Holy Chlorine, Batman!!

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Originally Posted by PoolDoc

The Taylor reagents are stabilized against chlorine, but not to 44 ppm. As far as I know, the only reliable method of testing pH, when the chlorine is that high, is a RECENTLY CALIBRATED pH meter.

Ben
"PoolDoc"

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DITTO THAT, Ben! At that high a chlorine level just about all the phenol red would probably have converted to chlorphenol red which is yellow at a pH of about 5.0 and turns purple at a pH of about 6.6 with shades of orange, red and red-purple in between, similar to phenol red from ph 6.8-8.2. So, if the pH appeared to be about 6.8 (yellow orange with phenol red test block) it was probably MUCH closer to about 5.2!!!!!!!!!!!!!!!!!!!!!!!!!!!) Trichlor is VERY effective at lowering pH, as we all know too well ;)
Once the chlorine level started to drop to 22 ppm then the sodium thiosulfate in the pH indicator might actually have had a chance to kill some of the chlorine and less of the phenol red would convert. Hence the apparent jump in pH. I would have to guess the pH was STILL probably at or below 6.0 however. The indicator color would be a mixture of both the phenol red and the chlorphenol red in some unknown proportion at this point so the pH reading is still probably bogus.

This may be worth nothing also, but what this gent experienced does not surprise me....


If one relies soley upon what pool stores are telling clients, and if one does not know first hand the basic chemistry involved (thank goodness I found this site and forum!), one could easily end up in this siuation not knowing what the problem is.

I recently went to a 'pool school' sponsored by a reputable pool compnany here in town. The seminar was given by a salesman for one of the leading pool chemical companies.

I was astonished at what the guy was telling the group as 'facts'. He was advocating the sole use of their sanitizer sticks to maintain chlorine levels in the pool. I asked what would happen to stabilizer levels if one followed that practice. I was told outright that 'scientific tests performed by their company have confirmed that stabilizer levels have no effect on the ability of chlorine to sanitize, and that the levels can increase to very high levels (several hundred ppm) with no consequence on the efficiency of chlorine". He reassured the group that one could use their sticks for many years before pool water would have to be replaced to reduce stabilizer. Top that with the fact that he never warned about having to increase chlorine levels to 'achieve' efficiency as stiabilizer builds up, and that the usual test strips and kits can give false readings of chlorine at levels above 10-15 ppm due to bleaching.......Im sure a large number of those naive pool owners are going to exericene this same problem...