Newbie with Algae, SLAM, and chemical questions

[JeffRH]

First time posting here. I have been testing my own water for years but only recently obtained a FAS-DPD test. I have typically been using Leslie's shock and floater tablets. Learning more from this site with a plan to switch to liquid chlorine. Also just subscribed to the Pool Math app.

Currently my pool is clean and clear. But in the last 4 to 6 weeks, especially since I turned the solar heater back on, I have been having some intermittent green algae form on the walls that face NW and don’t get as much sunlight. Have also found it on the bottom of my pool sweep and my weir gate tile leading to the skimmer basket (since removed). A brush and a shock treatment with Leslie’s Power Powder Plus 73 typically gets rid of it but I feel like I am always riding the hairy edge and probably not getting rid of it entirely.

I have a Taylor K-2005 kit and a separate K-1515 FAS-DPD test. Attaching screen shot of test results from last night. I checked chlorine levels early this morning at sunrise and there was no drop overnight but pH increased slightly from 7.6 to 7.7.

Here’s my questions:

1. Does my situation require a SLAM? Or am I better off sticking with what I have been doing for now?
2. When the time comes, what is a SLAM level? The FC/CYA tool says my SLAM level is 24. Does that mean I need to raise free Chlorine to 24 ppm?
3. The app and website base everything on liquid chlorine, which I don’t currently have (but can easily get). I do have 16 lbs of Leslie’s Power Powder Plus 73 and would prefer to use this up before switching to liquid chlorine. Is there a way to calculate the equivalent amount of Power Powder Plus that could have the same effect as liquid chlorine?

Thanks in advance for your input!

 

[mknauss]

You need to follow the SLAM Process. Read the article.
Your CH (calcium) is high so you should not be using Cal Hypo (the Leslies stuff). Use liquid chlorine.
Your CYA is 70. Round up.
Your SLAM FC is 28 ppm. You raise the FC to that level and Maintain it until you pass the three criteria described in the article.

Lower your pH to 7.2 before starting.

 

[JeffRH]

Thanks @mknauss. I have read the article twice before posting. My need for clarification came from (1) I don't meet the 3 criteria at the moment (visible algae, CC level above .5, or loss of 1.0 FC overnight and (2) the article does not specifically define SLAM level = Free Chlorine level. This second point probably seems obvious to writer and others that have been here a while but for newer folks I wasn't sure if this was some convoluted addition of separate measurements. But now I understand so thanks for the clarification.

 

[mknauss]

(2) the article does not specifically define SLAM level = Free Chlorine level.

From the article.
"If your CYA is between 30-70 ppm, then look up the corresponding SLAM FC level using our FC/CYA tool and proceed."

So you go to the chart that is linked, and that gives you the SLAM FC level based on your CYA level.

 

[JeffRH]

Started my slam at 7:45 pm on Friday 6/7 with initial dose of 4 gallons of liquid chlorine. I then added an additional 6 gallons of liquid chlorine on 6/8 and 6/9 with FC ranging between 20.5 and 29.5 depending upon when measured. CC has been 0.5 at most. Total of 10 gallons of liquid chlorine have been added at this point.

Unfortunately I ran out of the R-0871 FAS-DPD Titrating Reagent this morning 6/10 when I went to check the overnight levels. My replacement order won't be here until later this afternoon (this time I ordered 2 oz instead of 0.75 oz). By then the sunlight will have already impacted my levels. Hopefully I won't have to dump in too much LC to get back to SLAM levels.

Good news is that there has been no visible algae and CC as never been above 0.5.