How to Lower Alkalinity in a Hot Tub (5 Steps)?

Hot tubs require a low level of alkalinity to ensure that the water remains safe and clean for use. If the level of alkalinity is high, it puts your hot tub at risk of contamination and eventually green water. So, how to lower alkalinity in a hot tub?

The best way to lower alkalinity in a hot tub is to add pH decreased (minus). Add the correct dose of pH minus and re-test the water in 1 hour to see the changes.

But that’s just the simple answer. Down below we have prepared a short but effective guide that will teach you how to lower alkalinity levels in your hot tub.

What Happens if Alkalinity Is Too High in the Hot Tub?

A high level of alkalinity will reduce the effectiveness of the sanitizers like bromine and chlorine that you add to the water.

Since the sanitizers aren’t effective because of the high level of alkalinity, your hot tub is eventually going to become a breeding pond for all sorts of bacteria, algae, and contaminants.

You will also spend more money trying to fix the green water and other problems that have been caused by high alkalinity.

What Should Be Adjusted First Alkalinity or pH?

The pH decreased will lower the pH levels in your hot tub. If both alkalinity and pH levels are low, then start by fixing the alkalinity leaves. After that, you can fix the pH levels.

There are a lot of methods to increase pH levels after balancing total alkalinity levels. You can use baking soda or soda ash. While these two products do a good job, they aren’t recommended.

Soda ash can also increase the alkalinity levels. If you don’t want to go back and forth with raising and lowering the alkalinity levels you should aerate the water. You can buy aerating devices and attach them to your hot tub. Or, you can turn on the jets to aerate the water.

How to Lower Alkalinity in a Hot Tub (5 Steps)?

The easiest and most effective way of lowering the level of alkalinity in your hot tub water is to add pH decreaser or sodium bisulfate. But there are a few preparatory steps to follow before adding the ph decreaser.

1. Find Out How Much Water the Hot Tub Holds

Find Out How Much Water the Hot Tub Holds

The first thing to do is to know how much water is in the hot tub. This step is vital because the ph decreaser needs to be added in the right amount. The wrong dose will alter the water chemistry and can even the problem worse.

You can know how much water is in the hot tub by knowing how much water the hot tub can hold. You must have already filled the hot tub to its maximum capacity, so all you need to know is how much water your hot tub can hold when filled. Below is a rough estimate based on the different sizes of hot tubs that exist.

  • 2-3 person hot tub – Between 250 gallons and 300 gallons of water
  • 4-6 person hot tub – Between 320 gallons and 500 gallons of water
  • 7-8 person hot tub – Between 550 and 700 gallons of water.

2. Test the Water

Test the Water

You can test the water by taking a sample of the water to a local pool store for professional testing. Or, you can test the water by yourself by purchasing a liquid test kit, a digital tester, or a test strip.

Test strips are more common and easier to use. Dip a test strip in the water and pull it out. Then judge the color on the test strip to the colors on the bottle to get your reading.

The ideal level of alkalinity for a hot tub is between 80 and 150 ppm (parts per million). Some sources will advise leaving the total alkalinity between 100 and 150 ppm (parts per million).

If you have any reading between these numbers, then the level of alkalinity is fine. If the alkalinity is above 150 ppm, then you need to reduce it.

3. Add the pH Decreaser to the Water

Add the pH Decreaser to the Water

The next step is to add the ph decreaser or sodium bisulfate to the water. Ensure the jets are running before you add the ph decreaser. This will help the ph decreaser to be well circulated in the water and prevent the concentration in just one side of the hot tub.

If the jets aren’t running, then it will take a very long time for the ph decreaser to be circulated in the water. And, that can cause the water chemistry to be all off.

Ensure to also add the ph decreaser in the right amount. Follow the instructions on the container regarding the addition of the ph decreaser to the water.

The right amount is to add about 3 ounces (85 grams) of the ph decreaser or sodium bisulfate to 1000 gallons of water to drop the alkalinity by 10ppm (parts per million).

Sodium bisulfate used as ph decreaser comes in powdery form. The powder can be scattered inside the water. You can also take out some water and mix it with the right amount of sodium bisulfate before adding it to the hot tub. It’s always advised that no one should be inside the hot tub while this is being done.

4. Keep the Jets Running

Keep the Jets Running

After adding the required amount of ph decreaser to the water, keep the jets running for 15 to 30 minutes so the water can fully absorb the ph decreaser.

After this, you can turn off the jets and leave the hot tub for a few hours. The hot tub should be left for at least 24 hours after this procedure.

5. Re-test the Water

Re-test the Water

After 24 hours, retest the water with the test strip to check the level of alkalinity. The level of alkalinity should have been lowered. If it’s still not at the required level, then you can repeat this process.

6. Last Resort (Optional)

If you have carried out all the steps above and you still find it difficult to lower the level of alkalinity, then you need to drain and refill the hot tub. Chances are you haven’t drained the hot tub in a while. That’s why the water chemistry is all over the place and difficult to balance.

