Quote Originally Posted by Indywar View Post
But anyways, the sodium chloride (salt) is measured by a dipstick and/or a conductivity meter, not by any chemical means. The pH probes is indeed calibrated with Fisher scientific pH 4 and pH 7 standards (I am a chemist and microbiologist during the day, and easily have access to the expensive pH meters to have an orthogonal technique to compare my pH probe to. In addition, I have used the phenol red (significantly less sensitive than our pH meters), yet another orthogonal technique, to confirm the pH probe readings).
Not the response we usually encounter! But, you did lead me astray with this:
I measure the chloride using the drops (HTH 3 way kit)
(Shame on you!)

Shocking is not the hazard it's made out to be. People are very chlorine resistant -- though swimwear is not!

Anyhow, we'd gradually been moving toward a full blown rejection of all the NSPI / APSP / CDC / EPA "Keep people out of the pool till the FC is less than 3 / 5 / 10 ppm", though we hadn't quite gotten there. Now, we have.

I've known for some time that those regulatory limits were pulled out of the air. But until recently we didn't have positive confirmation of the safety of high levels of FC exposure. But, we had the issue raised this spring, and in the investigation that followed, I found that an old dermatological treatment, a "bleach bath" (> 50 ppm FC), is STILL actively and regularly prescribed for a variety of skin problems. Here's the link to a Google search on the topic.

So, when you shock, let it circulate long enough so their suit (or eyes) won't hit a hot spot . . . and you're fine!