RASSRQ

[RASSRQ]

I have just done an iron-stain removal with ascorbic acid, which meant that Cl had been at 0 for a while, and the water had become somewhat milky cloudy, but not terrible.

I started shocking noon the day before yesterday, bringing FC to 24 and maintaining it there through yesterday. So, this morning, which is after the 2nd night, last night showed zero FC loss (FAS-DPD test) and CC is no more than 0.5.

The milky cloudiness increased drastically as soon as all the chlorine was first added. The cloudiness is improving, but not yet clear. But the SLAM description in Pool School says that cloudiness may take a week to clear, and I have a paper cartridge filter so I do expect that to be somewhat slow.

Since chlorine isn't being lost on the overnight test, indicating there's nothing it needs to attack, and CC meets the goal, is it really necessary to top off chlorine (which will be lost to sunlight) to shock level until the water is completely clear, or can I start letting Cl come down while the cartridge filter slowly clears the water?

Thanks in advance ... Bob

 

[chem geek]

If the cloudiness is algae growth that hasn't clumped enough to look green, then you need the chlorine level to be well above normal levels in order to get ahead of that growth. The reason is that significant algae consumes chlorine locally so algae inside any clumps doesn't get exposed to chlorine and can grow. So you need a higher level so that it doesn't run out and so that it can kill algae faster. Otherwise, the pool could take a very long time to clear.

On the other hand, if the cloudiness is due to something other than algae, then 24/7 filtration is more important than the chlorine level. The overnight chlorine loss test is not definitive in distinguishing algae from something else, but it does sound like if there is algae, it's not consuming much chlorine, so perhaps you are safe in letting it drop somewhat. You can certainly watch it and if it looks like it's blooming again or not clearing then it might be growing again. I wouldn't go down all the way to normal levels, however -- try keeping it still elevated even if not at shock level. This would not be the SLAM process, however, and I would not recommend it -- I'm just answering your question as to the risks of the alternative you propose.