Near passing OCLT then huge drop


Jun 14, 2021
Little Rock, AR
Hello again,

This last weekend I changed the sand in my filter, retightened all the connections, and drained and replaced more than half the water (removing algae and higher copper levels from previous system).
I tested the water Saturday afternoon and continued with SLAM.
FC 8
CC .5
PH 7.2
Bromine 10
Calcium 50
TA 30

added 2lbs of CYA
1:30pm FC 8, add 1 gallon and 1 qt
7:45pm FC 10, add 1 gallon
10:30pm FC 14

7:30am FC 13
1:30pm FC 7.5 CC .5, CYA was 30, add 1 gal + 2 qt
2:30pm FC 13.5 CC .5
10pm FC 11 CC.5, add 3 qts
10:30pm 15.5 FC

6:30am FC 14 CC .5, add 1 qt
5pm FC 8.5, add 1 gal
9:30pm FC 12 CC 0

6:30am FC 11, add 1 qt
5pm FC 6.5 C 0, add 2 gal
7:30pm add 10 bags (40lbs) salt
9:30pm FC 12.5

6:30am FC 4.5 CC .5, add 2 gal

So for 3 nights the OCLT was 1, 1.5, 1 and then 8!?

The pump has been running nonstop. I did have the filter set to circulate while the salt (Mortons) was added and left it like that overnight and switched it back to filter this morning. I read that salt doesn't interfere with FC, but that and recirculate are the only changes from the 3 passes/near passes of the OCLT to the 8 drop overnight.

There are no ladders in and there are no lights. Should I turn off the pump this evening and stick a tooth brush in the return? That and the skimmer are the only things in the water.

I will continue to SLAM, but wanted to see if there was anything else I should be doing or if anyone had an explanation for the 8 FC drop.



Gold Supporter
LifeTime Supporter
TFP Guide
Jul 3, 2013
Southern OK
Could have been a glitch, testing error (we all make them), could have been something in the salt... just take FC back up to SLAM level and go from there... :)
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