keeping chlorine level in swimming pool

Letting the chlorine level in your swimming pool drift down to zero can have serious consequences.  During a previous mid-summer pool season, I had added more chlorine tablets to my chlorinator.  When I do this, I turn the chlorinator off so water does not rise up and out when adding more tablets.  Well, I forgot to turn the chlorinator back on, and several days passed.  I did not give it much thought, as I had added plenty of chlorine and the water was balanced, so I thought things should be able to run fine for a few days on its own, right?

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Well, I opened the pool cover, and the water looked as though I had dumped a few (dozen?) gallons of milk into the water.  I could not see the bottom of the pool, and the water had a whitish tint that made me realize something was obviously wrong.  We did a quick test of the chlorine, and there was none in the water.

We then spent the next two weeks trying to get the water balanced as we shocked the pool twice, only to then fight water balance issues of low pH, low total alkalinity, and high calcium hardness.  What a pain.  I lost time and money buying and adding chemicals, plus draining a portion of the pool water.

This all likely could have been prevented if I had simply watched the chlorine level more carefully.

In this article, I explain why it is important to monitor and adjust the chlorine level in your pool when needed, what general steps are needed to maintain your pool water chlorine level, and I offer a few tips to keep your pool optimally chlorinated.

You can also make sure you know how to test your swimming pool chlorine level, and also know what to do if the level is off; raising swimming pool chlorine if the level is too low, and lowering swimming pool chlorine if the level is too high.

Importance for your pool

Why maintaining swimming pool is important

Chlorine is the most widely used substance to sanitize swimming pool water.  There are other chemicals, devices, and sanitizing systems, but if your pool is chlorinated, then keeping a proper chlorine level in your pool is vital to keeping you water clean and healthy for swimmers.  You can also avoid costly extra maintenance that can happen if the chlorine level is not maintained.

The recommended range for chlorine in residential pools is 1 – 3 ppm (parts-per-million), but you should really keep the chlorine level at 2 – 3 ppm.  Commercial pools should run their chlorine levels at 3 -5 ppm as their bather load is usually much higher.  Anything between 5-10 ppm is still safe to swim, but you are risking damage to equipment and certainly complaints from swimmers.  Some experts recommend no swimming unless the chlorine is 8 ppm or less.

You need to make sure your water is first balanced before expecting an effective sanitizing program using chlorine.  If you water is unbalanced, much more chlorine needs to be added to the pool water to achieve the same effect and the chlorine that is able to perform sanitation duties often is effective for a shorter amount of time.

If your chlorine always seems to be low, even though you are adding what seems like excessive amounts of chlorine, this can be caused by:

  • Excessive organic contaminates or algae present in the water, causing high chlorine demand.
  • A depleted or malfunctioning sanitizing system like an ionizer, ozone generator, or mineral sanitizer.

If your chlorine is high, this can be caused by several things:

If your pool chlorine level is too low (less than 1 ppm).

  • Unsanitary pool water.Harmful bacteria, algae, and other microbes can quickly multiply in water lacking enough sanitizing ability.
  • Cloudy pool water.As contaminates enter your pool, the lack of chlorine in the water prevents the water from being able to oxidize these contaminates
  • Difficulty keeping water balanced.  In trying to restore the chlorine level in the pool water, such as applying a shock treatment, adding chemicals can force water balance levels high or low, such as pH, total alkalinity, and calcium hardness.

If your pool chlorine level is too high (greater than 3-5 ppm).

  • Corrosive water.Highly chlorinated pools tend to have low pH.  This acidic pool water can damage pool surfaces and equipment.  Corroding metal surfaces and pool walls and floors.
  • Complaints from swimmers.Excessive chlorine will sting eyes, nasal passages, and dry out skin. All these make for an uncomfortable swimming experience.
  • Added expense.Adding unneeded chlorine is a waste of your time and money.
  • Faded clothing.

How often do you test chlorine?  You should test the chlorine ideally every day, certainly every day you use the pool, and always before and after large gatherings.  Even with devices like chlorinators that are designed to inject constant amounts of chlorine into the pool water, enough factors can cause the level to change day-to-day.

