The Best Way to Break Chlorine Lock

best way to break chlorine lock

If you are a pool owner, you may have heard of chlorine lock before.

There’s a lot of controversy about whether or not chlorine lock is real. Some people complain it’s the wrong term to use because they believe it doesn’t accurately depict what actually goes on inside the pool water. And others believe this term is just fine to use.

In this article, we’ll discuss this topic in detail, so you can make your own conclusion. 

What is chlorine lock?

So, is chlorine lock a real thing or just a myth?

Chlorine lock is believed to be a phenomenon that results from the presence of an excess amount of conditioner (cyanuric acid) in your swimming pool. Although a pool conditioner, in a moderate amount, helps chlorine work more effectively, it is counterproductive when present in high doses.

Instead of protecting chlorine from the sun like it’s supposed to, the excess conditioner in your pool essentially ‘locks up’ chlorine from doing its job as a sanitizer, making it unusable.

Some people argue that chlorine lock isn’t real, but they are missing the point. What’s important to understand is that a conditioner overload in a swimming pool causes chlorine to lose its effectiveness.

What are the signs of chlorine lock?

The signs of chlorine lock are not too different than if your pool didn’t have any chlorine. For example, if your pool starts to turn green and cloudy, it’s a likely sign of chlorine lock.

Another sign of chlorine lock is when your pool gives off a strong ‘chlorine’ smell. Many people wrongly believe the smell arises from chlorine. But in reality, it’s actually chloramines that produce the smell.

Chloramines are chemical compounds that are created from the reaction between chlorine sanitizers and ammonia. When this chemical builds up in your pool, it starts to impede free chlorine and slows down the sanitization process, resulting in the ‘chlorine lock.’

Yet another possible sign is if your test result fails to show a rise in chlorine level, despite adding chlorine sanitizers into your pool. In such a case, it can be an indication that pool conditioners are restraining chlorine molecules. 

One more thing to keep in mind is that you are increasing the risk of chlorine lock if your pool conditioner level starts to surpass 80 parts per million (ppm). So, it’s important to continually monitor your pool chemical to ensure the level doesn’t go out of hand.

Having said all that, the best way to determine if chlorine lock is present is to test the level of total and free chlorine in your pool. If the ratio of total and free chlorine is one-to-one, then your pool is in good condition. If the total chlorine level is significantly higher than the free chlorine level, it may be a sign of chlorine lock.

How to fix chlorine lock

Luckily, there are a few things you can do to improve the situation if your pool suffers from this.

Drain your pool partially

This is a tried and true method for getting your pool back to a balanced state. There are no chemical products that can reduce the level of your pool conditioner. So, the best way to clear your pool of a conditioner is to drain it.

I suggest you drain about one-third of your pool before you re-test the pool. You can repeat the process until your pool reaches an ideal conditioner level.

This is the most reliable way to restore the balance in your pool, although it can be time-consuming.

Shock your pool

This is another effective way to treat chlorine lock. Shocking your pool is synonymous with the hyper-chlorination of the pool. You are essentially adding chemicals to raise the free chlorine level in your pool.

More often than not, calcium hypochlorite is used for hyper-chlorination purposes since it’s one of the most powerful shocks available. It’s a white solid that comes in granular or tablet form. Not only does it shock a pool to raise the free chlorine level, but it is also an effective sanitizer on its own.

Before you go ahead with shocking your pool, make sure that your pool’s conditioner level hovers around a somewhat ideal range, which is approximately 50 ppm.

Also, I recommend you shock the pool when there’s no sun outside. The main reason for shocking your pool is to increase chlorine’s effectiveness, but exposure to the sun has the opposite effect. So, it makes most sense to avoid shocking your pool during the daytime.

Retest your pool water after you apply the shock and repeat the process if necessary.

Apply non-chlorine shock

Instead of applying chlorine-containing shock, you can use non-chlorine shock to treat chlorine lock.

Non-chlorine shock oxidizes the chlorine, helping your pool clear up and return to its balanced state.

Check out the image below to calculate the amount of non-chlorine shock you will need to apply to your pool. TC stands for total chlorine, and FC stands for free chlorine level.

non chlorine shock calculation


Whether chlorine lock is real or not, there’s a little doubt that overloading a pool conditioner causes problems to chlorine molecules in your pool.

It’s essential that you first correctly identify problems in your pool by accurately measuring your pool chemicals. This will help you determine what type of modification you need to make to re-establish your pool’s balance.

I wish you the best of luck!

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