity by 20ppm. For example, if your hot tub holds 300 gallons (1136 litres) of water, you’ll add three tablespoons of pH/Alkalinity Up.


Step 5: Allow the water to circulate.

Step away for at least three hours to allow the pH/Alkalinity Down or pH/Alkalinity Up to circulate completely. Do not cover your hot tub and do not leave your hot tub unattended while open.


Step 6: Turn off the pumps.

After at least three hours, it’s time to turn off the pumps and let the water settle.


Step 7: Test the water again.

Now it’s necessary to test the water again in order to see if your pH and alkalinity levels are in the correct range. Ideally, pH levels should be between 7.2 and 7.8, with an ideal range between 7.4 and 7.6. Alkalinity should fall between 80 and 120 ppm.


Step 8: Repeat the process or drain and refill the hot tub completely.

If your pH and alkalinity levels weren’t too far off to begin with, you might be done with the process of raising the pH in your hot tub! However, you may still have a bit farther to go. If levels are close to where they should be, go ahead and repeat the process.


But in the case that alkalinity and pH levels are still far from the ideal range, it may be best to completely drain out your hot tub and refill it. Sometimes, it’s easier to start fresh, rather than continuing to add chemicals over and over again in hopes that you will be successful. For best results, use a hose filter like the Fresh Start® Clean Screen when refilling your hot tub in order to keep contaminants out. Using a metal sequestrant is also helpful for filtering out any metal build-up in the hot tub.


Frequently Asked Questions


Q: How are pH and alkalinity related?

A: To put it simply, pH levels measure the concentration of acid protons in the water. Alkalinity measures the ability of the water to neutralise or buffer acids. Therefore, alkalinity levels affect the water’s ability to maintain pH levels.


Q: Can I raise the pH level in my hot tub without raising alkalinity?

A: No, you cannot raise your hot tub’s pH level without also raising alkalinity. When you raise or lower the pH level in your hot tub, the chemicals will inevitably also affect the water’s alkalinity levels.


Q: How do I lower the pH in a hot tub?

A: You can lower your hot tub’s pH by following the above procedure but with sodium bisulfate, also known as the FreshWater® pH/Alkalinity Down.


Q: How do I raise and lower alkalinity levels?

A: You can raise alkalinity by using sodium bicarbonate, also known as the FreshWater® pH/Alkalinity Up. To lower alkalinity levels, you’ll need to use sodium bisulfate, also known as the FreshWater® pH/Alkalinity Down.


Q: How often should I test my hot tub’s pH and alkalinity?

A: It’s best to test your hot tub’s pH and alkalinity levels once or twice each week.


Q: What happens when pH levels are too high or too low?

A: When pH levels are too high, the chlorine in your hot tub won’t work as efficiently. You may begin to notice calcium deposits on the water’s surface. In addition, the water may become cloudy or dull, with a strong chlorine odour. Also, algae growth is common when pH levels are too high. On the other hand, low pH levels can cause grout and plaster erosion, corrosion of metal parts and issues with dry skin and burning eyes.


Q: What happens when alkalinity levels are too high or too low?

A: High alkalinity levels result in decreased efficiency of chlorine, cloudy water, difficulty stabilising pH levels and constant pH increases even with the use of pH reducer. Low alkalinity levels are associated with corrosion of metal parts in the hot tub, burning eyes and dry skin and rapid pH level fluctuations.

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