OCLT question

[wal81]

I am planning on doing the overnight chlorine loss test tonight...couple questions.

Background: I opened the pool six days ago. Water is clear. FC is holding ok but not great (I'm raising CYA now to help with that). I'm not SLAMing anymore now, but I want to make sure there are no problems, i.e. algae hiding anywhere and using up the FC.

I know I need to turn off the SWG tonight. Do I have to leave the pump running for the OCLT, or is it ok to turn to the pump off tonight? I've been running the pump continuously since opening to clear the water. I really want to switch to timer mode and only run it 8/9 hours during the day.

Is OCLT better/more reliable with higher FC levels? Right now I'm at 3 FC but I could add some bleach to raise it up before tonight.

FC 3
CC .5
pH 7.3
CYA was 15, raising to 30-40 now
Calc <50
TA 90
Salt 3200

 

[Texas Splash]

We would be glad to help you. But I have to be honest first .. this statement concerns me:

I'm not SLAMing anymore now, but I want to make sure there are no problems, i.e. algae hiding anywhere and using up the FC.

That seems to indicate you really didn't pass the SLAM earlier because passing the OCLT is 1 of 3 parts to passing the SLAM. As such, I would recommend resuming your SLAM FC shock level of at least 12, leave the pump running, and don't stop until you know for sure you've passed the OCLT and other two SLAM requirements. You've come this far, don't let up now.

Also see: Pool School - Perform the Overnight FC Loss Test (OCLT)

To answer a couple questions though:
- Pump doesn't have to be on 24/7 unless you are doing the OCLT in conjunction with (or end stages of) a SLAM
- OCLT does not have to be too high. Minimum of 3 ppm should work. If I were you, I would increase FC to about 6 though only because you seem to be losing a bit more FC that you like after opening-up this season and you really don't want to fall below your minimum at any time. 3 is pretty low. You don't have to change anything on your SWG, just add a little regular bleach to raise the FC tonight just for the OCLT starting number. Hope that helps.

 

[jblizzle]

I would rather see the OCLT done at a minimum FC level of 10ppm. I agree with Pat, that you should likely raise the FC back up to SLAM level, keep running the pump for the night and see what the OCLT tells you.