Recently, I spoke with a commercial pool owner. He told me that he had a purple color on the walls of his pool. With just a couple of questions, I could determine the problem. I also suggested a simple way to remove the color from the pool. However, the basis for the problem was a bit different- it’s back to the basics of water chemistry to find a viable long-term solution to the problem.
The situation is the same with skin irritation in pools and spas. If you want to reduce the skin irritation symptoms, I’m sure there are a wide variety of lotions and oils readily available for your skin. However, if you want to look into the actual cause, we need to go back to the basics of water chemistry.

Many courses and hundreds of books are available (check with NSPF at www.nspf.org). So this will be a brief look into the most common causes of skin irritation caused by water quality-and solutions.
In this simplified view, there are probably four likely primary causes for skin irritation:1) Chlorine/bromine related.2) pH related.3) Bacterial rashes.4) Overuse.

First, let’s look at chlorine. Then, we will look at other water quality factors that may also contribute to skin irritation.
Often I hear people describe that they have a rash. They have been to the doctor, who told them they are allergic to chlorine. Although I am sure this condition does exist, it does not make sense in about 99% of the cases– -maybe 99.9%. If this person has concluded that they are allergic to chlorine, how can they take a shower or wash their hands or, heaven forbid, drink water with chlorine?

Chemically, the active chlorine in swimming pool water is the same chemical as the chlorine in drinking water. Depending on the pool, the community, and other factors, I have seen many cases where there is less total chlorine in a commercial pool than in the municipal water system. But, wait! I do understand that the opposite is very, very true. There are many well-maintained municipal water systems compared to poorly maintained swimming pools, and the opposite is true.

So, what is important here? The first step to determining the source of the rash is to assess the quality of the swimming pool and spa water. The recommended ranges may vary a little from one area or state to another, but generally, the recommended Free Available Chlorine level should be about 1-5ppm. Many pools operate very effectively at levels around one ppm. Many factors must be considered to determine the optimal range for a specific application.
Most importantly, I suggested a Free Available Chlorine (FAC).

What is Free Available Chlorine?
When you dissolve any source of chlorine in clean (let us go to the extreme-distilled/purified) water, you get Free Available Chlorine. Free Available Chlorine is what kills bacteria, viruses, algae, etc. FAC is very effective for killing and oxidizing many organics in the water. Unfortunately, when the first munchkins jump into the water, sweat, body oils, and other organics combine with that good Free Available Chlorine and create Combined Chlorine or Chloramines.

The problem with Choramines is that they don’t kill nearly as quickly and effectively and cause irritation. As little as .2 ppm of Chloramines can cause eye and sinus irritation! When I go swimming without goggles, and my eyes are irritated as soon as I swim a length of the pool- – most of the time, the problem is Chloramines in the water. Unfortunately, the average person says,” too much chlorine!” But the reality is that there may not be enough Free Available Chlorine to keep the pool sanitary-although the pool smells like “chlorine.”
It is also true that several other things can cause that eye irritation–but generally, when the irritation is that immediate, it is most likely a high level of Chloramines.
You could have irritation from excessive chlorine– including Free Chlorine levels–, but generally, those levels would be as high as 10ppm or more. Most people will not notice a problem in 10ppm – as long as the other water quality factors are within the proper range.

Free Available Chlorine plus Combined Chlorine equals Total Chlorine. Therefore, you must be able to test for 2 of the three factors to maintain the pool or spa properly. Most health departments require testing with a DPD test kit. You may have an automated system that measures the sanitizer’s effectiveness with electronic probes, but even then, the system needs checking for accuracy with a DPD test kit. The DPD test kits turn the test water shades pink or purple to determine the amount of chlorine in the water. Each kit is a little different, but you generally use one test solution to test for Free Available Chlorine and another to find either the Chloramine or the Total Chlorine level. Remember – Free plus Chloramines equals Total.

