View Full Version : Pool Chemical Question for Pool Operators

February 23rd, 2006, 04:23 PM
My question involves the regulations and the short-term health effects of swimming in water that contains too much chlorine. The other night, our pool (indoors) measured as follows:

pH: 6.8 - 7.0
Chlorine: 10 ppm

My understanding is that the pH should be in the 7.2 - 7.8 range, and the chlorine should be in the range of 1 ppm - 3 ppm.

My questions are:

1. Is there a safe upper limit for chlorine in a pool?

2. If the pool tests above that limit, should it be closed?

3. What are the short-term health effects of swimming in water
chlorinated to 10 ppm?

Some brief research on my part so far has only shown that our county has an acceptable mininum level (1 ppm), but no guidelines on a maximum level.

February 23rd, 2006, 04:48 PM
High chlorine has never bothered me. But, the other day we had either very high or very low Ph (I can't remember). It was horrible. About 30 minutes into the workout and you got terrible dry mouth and a hacking cough. It was impossible to wash it off, made your hair feel like straw. That was sheer misery but we fought through the pain.

February 23rd, 2006, 04:57 PM
Originally posted by aquageek
That was sheer misery but we fought through the pain.

You are such an animal.

February 23rd, 2006, 05:10 PM
Oh, but I cried like a little baby when I got home in an (failed) attempt to get some quality Saturday couch time.

February 23rd, 2006, 05:52 PM
With these measurements:

pH: 6.8 - 7.0
Chlorine: 10 ppm

We experienced the following:

-- We all had that "cotton mouth" feeling in our mouths by the end of the workout.

-- The back of my throat burned.

-- One guy had to get out early because he was having breathing difficulty.

February 23rd, 2006, 06:17 PM
Those are the same symptoms we had. We were told it was due to the Ph being off, not the chlorine.

February 24th, 2006, 10:17 AM
The chlorine levels, pH, and total alkalinity all work together in the pool water, and water temperature also plays into it. The calcium hardness also impacts these.

The only way to get rid of high chlorine is to drain some water, other than just not adding any and waiting for it to go down.

How warm is the water? The warmer the water, the more chlorine needed.

In the summer months, I need to add chlorine to my backyard pool at least every week (sometimes 2x), especially when the water temp gets to 95 or higher. Of course now I may add every 2 weeks, since it is in the 60s, and I'm not using it.

Did you test the water yourself? I'm curious how you came up with the measurements. The kit I have is not 100% accurate; I go to a pool store with a water sample for the most accurate tests.

Rich Abrahams
February 24th, 2006, 11:58 AM
Anna Lea,

I've been a Certified Pool Operator Instructor for the past 22 years.

Your problem was not the chlorine. Although higher than normally desirable, it shouldn't cause the discomfort. It was the pH that was way out of line. Ideally, it should be between 7.4 and 7.6 for human comfort and appropriate water balance. However, you certainly didn't have to worry about any pathogens in the water. Chlorine is is more than 3 times more effective as a sanitzer at a pH of 7.0 than at 8.0. Also, chlorine is effectively removed from the water by adding a chemical called sodium thiosulfate.


Anthony Thompson
February 24th, 2006, 01:11 PM
Aren't the water quality issue all connected ? High chlorine will create low pH as well may increase the creation of chloramine & chlorine vapors hanging over the water of the pool. I'm sure the low pH create some basic discomfort to peoples skin, hair and inside swimmers mouths, but the vapors seem to be more of a health concern especially for people with asmtha, heart conditions, and other pre-exisiting medical issues.

The regulation and enforcement water quality (chlorine, pH, alkininity, etc) as well as air quality in aquatic facilities seem to vary dramatically from state-to-state, and county-by-county in the states without regulations. I'm sure swimmers are reluctant to report their own facilities to the health department, and they all are probably understaffed.

Seem like a good issue for USMS Health/Safety/Sport Medicine Committe to investigate !

Anthony Thompson

Rich Abrahams
February 24th, 2006, 04:02 PM

Chlorine's effect on ph will vary depending on the type of chlorine used. The most common chlorine compounds used these days are calcium hypochlorite and sodium hypochlorite. These both raise pH and other chemicals must be added to lower the pH levels. Gas chlorine (not commonly used anymore) will lower pH. Two forms of stabilized chlorine will lower pH bet should never be used in an indoor pool.

It is true that high levels of chlorine can be a problem if the water is heavily agitated (big kick sets) or air circulation is particularly pool.

With a pH of below 7 and chlorine levels at 10 I would be really surprised if there was a chloromine problem. That is usually associated with low free chlorine, high pH and heavy organic loads.


Peter Cruise
February 24th, 2006, 04:16 PM
Sounds like the pool chemistry in North Carolina could lead to serious mutations & brain damage, which would explain a lot...

February 24th, 2006, 04:17 PM
I'm gonna get you one of these days, Cruise.