End SLAM, Overnight Test and Marble Dusting

Earthman Bob

Bronze Supporter
Mar 25, 2019
88
Long Island
Background: At the beginning of June, I hired a pool company to marble dust our pool. At the time, they said they were three weeks out. So I figured I would leave the pool closed until they did the work. I was busy and figured (apparently incorrectly) that they would be blasting the surface anyway. I then spoke to them late June and they said we were scheduled for just after July 4th. That didn't happen so last week I spoke to them and they said the end of this week or next week. This time I think their estimate is accurate.

When I spoke to them last week, they informed me that the pool surface needed to be algae free before they started their work. So I had the choice of either SLAMMING it or emptying and power washing the whole thing. I chose to SLAM, thinking we'd maybe get a week of pool use in. Started on Friday evening. 4-1/2 days later, SLAM went great. Pool water is clear as of yesterday. CC is zero.

Question: I was not able to do the overnight test last night the right way, due to my work schedule. I tested it at 4AM and then again at noon today. The FC had dropped by 2. It was sunny this morning. If I wasn't trying to shave a day off the process, I'd continue the SLAM today and do a good test overnight. Given the circumstances, do you think it's safe to let the FC drop now so we can start using it, or should I continue SLAM one more day? If I was able to get a good overnight reading, I wouldn't be asking.

Thanks for your help in advance!
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
20,477
Northern NJ
You don't say what your CYA for SLAM FC level is.

The pool is safe to swim when the FC level is below SLAM FC level. So let the FC level drift down 2-3ppm below SLAM FC level, go swimming, then raise it back up to the SLAM FC level after swim time is over. Repeat as necessary.
 

Earthman Bob

Bronze Supporter
Mar 25, 2019
88
Long Island
You don't say what your CYA for SLAM FC level is.

The pool is safe to swim when the FC level is below SLAM FC level. So let the FC level drift down 2-3ppm below SLAM FC level, go swimming, then raise it back up to the SLAM FC level after swim time is over. Repeat as necessary.
Thanks for the response. I tested it again the night after I wrote this, and the drop was good. So I ended the SLAM, adjusted other levels, and am now officially starting part 1 of the season, just in time for a very hot weekend!