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Why Does The Chlorine In My Hot Tub Disappear?

Chlorine is very important in a hot tub as it kills any bacteria, fungi and other nasties in your pool. It acts as a sanitizer. However, the chlorine might keep dropping every now and then. This can be quite frustrating while you are enjoying yourself in the hot tub. Due to this, you might wonder, why does the chlorine in my hot tub disappear?

Chlorine breaks down in heat faster due to which it can disappear from the hot tub in summer. Another reason for chlorine disappearing can be chlorine lock. It occurs due to excess cyanuric acid in the water. If you aren’t draining the hot tub enough then too much stabilizer can cause the chlorine levels to drop significantly. Unbalanced PH level also results in chlorine lock.

A low level of chlorine makes you and your family vulnerable to disease when using the hot tub. In this article, I discuss more on chlorine lock, it’s dangers and possible solutions. Reading the full article to know how you can solve this issue. So, without further ado, let’s get right to it. 

What Is A Chlorine Lock?

Chlorine lock is a phenomenon that occurs when there is too much cyanuric acid in the water. This makes the chlorine useless and no matter how much of it is added, it still doesn't work. Too much of a stabilizer breaks down the chlorine making it unable to sanitize the water. Chlorine lock also creates imbalanced chemical levels which makes the hot tub unsafe to use.

Cyanuric acid is a stabilizer that helps shelter the chlorine from the direct ray of the sun. The UV rays break down the chlorine faster than usual. Thus, a stabilizer is very much needed in your hot tub. However, too much of it can cause side effects as the cyanuric acid can also break down the chlorine, rendering it useless.

How To Fix Chlorine Lock?

When you find out you have a chlorine lock in your hot tub, the first thought that comes to your mind is how you can fix it. There are a few ways that work best to deal with chlorine lock. Let's have a look at them.

Partially Draining

To make the chlorine in your hot tub active again you can partially drain the water. This will remove some of the stabilizer. You can drain about a quarter of the water and add fresh water again to break the chlorine lock.

This will make your hot tub a little refreshed. However, if the situation is too bad, partially draining it once will not work. You might need to do it a few times to completely fix the problem. Make sure to check the chlorine level each time before draining refilling.

Non-Chlorine Shock

Non-chlorine shock is a powerful oxidizing agent which has no odor. its main work is to remove toxins from the water giving you a relaxing and hygienic hot tub experience.

The non-chlorine shock will oxidize the chlorine, making it useful again to kill bacteria. It restores the chemical balance in the water and makes it cleaner as well.

There is a formula to know how much you need to add to the water. And it is -

Non Chlorine Shock = (Total chlorine - free chlorine) X (Amount of water in your pool in gallons)/10,000) X 2

Using this formula you can easily determine the amount of non-chlorine shock needed in your pool to neutralize those free chlorines.

Chlorine Shock

In this method a generous amount of chlorine is added to the water. This spikes the chemical levels in the hot tub, allowing chlorine to break the chemical bond of the chloramines.

To fix a chlorine lock, a chlorination breakpoint needs to be done and a large chlorine shock helps achieve that. However, before you add shock to the water in your hot tub you need to make sure that the PH balance is correct.

How Much Shock Do You Need To Break A Chlorine Lock?

The amount of shock you need to use depends on the type of shock you're using. You will need to know the chlorine level in the water, free chlorine, and how many gallons of water is there in your pool.

If you want to increase the level of chlorine in the hot tub than half a bag of shock per 10,000 gallons is ideal to do that. If there is a large number of chloramines in water then a high level of shock is necessary to oxidize the water. A chlorine level between 10 ppm and 30 ppm preserved in the water is perfect to kill any bacteria.

It is necessary to reach the breakpoint each time you shock your hot tub. If you cannot achieve the breakpoint then there can be even more chloramines in the water. If this continues to happen, you may have to fully drain the water to fix this issue. Thus, you need to make sure you're using the correct amount of shock and checking each time after shocking your hot tub.

Is It Safe To Stay In The Hot Tub With Chlorine Lock?

