CYA very high but algae managed, will these numbers cause continuing problems?

[BudPool]

30K Gal (30*20, average depth about 6.5) Plaster
Bleach (now, pucks before)

Taylor 2006 Kit (not 2005)
FC 28
CC Less than 1
PH 7.2
TA 100
CH 325
CYA 150

I was using some test strips before I found the light with this place and a good test kit, and either they were bad, I was colorblind, or something, but about six weeks ago I put in way too much CYA. 10 days ago drained about 40% of this thing and refilled (so CYA had to be above 200 at some point).

After the drain, I shocked it by TFP standards (Chlorine 45) and knocked out the algae.

Don't want to do a big drain again until the next water bill.

Algae is managed right now, pool is open and is in constant direct sunlight.

Is that CYA number going to continue to be an issue? How slowly is it going to decrease due to losing water to evaporation, etc.

Any advice for a pool like this and these numbers outside of pool school would be very appreciated.

 

[JasonLion]

Welcome to TFP!

That depends on knowing what the PH actually is. Essentially none of the common PH tests can measure the PH when the FC is that high. If the PH is indeed 7.2, then you are doing alright. But if you used a standard PH test and it read 7.2 you have a problem, because the PH is not going to be anywhere near what it reads when FC is 28, and thus is presumably dangerously out of range.

CYA does not go down due to evaporation. CYA mostly only goes down due to water replacement. If your filter requires backwashing, or you splash out water, that will lower the CYA level. CYA also goes down very very slowly due to CYA being broken down by chlorine, but that is going to take a year or more to get CYA down to something more manageable.

 

[borjis]

Essentially none of the common PH tests can measure the PH when the FC is that high.

I've read this here before.

At what level of FC is the maximum allowed, to get an accurate ph test result?

the TFP calculator says my pool should have FC of 12-19 ppm

 

[BudPool]

Welcome to TFP!

That depends on knowing what the PH actually is. Essentially none of the common PH tests can measure the PH when the FC is that high. If the PH is indeed 7.2, then you are doing alright. But if you used a standard PH test and it read 7.2 you have a problem, because the PH is not going to be anywhere near what it reads when FC is 28, and thus is presumably dangerously out of range.

CYA does not go down due to evaporation. CYA mostly only goes down due to water replacement. If your filter requires backwashing, or you splash out water, that will lower the CYA level. CYA also goes down very very slowly due to CYA being broken down by chlorine, but that is going to take a year or more to get CYA down to something more manageable.

So keep draining to waste and refilling to lower cya. Cartridge filter.

Um, is there a test to figure my actual PH that I can do? I assume pool store won't have it, right?

Pool right now looks very blue, cloudier than I would like. Also, I'm 150 minutes South of Tampa, so it is hot year round.

 

[JasonLion]

The PH test is considered reliable at FC levels up to 10. At levels up to 15 the results are usable, but tend to be higher than actual by .1 to .3. At levels around 18 to 21 (and higher) the PH results stop having any useful relationship with reality.

Electronic PH meters don't have these problems with the FC level. However, they have challenges of their own. Inexpensive PH meters tend to be useless. Mid-priced meters are alright if you use a multi-point calibration regularly. Some of the more expensive electronic meters are quite good, but the price is considered prohibitive, and again they need regular calibration.