It’s usually advised to drain the hot tub regularly to prevent a build-up of contaminants that can increase the level of alkalinity.

So drain the tub, clean it, and refill it. After doing that, you should add the chemicals at the right amount so the water chemistry is balanced.

Does Baking Soda Lower Alkalinity in a Spa?

No, baking soda doesn’t lower alkalinity in a hot tub. In fact, baking soda raises the alkalinity in a hot tub.

If you have high levels of TA in your hot tub, then you shouldn’t put baking soda. That will make things even worse. Adding too much baking soda, while having a high level of alkalinity can cause green water.

Except for the alkalinity, baking soda also raises the pH levels. Having high pH and TA levels is something you don’t want. So, never use baking soda when you total alkalinity in your hot tub is high.

Does Vinegar Lower Alkalinity in a Hot Tub? (or White Vinegar)?

No, vinegar doesn’t lower alkalinity levels in a hot tub. Vinegar only lowers the pH levels in a hot tub. But, it’s not recommended to use it.

While vinegar doesn’t lower alkalinity levels it can lower pH levels. But, that can make things worse. I recommend using vinegar only to clean the hot tub. Never put vinegar in the hot tub water you are going to use.

What Causes High Alkalinity in Hot Tubs?

It’s important to know what causes high alkalinity in the first place. This will help us discover how to prevent it and how best to deal with it.

Here are some of the common reasons for high alkalinity in a hot tub.

1. Bodily Residue and Body Care Products

You may not know this but most of the body care products you and your fellow bathers use on your bodies affect the alkalinity in the hot tub. Body care products like body lotion, shampoo, hair gel, perfume oils, sunblock, and the likes alter the pH level and consequently the level of alkalinity in your hot tub.

Most of these body care products have a certain percentage of acidity or alkalinity in their formula. When you soak in the hot tub without washing these products off first, you are directly increasing the ph level of your hot tub. And, that can cause a high level of alkalinity.

2. A High Dose of pH Alkalinity Increaser

Having a high alkalinity reading in your hot tub water isn’t a common problem. Most times, you will find yourself adding an alkaline increaser to the hot tub rather than worrying about reducing the level of alkalinity.

It’s possible you accidentally added a higher amount of alkaline increaser than needed to the hot tub. This will increase the level of alkalinity in your hot tub.

3. Too Many Chemicals

If you are the type that adds different chemicals to your hot tub time after time, then you may be increasing the level of alkalinity in the water. Too many chemicals in the hot tub will increase the total dissolved solids (TDS) in the hot tub.

TDS is a measure of the level of all dissolved organic and inorganic matter in the water. If the level of TDS is high, it can cause a high level of alkalinity.

4. The Water Source

If the level of alkalinity is high, the water source might be the problem. Many of us fill our hot tubs directly with the water from the tap. If you live in areas where the water supply has a high level of alkalinity, then it’s only expected to have a high alkalinity level in the hot tub.

The best way to be sure is to test the water that runs from the tap or contact the water supply company to know the alkalinity reading of the water.

Other causes of high alkalinity levels in the hot tub include food residue in the water and a damaged filtration system. So how can you lower the level of alkalinity in the water? Keep reading to find out.

Related Read: How To Raise Alkalinity Levels in a Hot Tub?

How to Prevent Having a High Level of Alkalinity in the Hot Tub?

The best way to battle a high alkalinity level in the hot tub is to prevent it in the first place. Here are a few tips to keep the level of alkalinity at the right balance.

1. Do Not Mix Chemicals

Many hot tub owners are fond of mixing chemicals in the hot tub. This is one scenario where more isn’t always merrier. Too many chemicals in your hot tub can alter the ph level and increase the level of alkalinity in the water.

Mixing chemicals is also not a good idea health-wise because these chemicals have different formulas and some of them are not to be mixed. If you must add different chemicals or sanitizers to the hot tub, ensure to add them one after the other. You should also space out the time frame, so the chemicals don’t react.

2. Test the Water Regularly

Hot tub maintenance is the best way to avoid low alkalinity. Ensure to test the ph level and water chemistry of the water in the hot tub regularly. This will indicate when you have low ph levels or high ph levels and also when you need to add or reduce the level of chemicals in the water.

3. Allow the Water to Circulate After Adding Chemicals and Sanitizers

When you add chemicals or sanitizers to the water, turn on the hot tub and let the jets run for about 15 to 30 minutes. This allows the chemicals to be well circulated in the water.

If you don’t turn on the jets, the water will remain stagnant and the chemicals will be concentrated in just one part of the water. This can cause the water chemistry to be all over the place and it can also increase the level of alkalinity in the water.

4. Use a Hose Filter

Always use a hose filter whenever you are refilling your hot tub. A hose filter will prevent solids and other contaminants from getting into the hot tub.

This will help to control the level of alkalinity especially if you live in areas where the water supply has a high alkaline reading.

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