Given the care routine you described, last year, you were very lucky. This year, not so much.
You're going to have to do it right . . . or get very, very lucky.
1. Go get a cheap OTO / phenol red test kit (yellow / red drops) Teststrips are not dependably accurate for the most part. Old test strips are dependably inaccurate. All test strips are virtually useless at measuring stabilizer, which is critical.
2. 16' x 4' pool => ~4,800 gallons or PF of 25. So, 1 gallon of 8.25% bleach (~0.7 lbs chlorine gas), will add 25 x 0.7 ppm or 17 ppm of chlorine to your pool.
3. When you get the kit, buy 5 gallons of PLAIN 8.25 household bleach. Add 1/2 gallon of bleach in the EVENING, this evening if possible.
4. Test your chlorine in the AM. If you do not get a DARK yellow OTO result, add another 1/2 gallon.
5. Test your chlorine in the PM. Dose as above (1/2 gallon, unless you have a DARK yellow OTO result).
6. Continue this until your AM result is very DARK yellow.
7. Meanwhile, test your pH before you add your first dose of bleach. (High chlorine messes up the pH test). If the pH is between 7 and 8, you're fine. Otherwise, that will need to be adjusted to.
8. If you aren't already, run your pump 24/7.
9. List all the chemicals you've used in the last 2 weeks, and post them here, along with your test results.
10. High alkalinity does not affect chlorine level. It can lead to cloudiness, if you ALSO have high calcium. (Have you been using calcium hypochlorite shock? See #9 above)
11. What sort of filter do you have?
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