How To Lower Chlorine In Pool

How To Lower Chlorine In Pool

Water balance is critical to proper pool operation. At a minimum, the water must be sanitary and free of contaminants.

When people swim they are likely to produce skin oils that fall into the pool where algae feed on it.

Algae blooms can occur within days if not weekly depending on how high chlorine levels are maintained.

Chlorine also combines with urine metabolites to create chloramines which are not as effective at killing bacteria as chlorine alone.

The result is green or yellow pool water streaks plus stinging nasal passages, burning eyes, and irritated skin. You may have these problems even when your pool looks clean.

How to Tell if Your Pool Has Too Much Chlorine

It might be surprising to learn that it is possible for your pool to have too much chlorine.

Although it seems like the high levels of chlorine would kill off algae, bacteria, and other contaminants -so they wouldn't grow- this isn't always true.

Chemical tests are required to tell whether your pool is chlorinated but here are some ways to tell whether your pool has too much chlorine:

Any chemical test will immediately show if your pool is under-chlorinated, chemically balanced, or over-chlorinated - however not all these values are as serious as they may seem.

If the water smells so strongly of chlorine it almost burns your eyes and nose then there's likely too much in the pool.

After heavy rainstorms when water flows into the pool from the street there might be so many contaminants present that even with proper levels of chlorine algae begin to grow within hours.

Even after a thorough clean up you're advised to shock treat with chlorine and then brush and vacuum the entire pool several times before adding any algaecide products.

Testing Pool Water For Chlorine

Before testing pool water for chlorine always add the reagent to the bucket first and then add pool water. The results of this test tell you what is in your pool right now and can help you determine if there's too much or too little of it.

The Cl2 test measures free available chlorine; Clorox, calcium hypochlorite, or any granular product that releases chlorine into the water when dissolved. The result should be between 1 and 3 ppm (parts per million).

Anything higher than 3 ppm indicates excessive levels of chlorine in your pool - not unusual after rainstorms but normally undesirable for proper sanitizing purposes.

Any chlorinator system such as a salt system, mineral purifier, or ionizer will produce oxidation as a by-product as will the sunlight as it strikes organic substances in the water.

  1. You can determine whether there's too much or too little chlorine in your pool by testing for pH first and then chlorine levels.  (Related: How to Raise PH in Pool and How To Lower pH in Pool?)
  2. Next add a small amount of a product that uses chlorine such as Liquid Shock, which is an alkalinity increaser. Add 10 more ppm then test again. If the level has dropped below 3 ppm that's good but if not add another 5 ppm of shock and test again until you achieve results at 3 ppm.
  3. Now add a phosphate remover to remove all dissolved organics from the pool (you can use PhosFree).
  4. This time you'll test for Free Chlorine with the same reagent. You should find that it is between 0 and 1 ppm which means your pool water is balanced, chemically sound, and ready to swim in.

What If Your Pool Water Tests All Right But Still Has a Strong Chemical Smell?

If chlorine levels are acceptable but there's still a strong smell of chemicals check again for chloramines.

Since this isn't a chemical being added into the water there won't be any testing you can do to determine whether they're present.

The only way to know for certain is if people complain about eye irritation or skin stinging - even after heavy rains when everything else seems to be in order.

If you suspect that chloramines are responsible for the chemical smell there's only one way to deal with it.

Shock treat using 16 ounces (1 Lb.) of granular chlorine (not tablets) or 3/4 cup Liquid Pool Shock per 10,000 gallons of water.

Test for free chlorine again and if it's too high add 5 ppm more and test for a second time until you achieve acceptable levels.

If the smell isn't gone after this treatment -as might happen if people have been walking around in wet shoes- then chances are algae is growing inside the pool filter system.

To avoid any problems like this check your pool chemistry twice daily and never allow it to fall below 1 ppm of free available chlorine. If chloramines are present shock treat immediately and test for free chlorine levels again.

How You Can Reduce The Amount of Chlorine in Your Pool?

Since chlorine is the only effective sanitizer you can use, if your aim is to reduce its level in the water you must either close down the pool or switch to an alternative system that uses none at all such as ultraviolet sterilization or ozone.

Whether this can be achieved depends on many different factors including whether people have been walking around wearing rubber-soled shoes indoors after a heavy rainstorm or even going into their own bathrooms with wet feet.

There's nothing much you can do about chloramines once they're formed but a regular maintenance program will help prevent any build-up by keeping the water balanced, clean, and fresh.

Tips on How to Reduce Chlorine Use:

  1. The first step is to look at your pool chemistry. If you find that chlorine levels are high or if chloramines are present shock treat with 16 ounces of granular chlorine or 3/4 cup Liquid Pool Shock per 10,000 gallons of water. Test for free chlorine again and if it's too high add 5 ppm more and test for a second time until you achieve acceptable levels.
  2. Keep a closer eye on pool chemistry by testing twice daily before anyone enters the pool then after they have been swimming.
  3. Also, keep an eye out for any problems with algae growth in filters though this can be dealt with easily using a Filter Cleaner.

What If Chlorine Levels are Low?

If your free chlorine levels are low you need to shock treat the pool otherwise there may be health hazards for swimmers at worst or green algae growth at best.

To do this use 16 ounces of granular chlorine (not tablets) or 3/4 cup Liquid Pool Shock per 10,000 gallons of water depending on which type of shock is available.

Test again after 24 hours and if the level has dropped add another 5 ppm and test again until you achieve results at 3 ppm.

If the free chlorine level drops below 3 ppm it's time to close down until you can raise it to this safe level again.

If that isn't possible then switch over to an alternative system such as Ultraviolet Sterilisation or Ozone.

Follow these simple pool water chemistry rules when shocked treating your pool and always remember when in doubt, treat!

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Jeff L.

Jeff has been an avid swimmer as long as he can remember, with his first swim lessons in Kindergarten in the 1980s, and became obsessed with pools and swimming shortly thereafter.