How To Fix A Chlorine Lock

Chlorine Lock

A Chlorine Lock occurs when your Total Chlorine is Higher than your Free Chlorine, resulting in High Combine Chlorine. This usually happens when water is not properly shocked weekly, and when the proper sanitation residual isn’t consistent.


There are three types of Chlorine to test for, that not all at home test strips or kits accurately test.


Free Chlorine is the chlorine that sanitizes.


Total Chlorine is all the chlorine in the water – even the chlorine that’s wrapped up in organic or inorganic materials.


Combined Chlorine is the Total Chlorine minus the Free Chlorine. The difference is all the organic and inorganic chloramines. Combined Chlorine should ideally be at zero. Total Chlorine and Free Chlorine should be equal to each other.


In order to get rid of a Chlorine Lock, you must achieve Breakpoint Chlorination. To achieve Breakpoint, the Free Chlorine in the water must be raised to about ten times the amount of Combined Chlorine. If not enough Free Chlorine is achieved, any Chlorine added goes straight to Combined. Also, if you add too much, the Chloramines may evaporate, and then re-dissolve, making no change.

There are a few ways of ridding a lock, but the most effective way we have noticed is through dilution, in part with oxidizing, and super chlorinating. Also, this is the most cost effective. Sometimes Locks can be difficult to break, and can take a few attempts if using chemicals alone. We always recommend retesting 48 hours after super chlorinating, to allow Chlorine to burn off, and to avoid false readings.

The best way of preventing a Chlorine Lock, is by always keeping the recommended Chlorine residual of 2ppm – 5ppm, shocking once a week, and bringing in water tests regularly. Although it is good preventative maintenance to test on your own at home with your own kit, by getting it tested by a Certified Water Testing Professional at Viscount Pools of Metro Detroit, we catch important details that at home test kits or test strips will not. Plus, water testing is always free for our customers!

If you have any questions, or if you think you may have a chlorine lock, or any other water chemistry problem, visit our “Ask Wally Jr.” Page, and a staff member will get back to you as soon as possible!



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