How to Maintain Swimming Pool Chlorine

The chlorine level in your pool is arguably the most important thing to maintain for a pool owner, as the chlorine level can change quickly and drastically, and you risk problems if the chlorine level is allowed to drift too high or low.

First make sure your water is balanced

You need to make sure you have balanced water in your swimming pool before expecting to get a good sanitizing ability from chlorine added to your pool.  The pH, total alkalinity, and calcium hardness all need to be within their ideal ranges.  Once your water is balanced, you do not need to test all levels as often, with the exception of pH, which should be tested every couple days during your peak pool season or after adding any chemicals.

Test the chlorine level

Once you have balanced your pool water and tested each level, you need to test the chlorine level.  I explain how to test chlorine in the following article:

If you are a pool owner and you do your own water testing, you are best off trying to set a testing schedule.  Every other evening, or every day prior to swimming; something that will trigger your into remembering to test.  Whether you use test strips, a test kit, or an electronic chlorine tester, the key is to test consistently.

Adjust the chlorine level, if needed.

If you discover your chlorine level is a little high or low, then you need to adjust this value.  In my opinion, it is much better to be slightly on the high side of the 1-3 ppm range.  If my chlorine level is in the 3-4 ppm area, I simply turn my chlorinator down a little and check the level again the next day.  I usually find the level has dropped to a number I feel comfortable with.  If the level is excessively high, I leave the pool cover off for a few hours on a sunny day, which will drop the chlorine level down quickly.

If I find my chlorine level too low, I also often see combined chlorine show up quickly, such as total chlorine at 1.0 ppm, and free chlorine at 0.5 ppm.  This results in a round of shocking the pool water.  Most often things like this happen at the peak of summer, with the water heated by the sun every day and peak pool use.  We also have windy days with plenty of dirt and debris getting into the water, creating high chlorine demand.

Do you need to raise or lower your chlorine level?  I have written guides for each:

Adding chlorine by hand and directly to your pool is time consuming, so i recommend installing a chlorinator or chlorine feeder, or at least placing a chlorine floater in the pool water.  These devices can save significant time, as they can deliver constant amounts of chlorine in the pool.

Pool Chlorine Tips

  • Do not wear nice, dark clothes while working with chlorine or bags of shock.  Chlorine in any form is notorious for  putting bleach spots on clothes.  If you store chlorine tablets, keep them covered and away from kids, pets, and any space where people are living.  I keep mine in a plastic bag and then enclosed in a 5-gallon bucket with locking top…and i can still smell the tablets.
  • Use gloves when handling the chlorine.  The chlorine dust will sting if you get it on your hands and arms if you have any moisture on your skin.  I often dip both arms in the pool after handling chlorine to eliminate any potential powder picked up while handling.
  • Don’t place chlorine tablets into your skimmer basket, especially if your pool is set on a timer.  The chlorine tablets will dissolve even when the water is not running, causing extremely high chlorine levels in your skimmer area.  When the timer turns the pool pump back on, this hyper-chlorinated water passes through all the equipment, and can corrode metal surfaces over time.
  • I recommend installing a chlorinator, as the chlorine is fed into the outgoing water as it leaves the main filter and back to the pool.  This way any high concentrations of chlorine are fed into the pool instead of the pool equipment.

Conclusion

The best thing you can do to successfully maintain your swimming pool chlorine level is to test the water chlorine often and consistently.  Maintaining chlorine levels is less costly in terms of money and time, as trying to restore the sanitizing ability of the pool water and keeping the water balanced is much harder to do if the chlorine level is too low or too high.

Occasionally get a second opinion; someone else do the test,  use a different method, or take a sample to your local pool service provider.  If you notice your chlorine level is too low or to high, try to correct this as soon as possible to avoid more trouble.

Source:

  • “Pool & Spa Water Chemistry, A Testing and Treatment Guide, Waterproof Edition, 2005. Taylor”