Our APi tech department gets several calls asking about CHLORINE LOCK, what the heck is it? And how do I fix it? Usually, chlorine lock is caused by one of two things. One being a stabilizer level of over 100ppm, and the other being a high combined chlorine level (over 1ppm), causing a strong chlorine smell, and possibly green or cloudy water that doesn’t change after shocking. As we have discussed in earlier RICK’s REMEDIES, stabilizer is the suntan lotion for your chlorine that protects your chlorine from UV rays and is a necessary component of balance. Unfortunately, many things you add to your pool contain high levels of stabilizer, and you are often unknowingly raising the stabilizer level too high, causing over stabilization, or CHLORINE LOCK. The main culprits are Trichlor tablets or Dichlor granules. Trichlor may be as much as 40% stabilizer! And DiChlor follows closely behind.



Unfortunately, the most economical way to reduce stabilizer is to drain off water! You may have to drain off as much as 1/3 of your pool water to get the level below 55ppm. This will take the handcuffs off of your chlorine and let it get back to work.


If your stabilizer is under 55ppm you don’t have a chlorine lock, you just have high combined chlorine. If this is the case (which it often is!) you need to shock your pool and reach break point chlorination to remove the smelly combined chlorine. As we discussed earlier in RICK’s REMEDIES break point is achieved by super chlorinating the pool to 10 times the calculated combined chlorine. Remember TC-FC=CC.

Here is an example! Using the formula above we calculate a combined chlorine of 5ppm. If your pool is 10,000 gallons. To remove the combined chlorine, you must reach 50ppm of chlorine for a short period of time. 49ppm will not work and will make the problem worse, so always error on the high side!

So, what are your options to reach 50ppm of chlorine in 10k gallons?

5# 73% calcium hypochlorite

10# dichlor (remember this will also raise stabilizer)

5 gallons of liquid pool shock

Each of these options will reach breakpoint!


Another alternative is to use a non-chlorine shock! These products will remove combined chlorine without reaching breakpoint. Although there is no rule of thumb, you can apply and test repeatedly until you reach the desired reading of combined chlorine of less than 1 ppm.

Ricks Rule Of thumb:

Did you know EZ-POOL, PEPPER! And EZ SPA all contain Non chlorine Shock?

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    – Donna, Ohio
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    – Trish, Greensboro, NC
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