Owing my mistakes with CYA & SLAM, have questions

TBalcom

Active member
Aug 15, 2016
32
Tacoma, WA
In my excitement to get the pool opened and get the SLAM started (last week) so my kids could swim with friends at the end of this week (the water was nearly clear, I deep cleaned the sand filter, and there was very little debris) I jumped the gun on the CYA and added it BEFORE finishing the SLAM process, bringing my CYA up to 80. I read the instructions wrong and I totally own it. Because of that mistake I've had to use almost 5x the bleach to keep FC @ 31. Yesterday I added the recommended amount of bleach (test read 27 and Pool Math app said I only needed a quart + 1 cup of bleach to bring it back to 31 even though it keeps telling me it is out of the suggested range - is that because the CYA is too high for a SLAM?) and when I checked it before I went to bed the FC was at 40!!! This morning it was 36 and this afternoon it's still at 36. The water is still crystal clear and I will do another OCLT tonight.
My questions are:
Can I SLAM with such a high CYA? Or do I have to drain some of the water? (we had a pump leak the first week and lost almost 6" of water so I've already had to refill some)
Should I be running the SWG during the SLAM? Or just rely on the liquid bleach?
I've read a number of people asking "when can we swim after a SLAM?" and the answer is when it's within the SLAM range for my CYA - but Pool Math App is telling me the target is out of range. I know that 36 is higher than the recommended 31, so I'm assuming no swimming until I can get FC down. I took off the cover today to allow the sun to "eat" some of the chlorine.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
29,261
Laughlin, NV
Poolmath is saying the FC you are targeting is 'out of range' because you are not in the target range. When you SLAM, it will always say that. Ignore it.

You can SLAM with high CYA, just takes a lot more bleach to start and alot of reagents to test.

We recommend you NOT run the SWCG during the SLAM. It definitely needs to be off for the OCLT.
An OCLT at very elevated FC levels can be problematic. Testing error is significant at those levels. That is what you found when you tested the 40 ppm.

They can swim up to the 31 ppm FC. But you might be better off having it a bit below that as there is error in your CYA and FC test. Or just be sure they wear old swim clothes. They might fade a bit.
 

TBalcom

Active member
Aug 15, 2016
32
Tacoma, WA
Thank you @mknauss . I just retested everything because I don't trust the numbers as they've been very unpredictable. and as I suspected, they changed again!
  • FC: back up at 40.5 (good thing I bought a huge container of reagent last year!! 80 drops per test is ridiculous!)) The tester tipped over as I was going to do CC but in the last 5 or so tests it's been 0 or barely 0.5.
  • My pH was 7.6 which seemed odd, but I do remember reading that pH levels are not reliable during SLAM. And this is one test I hate because it requires ME to tell the difference between minute differences of orange and pink! Can't someone come up with a drops test that will change between two dramatically different colors like the salt one does!? ;)
  • TA has been consistently 70 but today I couldn't get it to turn red AT ALL! It went from green, to a light blue, to yellow, never red. Not even pink. I tried twice, once doing the 25ml test and again with the 10ml test. Nothin'.
  • Calcium (for what it's worth, although I have a vinyl pool) is approx. 50 (4 drops = purple, 6 drops = true blue)
  • CYA - which has been reading 80 all week now looks more like 65 or 70. I did this one a few times to double check but I used the same mixture, does that matter?
  • Salt - 3200 - I'm going to wait to add any more until the SLAM is done.
 
Last edited:

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
29,261
Laughlin, NV
TA test is messed up with the high FC. From Pool School: Continue adding drops until the color changes to something more or less red, pink, yellow, or clear. The sample may switch between green, blue, and gray while you are adding drops. That is not the color change you are waiting for.