So, the Free and the Total readings should be the same. If they are not the same, then you have Chloramines- bad chloramines!
However, another related issue is testing the chlorine level if you suspect an extremely high one. The DPD test will bleach out in this situation, giving you a zero or low reading when the chlorine level goes over 12 ppm.
If you suspect that problem, 1) dilute the test water with distilled water and retest or 2) use an OTO test kit. This test kit is not generally approved for commercial applications because it does not give you a free chlorine reading–only a total chlorine reading. However, OTO will not bleach out– it turns darker yellow than brownish red, etc… If you get a bright yellow or brown reading with OTO, your chlorine level is well beyond 10ppm.

Ok, so what do we do about this?

First, you have to test the water properly. If there are zero chloramines (remember, just .2 ppm will cause eye & sinus irritation- and could cause skin irritation in the right situation), then we go to the next concern- -pH. If chloramines are present, then we need to get rid of them!

How do we get rid of chloramines?

Although you will need to finish testing the water for other factors, we will discuss those factors in another article. It is impossible to treat the water properly if we don’t know all the factors- as the different water quality factors affect each other. Assuming that the water is properly balanced-except for those pesky chloramines, we need to oxidize the chloramines. There are many ways to do this. Many commercial pools today will have an ozone generator or a medium pressure UV unit that will reduce chloramine levels if it works properly. If not, we return to the old standard– we shock the pool. This is where most people get confused. If you smell lots of chlorine in the pool area (because there are lots of smelly chloramines), why would you want to add MORE chlorine? The problem is the oxidation of chloramines. If you add the correct amount of chlorine to the pool within hours, the smell will be less because you have oxidized those nasty chloramines.

The rule of thumb is that for every one ppm of chloramines in 10,000 gallons of water, you add 10ppm of free chlorine. It depends on the type of chlorine you use to determine the dose. But for example, for a 10,000-gallon pool with one ppm of chloramines, I would add 1 pound of Calcium hypochlorite or 1 gallon of swimming pool bleach (sodium hypochlorite).
This raises the chlorine level temporarily, so you generally do NOT do this while swimmers are in the water. The best time is in the evening after the pool is closed.

Alternatives (Ozone & UV) were listed above, plus there are non-chlorine shock treatments that do not raise the chlorine level, but they will oxidize the chloramines and allow swimmers to re-enter the pool after 15 minutes. However, these treatments are a bit more expensive, and if you use an automated sensor system (ORP), they will reduce the ORP reading accuracy for a while. They will also give a false high DPD total chlorine reading for several hours.
We have reviewed much of the basics about proper chlorination for your swimming pool and how to avoid skin irritation due to improper chlorination.

I know it’s illogical, but let’s jump to #4, Overuse, to gain a bit of perspective. Although eye irritation that you notice immediately is most often due to chloramines, if your kids come home with red eyes after spending the day at the pool– it is quite possible that the water is well balanced. Likewise, if you stand with your eyes open under the shower for a couple of hours, your eyes will also hurt. But it’s an overuse issue– you are washing all of the natural moisture away from the eye, irritating regardless of the water quality. So, to diagnose the problem, we need more information than just that someone has red eyes or skin irritation.
Whew– that is probably more water chemistry than most of us want to digest in one sitting- -so we will address the other factors.

About the author. J Kevin Tucker
I have worked in and around swimming pools for the past 40 years.
Like many people in the industry, I started lifeguarding, coaching, and teaching swimming lessons. I ran, operated, maintained, and programmed pools – primarily large, heavily used pools- for over 15 years. For the last commercial pool that I ran, I grew the programs from summer enrollment of about 200 to a summer enrollment of about 1900 in 5 years. I was certified and taught everything from infants to scuba. I trained hundreds of instructors. In addition, I have taught aquatic exercise classes (in the late 70s and early 80s) and have conducted aquatics classes for people with disabilities.
I worked for BioLab, one of the largest swimming pool chemical manufacturers, for ten years, providing sales, troubleshooting, and training for distributors, dealers, and consumers in the US west of Ohio for residential and commercial applications.
In 2006, I was introduced to the H2OGym product line of aquatic exercise equipment by a friend that had worked for a competing chemical company when I worked for BioLab. I now import from Taiwan and market the underwater treadmills, steppers, and other equipment for sale primarily in the US. My company is H2OGym-US, LLC.