Where did my CYA go?

[jimsky]

Took off the cover today. Green but could see the bottom in the shallow end. Got the filter up and running and started to hammer the pool with bleach. Brushed the whole pool. Turned the Stenner on too and let it run...so I'm getting chlorine into the pool. I didn't need to add any water to the pool at all. I do a water test:

Ph: 7.4
Alk: 60
FC: 30
CC: 3.5
CYA: less than 30

Last year opening you guys helped me see the light. I stopped using bagged shock and pucks and used bleach exclusively. With water exchange I got my CYA down to 45 and with the Stenner maintaining the pool last year was a breeze with no algae the whole season. I knew with removing water for the fall closing and rain/snow refill during the winter the CYA would go down some more, but I can't read anything, tried 3 times. The CYA tube is full to the top and the black dot is sharp and clear.

So I guess I'm going to have to add CYA. I left my puck chlorinator in the system when I added the Stenner. I got a bucket of pucks and a large bucket of shock as shown in attached photo. I know the pucks have CYA, not sure about the shock. Is using one or both of these a viable method of raising the CYA level while I'm slamming the pool?

I just check the FC and it dropped down to 8, I need put more chlorine in the pool but the question is bleach, pucks or shock.

 

[Richard320]

The shock is 73% Cal-hypo. It has no CYA. It will raise CH, which you didn't list Low CH won't bother your vinyl pool, but high CH can still cause scale in it, so be careful.

The pucks will add CYA. They will also affect pH and lower TA some.

Effects of Adding Chemicals down at the bottom of poolmath will tell how much each affects things. While you're using poolmath, set up your chlorine source to trichlor if you do use the pucks, because you'll need to pay attention to TA. I see baking soda in your future.

 

[jimsky]

Well the green pool I had yesterday is now blue today. Vacuumed and chucked in the robot. I've got the chlorinator filled with pucks running at maximum. Latest water results:

FC: 9
CC: 0.5
PH: 7.0
TA:50
CH: 90
CYA: less than 30

 

[Richard320]

If your CH is really only 90, you can use quite a bit of that Calhypo shock before CH becomes a problem. Like, all 50 lbs of it. Target 12 FC and let poolmath calculate how much of the Cal-hypo 73% you need to get to shock level. When the bucket is gone, whether or not you're done with the SLAM, switch to bleach.