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To Stabilize or Not?



To stabilize or not?  We get this question all the time from clients!  Here are a couple facts and recommendations when using stabilizer in your pool.

  • In a pool environment, "stabilizer" is the same thing as "conditioner" is the same thing as "cyanuric acid".  Different words for the same product.  
  • Stabilizer is 99.9% of the time an OPTIONAL product.  You do not have to add this product to your pool.  It does not help balance your water in any way, and it does not help your sanitizer (chlorine) work any better.  Completely optional.  
  • Stabilizer does not come into your pool via your makeup source water.  It is only there if you add it.  
  • Stabilizer (or stabilized chlorine like Trichlor or Dichlor) should ONLY be used with outdoor pools.  There is no reason to use stabilizer for an indoor pool, and in fact most health codes prohibit it. 
  • The sun's UV rays kill chlorine.  Simplified, stabilizer is "sunscreen for your chlorine".  The addition of stabilizer to your pool protects your chlorine from the UV rays of the sun and makes your chlorine residual last longer.  
  • The use of stabilizer is almost always a financial decision.  It saves money because you are not losing all that chlorine to the UV and having to frequently replace it.
  • What a great product right?  Why not keep a ton a stabilizer in your pool all the time?  Well, like all things in life, there are drawbacks to using stabilizer.  Specifically, stabilizer protects your chlorine, BUT (and this is a BIG BUT) ... it also locks up your free chlorine and prevents (or slows) it from disinfecting all those nasty "bugs" that it is designed to kill.  The more stabilizer you add to your pool, the "sleepier" your chlorine gets.  
  • The National Swimming Pool Foundation (NSPF) recommends 30-50 ppm of stabilizer.  Theoretically, this is the amount of stabilizer that will provide the ideal "sweet spot" and perfect balance of saving money but still having ample free available chlorine to kill those nasty bugs in your water.  There is evidence however that even as little as 10 ppm of stabilizer can make a tremendous impact in reducing UV destruction of chlorine.
  • Most health codes have maximum stabilizer levels spelled out pretty clearly... often times up to 80 ppm or even 100 ppm (which in our opinion is a little too high and even potentially dangerous).  We recommend 30-50 ppm, or even less if you can measure it that low. 
  • Common question: Can't I just add a "stabilizer down" product when I need to lower my stabilizer?  Answer: No.  This product does not exist.  The only way to reduce the stabilizer level in your pool is to drain water and replace with fresh water.  And even then, stabilizer can soak into pool shells, pool equipment, filter media, etc.  You can drain your entire pool, refill it, and you will still most likely have small amounts of stabilizer present in your pool.
  • There is research available that suggests that to ensure you still have adequate killing power in your stabilized pool, your free available chlorine (FAC) should be at least 7.5% of your stabilizer level.  Therefore, if you had a stabilizer level of 50, you should be keeping at least 3.75 ppm of FAC, or at 100 ppm of stabilizer, you should have 7.5 ppm of FAC.   
  • Recall the trichlor and dichlor mentioned in bullet #4 above?  Lets dig into that a little more...
    • These two products include chlorine & stabilizer...all packaged and pressed together into a puck or stick or tab or granular.  So...every time you add a di/trichlor puck (or product) to your feeder, you are also adding stabilizer.  
    • Due to the bullet above effectively lose a lot of control over stabilizer levels when you use only trichlor or dichlor.  Why?  Because your hands are tied.  We know that you must continually add chlorine to keep up your sanitizer residual, but every time you feed chlorine you are also feeding stabilizer along with it.  If you need to use di/trichlor...we recommend you switch to a non-stabilized Cal Hypo chlorine product (or other) when your stabilizer reaches the desired level.
    • For pools on di/trichlor, it is not uncommon to see stabilizer levels way too high, well above 100.  Many clients with small pools receive violations for this.  If you consider that for every 10 ppm of trichlor you add to your pool, you are adding 6 ppm of stabilizer --  if your chlorine demand is 2 ppm, then every 10 days your stabilizer concentration is going up by 12 ppm.  This can quickly get out of control.  

So...if it were our pool, we would:

  1. ...consider not using stabilizer at all unless we were pressured by management or finances. And, only in an outdoor pool of course.  When used correctly, stabilizer is a very useful tool and is, understandably, especially helpful in hot sunny areas (read: Phoenix, Las Vegas, etc).  It just needs to be properly managed.  
  2. ...exercise extreme caution to ensure that our stabilizer levels stay around a 20-30 ppm level and we would NEVER let them go above 50 ppm.
  3. ...not use a di/trichlor product unless we had to.  And if we had to use a di/trichlor product for some reason, we would ensure that we tested the stabilizer level daily and would be prepared to immediately change to a "non-stabilized" chlorine-only sanitizer as soon as we hit our target stabilizer levels.
  4. ...reconsider our stabilizer level anytime there was a local crypto or other RWI outbreak.  Run that pool hot (chlorine, not temperature) with no stabilizer to ensure a quicker kill for those tough to kill RWI bugs. 
  5. ...ensure that we follow the ADDITIONAL hyper-chlorination steps that pertain to stabilized pools if we ever have a diarrhea situation in our pool.  The typical "raise the pool to 20 ppm for 12.75 hours at a pH of 7.5 or less" doesn't work if there is stabilizer in the pool.  See the amended CDC instructions here.

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