Risk of bleaching liner with SLAM?

[Mike434]

FC 7.2, pH 7.6-7.7, TA 90, CYA 50 (CYA from pool store electronic test)

I have an algae problem and need to SLAM my pool. Based on the chart Chlorine / CYA Chart - Trouble Free Pool and my CYA level (which I find impossible to test myself as I ALWAYS see the little black dot!), I need to bring FC up to 20. The Problem: I have a new vinyl liner that I’m nervous about bleaching at such a high level. Assuming I add liquid chlorine carefully in the deep end of the pool with the filter running, can I be reasonably assured that I won’t damage my liner? Thanks.

 

[JoyfulNoise]

You should confirm the CYA number. If you are "always" seeing the black dot then that means your CYA is lower than 30ppm. Meanwhile, your pool store testing is saying 50ppm. Given that pool stores are notoriously careless with stabilizer measurements, you might want to trust your own testing. If your CYA is truly below 30ppm, then you need to get it up to 30ppm for a SLAM and you can use 12ppm as your shock level. The FC/CYA ratio for shock level is 40%. That is actually quite harmless to vinyl liners. Pool service companies will often come and dump a lot more chlorine into the pool than that when trying to clean up an algae issue.

So, as long as you get your CYA right, SLAM'ing your pool at TFP suggested levels will not harm your new liner.

 

[Divin Dave]

Hi Mike,
there is no risk what so ever to your liner with the FC at slam level.
If there were, half the people here on TFP would have bleached out liners.

 

[Mike434]

Thanks so much! I guess I’ll just keep practicing that CYA test. Back to the sun. Tube at waist height. I’ve read the advice. I just wish there were a titration.

 

[mknauss]

I just wish there were a titration.

Don't we all!

 

[aussieta]

the way i do the test
mix up sample as normal
fill tube to 100
hold tube at waist level back to sun
have a glance, no more than 2 or 3 seconds
if you see black dot, fill to 90 and repeat