Green pool with clogged sand filter after 2 weeks out of town

[SunnyOptimism]

You need an accurate CYA measurement in order to know where you are at so you can target your FC properly. Please do a dilution test - mix 1 part pool water with 1 part bottled or distilled water and then redo your CYA test as normal. Take the results of that test and multiply by 2 to get a correct CYA value.

[jtran69]

5:30pm, FC=15, pH=7.5. I added 1 gallon of bleach.
I have about 10 ml of R0013 left for one cya mea and will take it when FC is back to 25.

[SunnyOptimism]

You can get 2oz refills and even huge 16oz bottles on Amazon. I have a 2oz bottle that I'm about 1/3rd the way through (16oz is kind of crazy big for a residential pool user).

Good luck and I'll keep an eye out for your CYA result. My fear is that your CYA is crazy high and 25ppm FC may not be adequate for a shock level. Also, when your pool is clear, knowing that CYA exactly will help you target a proper FC keep the algae at bay. If it's really high, your pool may warrant some water draining to help get your CYA down...not fun to dump water but the alternative for an over-stabilized pool is to run at a higher FC level which means more bleach and more frequent bleach additions which can be costly too in the long run.

First things first, get the pool sparkly again, then worry about stabilizer....

[jtran69]

I've done a vac earlier and the water is looking really good now. My kids kept asking if the water is ready yet since its has been 90+ over the last 2 days.

[FormerBromineUser]

Geez! High of 45 today here. Brrr! Let the kids swim! FC of 25 won't hurt them, just have them wear regular old swimsuits. Sorry, didn't realize you were keeping them out of the pool. As long as you have good levels of sanitizer and the water is clear enough to see, swim! As far as I know, algae in a clear, sanitized pool never hurt anybody. Take a dunk for me, sitting here in sweats, sweatshirt, fleece jacket ... and I'm INDOORS!!!

[FormerBromineUser]

I should also add that your pH is now okay to swim in. Your less than 7 pH was not.

[CarlD]

Getting cooler fast here now that it is October...

[Watermom]

but the alternative for an over-stabilized pool is to run at a higher FC level which means more bleach and more frequent bleach additions which can be costly too in the long run.

Actually, pools with a higher CYA usually can get by with less frequent dosing with bleach. Some people deliberately keep their CYA on the high side for this very reason.

[SunnyOptimism]

Actually, pools with a higher CYA usually can get by with less frequent dosing with bleach. Some people deliberately keep their CYA on the high side for this very reason.

Thanks, @Watermon.

I think it all depends on what is viewed as "high" and what set point you use for FC/CYA ratio. I try to follow the 7-11 formula for FC -> min FC level is 7% of CYA with daily target FC level of 11% of CYA.

Once you get much above 100ppm CYA, the 7-11 rule becomes much harder to maintain as my understanding is FC loss rate is not constant but proportional to FC concentration. So, at a higher FC level, you tend to lose FC at a faster rate than at a lower level. That was my point about more frequent additions.

Also, shocking your pool starts to become impractical at CYA levels above 150ppm as the amount of FC needed is quite high. I wouldn't go so far as to say you'll damage anything, but it will be a significant amount of chlorine to add and maintain. At some point, you reach a breakpoint where the cost of all the bleach you'd have to add (and time spent trying to maintain it and measure it) is probably as costly as just dumping half the water and starting with a lower overall CYA.

I'm not arguing against your point as I maintained my pool for quite sometime with my CYA at 90-100ppm, but I have the luxury of an SWCG and don't have to do any jug dumping.

[FormerBromineUser]

Jtran: What's happening?

Rest: Ben, Richard, Lisa?