Safe swimming with elevated chlorine

[DavidD]

pH: 7.5
FC: 3.0
CYA: 30
The following don't have a much smaller effect on HOCl:
Temp: 80ºF
TDS: 550
The following has no effect on HOCl:
CH: 300

Richard,

What effect, though small, does TDS have on HOCl? Would the fact that salt makes up the majority of TDS in a particular sample increase the negative effect? Go easy on my limited abilty to grasp basic chemistry .

Dave

[chem geek]

Richard,

What effect, though small, does TDS have on HOCl? Would the fact that salt makes up the majority of TDS in a particular sample increase the negative effect? Go easy on my limited abilty to grasp basic chemistry .

Dave

In the presence of even small amounts of Cyanuric Acid (CYA), TDS has almost no effect on HOCl. So the calculations for a salt (SWG) pool would be the same as for a regular non-salt pool.

In a pool with no CYA, then the HOCl concentration from a non-salt pool to a salt (SWG) pool is lowered by around 5.7% (independent of Total Free Chlorine (FC) level).

Stop reading at this point. The following is for those who might want a more technical explanation.

(The technical reason for the difference is that without CYA, the TDS affects something called "ionic strength" that affects the equilibrium between the neutral HOCl and the charged OCl-. With CYA, the concentration of HOCl is instead determined by the CYA-like equilibrium that has charged species on both sides of the equation so the ionic strength effect is cancelled out. )

[fcfrey]

So ---- What have we learned??

After nearly two months, 90438 Characters (with spaces), making up 15683 Words, in 45 posts from 12 different contributors including our Administrator and Moderators, we have had a very spirited debate. We went over, under, around and some, directly to the question, which in case we have forgotten, “Is it safe to swim with an elevated chlorine level?”

1. We have explored the politics, the fears, the fear mongers in the “Greenie” gang, and the chemistry behind effective chlorination.

2. We’ve also discussed the way our mainstream media runs off with half of the story and creates the rest itself, true or not, to “sell papers”. Ben has very accurately pointed out the fact that “the fears that people bring to the Pool Forum are not, for the most part, irrational fears. Rather they are a rational response to the persistent and hyped anti-chlorine hysteria shrieked out by modern environmentalists and uncritically parroted by the mass media”. The latter being one of the most profound statements of the entire thread.

3. We have learned that there are many forms of disinfection available for our pools including sunlight, UV, peroxide, bromine etc. etc., but none do the job as effectively as chlorine.

4. We have learned that the real dangers are from the disinfection by products (DBPs) and Tri-Halo-Methanes (THM) particularly in indoor pool environments, but these problems really do not apply to our outdoor residential pools where there is plenty of ventilation. In addition the fear of chlorine being directly absorbed through the skin has been largely debunked, but there is evidence that some halogenated compounds -- that may, or may not be present in pools -- can be so absorbed. We should, however, keep in mind that these compounds are found in pools in many forms including salt and the very liners that keep the water where it belongs (in the pool).

5. We’ve discussed lighting and algae formation in aquariums and the relationships to disinfection and sanitation.

6. We even discussed DDT.

7. We have learned that there are some members of this forum that are overly sensitive to what other members quote and are willing to lash out with concealed retribution, leaving the recipients with their “feel bad” hurt.

8. We have learned that there is a need for compassion for the “unlearned” and those skeptical of the principles and practices taught here.

9. And finally, we have gone --- w-a—y off topic to explore the area under CarlD’s bed

But what about the question-----------------?????

I think it is safe to say, “that all depends”. It depends on who is doing the tests, and are they accurate. It depends on how high your cyanuric acid level is. It depends on the level of your chloramines (combined chlorine). It depends on every other chemical we put into the pool. It depends on the environment in which your pool exists. But it really depends on how comfortable you are with what the administrators, moderators and other contributors on this forum believe.

For me --- nearly two months after posting the question, and reading another 1000 or more posts on a lot of related subjects, I will now swim in my pool whenever it is 10 ppm free chlorine or less. I’m comfortable with that decision, a decision that I probably would not have been able to make without the debate that my question has brought forth.

I’ve added another 656 words to this thread so I need to bring it to a close.

Lastly --- I feel compelled to thank Ben, for providing this forum. Richard, for his detailed chemical explanations and charts. The Moderators who keep things going forward with their great advise. And finally all the newbies, some of whom ask some of the most ridiculous questions (sometimes they make me laugh) which bring out the very best information money could never buy.

Frank