unable to maintain chlorine levels

[PoolDoc]

Thanks for the page numbers -- I've printed that out, and will look at them.

. . . Now. Ignore all that stuff that I asked about; those are useless metrics.

I’m still experiencing small algae recurrences.

Questions, if I may:

1. Which recommended guidelines is best to use, APSP or NSP, for my situation?

Neither. Both include unnecessary calcium recommendations, and do not adjust chlorine levels for CYA level. (Do you mean NSPF?)

2. Which guideline should be use for total alkalinity, given a salt system… 80 to 100 or 100-120 ppm?

Lower levels are less likely to scale.

3. Please explain PHMB (listed on the guidelines) versus pH? The kit doesn’t test for PHMB. Should I bother with it?

It's Baquacil. Ignore it. Had nothing to do with you.

4. How do I use the CYA Stabilization number? What is the min, ideal, max scale.

Ignore it. Read the Best Guess page, linked in my signature.

5. Ditto the Saturation Index?

Ignore it.

6. My 80° water temp is unusually low now due to record low temps and rain this summer. Usually struggle to keep it below 90°. What is most important criteria to watch for when water temp is that high?

Maintaining appropriate (Best Guess) chlorine levels.

7. I’ve always been told Calcium should be zero or as low as possible in vinyl lined pools. True or not?

Not true. On a vinyl pool you don't need to ADD calcium but you don't automatically have to lower it, either.

[Coman]

Whew. Trying to wrap my head around a different chart.

So, if i read your chart correctly, for FC=3.0 and CYA=45, i should be OK. Right? Or, should i raise chlorine closer to 6 to suppress the algae growth?

How should I use your chart in conjunction with pH and TA measurements. if I understand you, those are the only 3 I need bother with. Correct?

BTW, thank you for taking the time to explain the long versions. I'm sure you've done it over and over. But it is very helpful. we budding backyard chemists appreciate it.

[PoolDoc]

EDITED:

If you have algae, you should raise the chlorine levels to the algae level. Otherwise, it's not needed.

HOWEVER, losing chlorine suddenly tends to indicate beginning algae. I'd recommend going ABOVE the algae level for chlorine, then brushing the pool completely, and then holding at the algae level, until overnight chlorine loss is minimal.

With no stabilizer, pH levels have a big effect on the 'activity' of the chlorine present. After stabilizer, not so much. Alkalinity doesn't directly affect chlorine.

Regarding repetition: it takes a surprising number of repeated explanations to begin to optimize that explanation so that it usually communicates the key information effectively. But, this winter I am hoping to be able to 'migrate' a number of the oft-repeated (and now 'mature') explanations to static PoolSolutions pages, and just link them, from here.