SLAM...Am I doing this right?

[labelle]

I'm doing a SLAM on my pool and yesterday I added bleach to get it to shock level. After an hour, it was maintaining shock level so I tested again two hours later and it was still maintaining shock level. That was my last reading before bed.

When I tested FC today (not until the afternoon), it had dropped from yesterday's shock level but not as much as I would have expected given how green the water was yesterday and that there is still visible algae....and it was sunny today. I would have expected the FC to drop a lot more, however, it went from about 28 to 22.5. One variable is that yesterday my CYA level was a bit high. Before shocking, I lowered the water level a few inches and then put the hose in the pool for about two or three hours. The hose was in the pool while I was adding bleach, however, by the time I last tested late in the evening, I had taken the hose out.

Today's reading of CYA is about 45 which means that target shock level is now 16 if I'm understanding this correctly. Since FC was already at 22.5, did I need to add more bleach?

Also I thought I read somewhere that CC can get very high when FC is at shock level. Is that true? I got a reading last night that was so high I was ready to look for zombies in the pool.

 

[Divin Dave]

Hi labelle,
adding bleach to get to SLAM level is the right thing to do, obvoiusly.
With your CYA of 45, you SLAM FC is actually 18. (SLAM level FC is 40% of cya...so 45*.4= 18)

you did add to much bleach bringing up the FC to 28, but its ok. Dont worry about it. You dont need to add any more until you reach 18.
the M in SLAM means MAINTAIN. So, in order to MAINTAIN slam FC of 18, you really need to add a couple more ppms of Chlorine so it will have some head room to go down some as it kills algae.

If your pool is green, you expect to have lot of CC.

You probably remember reading that with FC above 10, that pH will read a false positive high (not the cc's) SO, no need to test pH when slamming as it will be a false test.

hope this helps