Chlorine Lock ????

[chem geek]

Chem_Geek, Waterbear, Mods, Marie? have you got any other ideas?

Carl,

For some reason, there's been quite a few reports of unusual chlorine demand on multiple forums. Some of them have clearly been ammonia issues and most of them got cleared up with the demand going away once the ammonia and resulting combined chlorine (after adding chlorine) were eliminated. A few have persisted with continued chlorine demand and I, too, am at my wits end to know why.

It does not appear to be nascent algae growth as phosphate levels are nil and the water is clear in these cases (and bucket tests don't show algae blooming). In one case, the chlorine loss is only during the day so appears to be something like bromine, but the loss was quite rapid -- faster than one would expect with bromine and it was verified that there was CYA in the water.

One obvious thing would be to make sure that the skimmer and filter are cleaned out since lots of small organics (such as pollen) would create a high chlorine demand. In theory, one would only see such demand during running of the pump.

I think your recommendation of a concentrated chlorinating liquid effort on a frequent basis is reasonable. I would, however, like to know with some certainty whether the FC loss in this case occurs primarily during the day or if it also occurs overnight. Also, if chlorine gets added and the FC drops very quickly, CC then goes up, and then CC goes down in about an hour or so, then that would likely be oxidation of ammonia (though I don't know why it wouldn't show higher in an ammonia test). Also, it seems like we've only got some pool store numbers for things like CYA -- it would obviously be much better to confirm the water chemistry parameters with a known good test kit such as the Taylor K-2006 or the TF100.

Richard