Newbie Shock/CYA Advice

[austxsun]

Newbie here! I just took over chem service from a weekly guy (bought the house/pool a few months back).

In short, I'm trying to shock but the CYA is staying low & I don't have any separate stabilizer at the moment.

More detail: I don't think I'd been adding enough chlorine, so had mild algae growth recently. My CC was at 1 yesterday so I decided to shock. I lowered the PH to 7.3 this morning in preparation. I have 6 jugs of 8.25% ready. My CYA was <30ppm (which is weird because it was a little high just a few weeks back, 70, when we had someone taking care of it for us...but it's been raining a lot since so I assume the 12 in of evacuated water during the time lowered it?). I know it's a no-no per most of TFP advice but I had a box of AquaChem ShockPlus packets from the previous owner & I hate to waste so decided to use it since it said PH neutral & we actually needed CYA. Packets say 1 per 6k gallons so I added 2 & 1/2 jug of bleach (not too far off what PoolMath recommended to get FC to 12). Measured 2 hours later & have FC up to 6 but the CYA is still less than 30. These packets could be pretty old for all I know... does CYA break down over time/exposure? Does it take longer to 'show up' in tests (i.e. should I wait another couple hours & test again), etc.? Any reason I shouldn't add another packet or two to get it up to the desired CYA & corresponding shock FC (12-16 probably)? I also have pucks but assumed the CYA release would take too long on that front.

Thanks in advance!

 

[triptyx]

How are you testing CYA? 12" of rain isn't enough to do a 60-70% water exchange, which is what it would take to lower CYA that much.

I'd stop everything (other than daily chlorination) and figure out what your CYA really is before adding anything with stabilizer in it to the pool.

 

[austxsun]

I perform as listed in the TF100 test kit (7ml of pool water, 7ml of _, shake for 30 secs, pour over black dot until it disappears). My only guess is I messed up my first reading somehow (don't think I've changed anything though...); maybe 70 was lower? Every time I've measured in the last 2 days, I still see the dot at 30. It has gotten better over the day today; latest reading was more cloudy at 30 than it was previously.

I added another jug of bleach & have it up to FC12. Fingers crossed the over night test is good.

 

[Texas Splash]

One thing for sure, the last couple days have been brutal with heat, and it's not letting-up anytime soon. So you definitely want a CYA of at least 30 "if" you have to SLAM. If you see ANY cloudiness or algae like before, you probably will need to SLAM. You can perform an overnight (OCLT) test to confirm. If you have to SLAM, just stick to the SLAM page and you'll be fine. If you pass the OCLT and see no growth or cloudiness, then crank that CYA up quickly with granular stabilizer. While there are times you can get-by with a pool store product once or twice, this is one time you can't afford to wait. The TFP max CYA is 50, but many of us in hotter regions go even higher for our non-SWG pool if the pool gets full sun all day long. My CYA runs 60-70 in the summer.

To increase CYA via granular stabilizer, place the required amount as calculated by the Poolmath calculator into a white sock and place in the poolside skimmer basket. For those concerned about suction flow to the pump, suspending the sock near a return jet or from a floating device will also suffice. Best never to allow undissolved granules to rest directly against the pool surface. Squeeze the sock periodically to help it dissipate. Once dissolved, consider your CYA adjusted to that programmed (target) level. CYA test readings should show a rise in 24-48 hours, however some pools may experience a longer delay to fully register. Best to confirm final CYA in about 5-7 days before adding any more stabilizer/conditioner.

But before you increase CYA over 30, make absolutely sure you are algae-free. Good luck and let us know if you have anymore questions.

 

[austxsun]

Thanks so much for the info! That 24-48 hr delay in CYA readings is exactly what I was initially worried about but didn't see anything about it in the SLAM sections. It's up to 45 right now so hopefully it doesn't climb too much further

 

[Isaac-1]

Good luck on things, and just for the record we don't have anything against using dichlor, just that you have to account for all of its actions (pH, FC, and CYA), it is a tool to be used when appropriate, we just don't suggest it for people just starting off as it is easier to track and balance a single variable rather than 3 at once.