Chlorine levels between 5 ppm-10 ppm in the hot tub are safe enough for you to soak in. According to some experts, chlorine lock is not a real issue. However, the water does become unhygienic as the chlorine becomes ineffective. With no sanitizer in the water, bacteria grow every minute making it unsafe for you and others using the hot tub.

In the water, chlorine breaks down into chemicals that kill bacteria. The water in the hot tub needs to be sanitized as it is not possible to drain the hot tub every time someone enters. It also needs to remain clean and chlorine helps to do that. You don't know what kind of bacteria someone brings with them to the water and so it is unsafe. Thus, a residual cleansing is vital.

The safety of using a hot tub with a chlorine lock depends on the environment. If you’re using a public hot tub then it is advised not to stay in it for a long time with a chlorine lock. This is because a lot of people enter the hot tub and you don’t; know the kinds of germs they’re bringing with them! A private hot tub is still safe to use but it is still best not to continuously.

How To Check Free Chlorine Levels?

Pool test kits usually don’t indicate free chlorine levels. Some do and some don’t. So, if yours don’t then you can just buy free-chlorine level test strip. Now how to use it properly?

Take a vial or cup full of your hot tub water. Make sure it is at room temperature. If it’s an especially hot day, bring it inside the house and leave it for an hour or more.

Next, take out a strip from the testing kit and dip it into the water sample. Gently move it back and forth inside the water for at least 5 seconds. You will see that the strips have changed color.

Now, your kit should come with a color chart. Or there should be a color chart at the back of the strip container or packaging. Compare the color you got on your strip to the chart that came with the box. That should give you an idea of the amount of free chlorine in your hot tub.

The darker the shade is the worser your chlorine lock problem is. And if it’s really bad the best course of action would be to call a professional and let him deal with the problem at hand.

Beware of Expired Testing Kits

It is important to have a proper chemical balance in the water so you can enjoy it safely while in the hot tub. Testing kits are the perfect way to measure this balance but sometimes, they can be expired causing them to give incorrect readings.

Most of the pool testing kits last a year, two at maximum. The expiration date is labeled on the packaging of the testing kit and is vital to avoid using chemicals past their date of usage. These chemicals can then give false readings if they are expired. So, it is always wise to check the expiration date of any testing kit before use.

A faulty or expired testing kit may be the reason why you are not getting the chlorine levels you are expecting. That is always something to consider before heading onto more serious measures. 

Now, if you don't want your testing kit to expire quickly then you need a good place to store it in. you will need to put it in a proper tube and seal it so that it doesn't get contaminated. This will make sure that they last at least two years. You should also store them in a cool and dry place. That will ensure the chemical stays active for a long time.

Now that you know why the chlorine in your hot tub disappears, keeping the chemical levels in your hot tub balanced is a very important task. Chlorine lock is not a very harmful issue but if it goes out of control, it can be dangerous for you. You have to pay attention to the signs and find a solution to fix them as soon as possible.

Also, do consider personal faults or test kit issues before jumping into any conclusions. Thanks for reading the whole article. I hope you can fix the issue you’re facing and enjoy your hot tub safely again!

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Written by Ferdi Vol
Ferdi Vol is a pool and hot tub owner who has been working in this industry for over 5 years. He has learned all the ins and outs of maintaining pools and hot tubs, as well as how to privately own one. Ferdi Vol is also passionate about blogging, researching topics that he shares with his readers online via this blog.
About Ferdi Vol
About Pool Uncle
Pool Uncle is a blog that focuses on helping pool and hot tub owners get the right tools, maintain their pools and hot tubs, and learn about how to care for them. It provides readers with all of the information they need to keep their pools clean, safe, and looking great. The website also publishes original articles about pool maintenance topics such as filtration systems or algae prevention techniques.
About the Author
Ferdi Vol has been in the swimming pool and hot tub as an owner for over 5 years. His experience ranges from owning a pools and hot tubs and maintaining them. He’s learned about pumps, filters, chemicals, cleaning products, treatment systems… you name it!
About Ferdi Vol
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