Add CYA before starting SLAM?

[MNiels]

After 28 days with no power to the pool pump, we finally have power and a working pump and filter. In spite of brushing daily and maintaining pH and FC, we have an algae load and will be doing our first major SLAM. We're familiar with the process per Pool School but have one question before we start. The CYA is less than 30 and is possibly zero. Should I add CYA to get to 30 ppm before starting the SLAM? Wondering if, without CYA, all the SLAM chlorine will dissipate before it can kill the algae?

 

[Texas Splash]

Should I add CYA to get to 30 ppm before starting the SLAM?

Yes. Without stabilizer the chlorine is exponentially more harsh. Plus, the chlorine needs some protection from the sun. FC will disappear very fast without that protection.

 

[MNiels]

Thanks for quick reply, I'll add CYA now. What's baffling is that we've been able to maintain FC at not less than 6.5 with 0 CC all this time; I didn't expect that during a full algae bloom and falling CYA. Sure hope my CYA testing is accurate (the reagent is in date).

 

[Texas Splash]

Sure hope my CYA testing is accurate (the reagent is in date).

You can always err on the side of caution by adding 20 ppm and re-test in 24 hrs or so.

 

[MNiels]

Thanks, will do. Gotta go find a second sock - my CYA sock only holds enough for 10 ppm

 

[mgtfp]

Did you get a lot of rain during the 28 days without power? And did you let the pump mix the water for a while before testing CYA? Maybe you still had a more rain diluted water layer swimming on top?