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[LNRanch]

Every year it seems...I'm in Southwest Tx. May had 15+ triple digit days then a heavy rain. When that rain came my pool went to Crud. The CYA read high (although no empty/refill has ever fixed our "high" cya readings). So I drained the pool, refilled. Balanced the water. I've only used bleach. Pucks are in the inline chlorinator but I use only a few (5 every 3 weeks or so). My FC is 15.5 , pH 7.2, alk 60 (I added muratic acid to get pH down), cya still reads at 90 even after 2/3 drain but even at 90 a FC of 15 is far higher than needed (and FC it's coming down...I slammed 2 d ago to get it to 20). This whole scenario occured last year as well after a huge rain and I drained my pool 3x. It NEVER lowers the cya reading. I'm using the TF 100 kit. Anytime I need increased CL I use bleach...not pucks or shocks that increase cya. It's in full sun, I do everything in the eve as the sun goes down....my filter runs 24hrs a day (glass medium filter) and my dolphin nautilus cleans all day. I'm ready to fill this thing in grrrr

 

[Texas Splash]

Did someone say HOT! It is. To be sure we all understand, the rains won't do anything to lower CYA unless you lower the water level in advance of a heavy storm. CYA doesn't dilute, although a small of CYA (about 3-5 ppm) may degrade and go away each month. But above you mentioned using liquid and tabs - 5ea every 3 weeks or so. If one puck adds about 6-9 ppm of CYA, then each month you're adding anywhere from 30 - 45 ppm of CYA. You can confirm this by using our PoolMath APP's "Effects of Adding". You have to cut the cord completely from tabs - for now.

For algae, you must perform the SLAM Process until you pass all 3 SLAM criteria. Hope that helps.

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[LNRanch]

I have zero issues all year. This happens only in beginning of summer after a big rain. I use bleach because to keep my chlorine levels where I need them in this sun, my cya would be 1000. My cya always reads 80/90 even after I drain and refill my pool. I'm unsure why. Even after I fix this issue each year, that reading never changes. However, I've done the Slamm process 2x now, nothing is changing. The water is green. No algae is growing on walls etc but I cannot get the water back to normal. A FC of 20 is double the FC needed in a cya of 80/90. I've hit it twice with the pH and all balanced according to my testing kit.

 

[Texas Splash]

So let's recap a few points of interest:
- New/fresh water has no stabilizer (CYA) in it. If you were to do a 100% drain, your new CYA would read as zero.
- Liquid chlorine/regular bleach has no stabilizer in it.
- Any CYA in the water right now means pucks/tabs were recently (or still being) used or means a previous partial water exchange still had residual CYA in it.
- Pool owners who used tabs or powdered shock products in the past may have had a CYA so high that even an 80-90% water exchange still resulted in a high CYA level.
- Rain has vey little to do with getting algae.
- When the proper FC-to-CYA ratio (7.5%) is consistently maintained as noted on the FC/CYA Levels, it is very difficult for algae to grow.
- Even when the water is clear, algae can be growing in places not inspected such as in ladders, under hollow stairs/steps, behind a light in the niche, etc.
- For those who had algae in the past, if they didn't perform a SLAM Process thoroughly and until completion of all 3 criteria, odds are the algae was never completely removed.
- If ever in doubt about algae or excessive FC consumption, the first step should always be to do an Overnight Chlorine Loss Test.

 

[PaigeMark]

I have zero issues all year. This happens only in beginning of summer after a big rain. I use bleach because to keep my chlorine levels where I need them in this sun, my cya would be 1000. My cya always reads 80/90 even after I drain and refill my pool. I'm unsure why. Even after I fix this issue each year, that reading never changes. However, I've done the Slamm process 2x now, nothing is changing. The water is green. No algae is growing on walls etc but I cannot get the water back to normal. A FC of 20 is double the FC needed in a cya of 80/90. I've hit it twice with the pH and all balanced according to my testing kit.

I’m new to all of this and still figuring out CYA issues. Have you tested for CYA of your fill water?


Edited: Didn’t realize that fresh water has no CYA.

 

[MITBeta]

I slammed 2 d ago to get it to 20).

That's not SLAMing. That's shocking. For a CYA of 90, your SLAM target is 36ppm FC. Keeping tabs in the chlorinator isn't helping, either.

 

[Deb04]

Don't use any more tabs. That's only going to continue to raise your CYA.