First time SLAM. Few questions.

[Jlsergent]

My pool is 16,000 gallons and looks great. Crystal clear. CYA is a little high. According to the TF 1000 it looks to be 70 if I can trust my eyes on that test! I've practiced a few times. Pool isn't holding chlorine. Adding 3 gallons a day. Is that normal?
I read some others suggested to SLAM the pool and i understand I'll need to get it to shock value at 28 ppm or so. Adding liquid bleach. What I don't understand is what do I do after I add all those 7+ gallons. I'm testing it for what? Am I trying to keep it at 28 ppm? For how long? Directions for SLAM says to test at least twice a day but I don't know what I'm looking for it to do.
Thanks!

 

[YippeeSkippy]

What happens when you add all that bleach (check your numbers using poolmath first!) is any algae in the water will immediately start chewing up thru that bleach and lower your FC level over time. Like, an hour?? So we tell folks to re-test and re-dose as often as possible (especially at first when the algae killing is going faster) as the more time spent at SLAM level, the faster the entire process of killing all the spores will go.

When the pool is then crystal clear and no sign of algae, do you perform an OCLT to determine if your SLAM is over. Overnight Chlorine Loss Test

Maddie

- - - Updated - - -

Brush brush brush also! That disrupts any algae spores hidden under biofilm attached to walls and lights, etc.

 

[Jlsergent]

So how long do I keep adding bleach to keep it at the shock level? Let's say I get it up to 28 ppm (shock level based on my cya) and then 2 hours later it is down to 24 ppm. do I add more to get it back to 28 ppm? How long do I do this? Is the point of the whole thing to get it to shock level and keep it there a certain amount of time? I'm still very confused on what my goal is.
I checked the pool calculator to see how much to add to get it to 28 ppm.

- - - Updated - - -

By the way my pool already is crystal clear and has no signs of algae.

- - - Updated - - -

By the way my pool already is crystal clear and has no signs of algae.

 

[JV63]

Yes, you would raise it back up to 28.

With a CYA of 70, I don't think you should be having to add 3 gallons of bleach each day, which would point to there being algae somewhere in your system eating your chlorine. It could be behind a light, on steps, around skimmer any lower flow nook or cranny is suspect.

You are finished when the water is clear, cc is .5 or lower, and you can pass the overnight chlorine loss test.

 

[YippeeSkippy]

JV63 is Right! Something in there is chewing up all your FC. It just hasn't shown you its hiding place yet.

Maddie

 

[Jlsergent]

Thank you! I will start the SLAM soon. Water is already clear so I will just keep it up to shock level until I pass the overnight test.
I did test the CYA today and it is considerably lower than the last time I checked. It may be me learning to read that test. But I swear I did it the same way last time. And I was careful. Two weeks ago it was in 70 range and today I read it at 50. We have had a LOT of rain. Could it really drop that much?

 

[Razorhog]

Thank you! I will start the SLAM soon. Water is already clear so I will just keep it up to shock level until I pass the overnight test.
I did test the CYA today and it is considerably lower than the last time I checked. It may be me learning to read that test. But I swear I did it the same way last time. And I was careful. Two weeks ago it was in 70 range and today I read it at 50. We have had a LOT of rain. Could it really drop that much?

With a lot of rain it could drop that much - take into consideration also that the CYA test has a considerable margin of error.