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Maintaining the proper chlorine level is an important part of keeping swimming pool water sanitized, but understanding chlorine involves more than simply checking whether chlorine is present.
In this Sonco Pools & Spas water chemistry training video, we explain the difference between free available chlorine and chloramines, demonstrate how to test for both, and explain how those results can help determine when your swimming pool actually needs to be shocked.
For this training series, Sonco recommends maintaining approximately 1–3 parts per million (ppm) of free available chlorine, with approximately 3 ppm being the preferred target demonstrated in the video.
Free available chlorine is the fresh chlorine in your swimming pool that is ready to sanitize the water.
It doesn’t matter how that chlorine enters the pool. It may come from:
A chlorinator
Liquid chlorine
A salt cell generating chlorine
Free available chlorine is the chlorine that is ready to combat bacteria and algae.
This is the “good chlorine” we’re looking for when testing swimming pool water.
The video demonstrates the free-chlorine test using a Taylor test kit.
Using the reference chart, add five drops of R-001 reagent to the water sample.
When using drop reagents, Sonco recommends holding the bottle straight up and down. This helps produce a consistent droplet size.
Next, add five drops of R-002 reagent.
Cap the vial, mix the sample, and compare its color with the free-chlorine scale.
The water tested in the video produces a free available chlorine reading of approximately 3 ppm.
This is the ideal result Sonco is targeting.
The training explains that 1–3 ppm is effective at killing bacteria and algae, and Sonco recommends keeping the chlorine level around 3 ppm rather than maintaining unnecessarily high levels.
No.
Maintaining 5 or 10 ppm of chlorine all the time isn’t better simply because the chlorine level is higher.
Excessive chlorine can:
Affect swimmers’ eyes
Bleach swimsuits
Be hard on swimming pool equipment
Be hard on fiberglass swimming pools
Be hard on vinyl-liner swimming pools
For this reason, Sonco does not recommend keeping a swimming pool continuously over-chlorinated.
Saltwater swimming pools create their own chlorine using the salt system and chlorine generator.
Because generating additional chlorine is relatively easy, the training explains that some saltwater pool owners operate their chlorine output too high.
Sonco recommends targeting approximately 3 ppm of free chlorine rather than continually maintaining readings of 5 or 10 ppm.
If the swimming pool doesn’t contain enough chlorine, the water is no longer being properly sanitized.
The video explains that a pool beginning to turn for the worse will often progress through recognizable stages:
Hazy → Cloudy → Green
Low chlorine allows algae and other contaminants to gain ground in the swimming pool.
For that reason, a low chlorine reading should be addressed promptly.
If chlorine is moderately high, one of the simplest methods discussed in the training is to leave the swimming pool uncovered.
Sunlight quickly destroys chlorine. Over several days, the chlorine level will often decrease naturally.
You should also stop or reduce the source of additional chlorine. Depending on your system, that could mean:
Shutting off the chlorinator
Stopping the addition of liquid chlorine
Turning down or turning off the salt cell
The trainer describes chlorine above approximately 5 ppm and approaching 10 ppm as too high and advises against allowing children—or anyone else—to swim when chlorine is excessively high.
The video also discusses a product called ChemOut, which can quickly reduce chlorine when the level becomes extremely high.
Testing free chlorine is only part of understanding the chlorine in your water.
When free chlorine goes to work against bacteria, algae, and other contaminants, the training explains that it eventually becomes what is called a chloramine.
Sonco refers to this as the “bad chlorine.”
Free available chlorine is fresh and ready to sanitize. Chloramines are the used chlorine left after that battle.
According to the training, chloramines are only about one-tenth as effective.
The chloramine test builds directly on the free-chlorine test.
Don’t discard the water sample after measuring free chlorine.
Using the same sample, add five drops of R-003 reagent.
If chloramines are present, the sample becomes darker and the chlorine reading increases.
In the video, the initial free chlorine reading is:
3 ppm free chlorine
After adding the R-003 reagent, the reading increases to approximately:
5 ppm total/combined chlorine
The difference indicates the presence of approximately:
2 ppm chloramines
This additional test tells you something a basic free-chlorine test alone cannot: whether used chlorine is accumulating in the water.
The training explains shocking in a very specific way.
The purpose of shocking is to get rid of chloramines.
Rather than automatically shocking the swimming pool on a fixed schedule, testing for chloramines allows you to determine whether shocking is actually needed.
Two methods discussed in the video are:
Non-chlorine shock acts as an oxidizer and is used to remove combined chlorine or chloramines from the swimming pool.
Boosting the chlorine level can also eliminate chloramines.
When trying to remove chloramines, keep the swimming pool uncovered.
Do not leave a solar blanket or automatic pool cover over the water because the chloramines need to gas off. Keeping the pool covered can trap them.
Not necessarily.
Some pool owners shock weekly or every two weeks as preventative maintenance.
However, the training explains that testing for chloramines gives you a way to determine whether the swimming pool actually needs to be shocked.
If chloramines aren’t present and the chlorine is free and available, there may be no need to shock the pool simply because a certain number of days have passed.
When chlorine is low, the training recommends addressing it quickly.
Several methods are discussed.
Liquid chlorine can provide an almost immediate increase in the chlorine level.
For a saltwater pool, increasing the salt system’s chlorine-output percentage can raise chlorine, although the video explains that this process is slower.
A one-pound bag of shock is another way discussed for quickly boosting the chlorine level.
If alkalinity and pH are properly balanced and approximately 3 ppm of chlorine is present, the training explains that the swimming pool should not normally be experiencing algae blooms or cloudy water.
For professional swimming pool water testing or help understanding your chlorine and chloramine readings, contact Sonco Pools & Spas at 815-654-7665.
Free available chlorine is fresh chlorine that is ready to sanitize the swimming pool by combating bacteria and algae. It can come from a chlorinator, liquid chlorine, or a saltwater chlorine generator.
The training explains that 1–3 ppm of free chlorine is effective, with Sonco recommending approximately 3 ppm as the preferred target.
No. The training advises against continually over-chlorinating the swimming pool. Excessive chlorine can affect swimmers’ eyes, bleach swimsuits, and be hard on swimming pool equipment, fiberglass pools, and vinyl-liner pools.
Low chlorine can allow algae to develop and prevent the swimming pool from being properly sanitized. The video describes deteriorating water as often progressing from hazy to cloudy and eventually green.
Stop or reduce the source of additional chlorine and leave the swimming pool uncovered. Sunlight destroys chlorine and can allow the level to decrease over several days. The video also discusses ChemOut for situations where chlorine is extremely high.
The training describes chloramines as chlorine that has already gone to work against bacteria, algae, and contaminants. This used or combined chlorine is much less effective than free available chlorine.
According to the training, free available chlorine doesn’t have the strong odor commonly associated with pools. The familiar chlorine smell and eye irritation are associated with chloramines in the water.
After performing the free-chlorine test, keep the same water sample and add five drops of R-003 reagent. If the color becomes darker and the reading increases, chloramines are present. The difference between the free and combined reading indicates the amount of chloramines.
The training recommends testing for chloramines to determine when shocking is necessary. If chloramines are present, non-chlorine shock or increasing the chlorine level can be used to remove them. If no chloramines are present, routine shocking may not be necessary.
No. When shocking or otherwise removing chloramines, the swimming pool should remain uncovered. The training explains that chloramines gas off from the water, so a solar blanket or automatic pool cover can trap them.