Free Chlorine Loss...

[MikeK2023]

I finished my pool SLAM after two days with a OCLT of .5 and crystal clear water.
Since my wife is convinced that we've got a mustard algae problem (who am I to argue?) I went right into a mustard SLAM after completing it.
My stats at the beginning of the mustard SLAM are as follows:
CYA 40
CH 320
TA 100
pH 7.5
At the beginning of mustard SLAM - recommended FC = 23.8 my FC readings for yesterday and today:

8/29/23 noon - 20.0 added 64 oz 10% Chlorine​

8/29/23 6 PM - 8.5​

8/30/23 6 AM - 8.0 added 224 oz 10% Chlorine​

8/30/23 9 AM - 26​

8/30/23 noon - 15 added 128 oz 10% Chlorine​

8/30/23 2 PM - 12.5 added 160 oz Chlorine​

I mean, I know it's sunny (and pretty warm) here in Tucson but should my FC numbers be dropping so rapidly? Should I continue?

​

11,000 gallon in-ground plaster pool

 

[Bperry]

I finished my pool SLAM after two days with a OCLT of .5 and crystal clear water.
Since my wife is convinced that we've got a mustard algae problem (who am I to argue?) I went right into a mustard SLAM after completing it.
My stats at the beginning of the mustard SLAM are as follows:
CYA 40
CH 320
TA 100
pH 7.5
At the beginning of mustard SLAM - recommended FC = 23.8 my FC readings for yesterday and today:

8/29/23 noon - 20.0 added 64 oz 10% Chlorine​

8/29/23 6 PM - 8.5​

8/30/23 6 AM - 8.0 added 224 oz 10% Chlorine​

8/30/23 9 AM - 26​

8/30/23 noon - 15 added 128 oz 10% Chlorine​

8/30/23 2 PM - 12.5 added 160 oz Chlorine​

I mean, I know it's sunny (and pretty warm) here in Tucson but should my FC numbers be dropping so rapidly? Should I continue?

​

11,000 gallon in-ground plaster pool

If you have any algae at all then you aren’t done with the SLAM. Am I misreading the issue?

 

[MikeK2023]

If you have any algae at all then you aren’t done with the SLAM. Am I misreading the issue?

I'm not seeing any algae and I'm not convinced that we had mustard algae (my wife is). I figured, whatever, I'll go the extra step and treat for mustard even if I don't know for a fact that I have it.

One thing that I forgot to mention - I've done the testing with the recommended Taylor K-2000C kit - not the pool store.

My real question is - are my FC loss numbers whacky or are they normal? After adding 160 oz of 10% chlorine at 2 PM, my FC now sits at 16.0 (up from 12.5 before adding chlorine) and CC at .5 (up from 0 before adding chlorine).

 

[HermanTX]

I would do another Overnight Chlorine Loss Test

For mustard algae you want to increase to 24ppm FC (for 40 ppm CYA) and hold for 24 hours. But as you state, you are losing a lot of FC rapidly.

 

[Bperry]

I'm not seeing any algae and I'm not convinced that we had mustard algae (my wife is). I figured, whatever, I'll go the extra step and treat for mustard even if I don't know for a fact that I have it.

One thing that I forgot to mention - I've done the testing with the recommended Taylor K-2000C kit - not the pool store.

My real question is - are my FC loss numbers whacky or are they normal? After adding 160 oz of 10% chlorine at 2 PM, my FC now sits at 16.0 (up from 12.5 before adding chlorine) and CC at .5 (up from 0 before adding chlorine).

You can tell her that mustard algae is extremely rare and you probably have normal algae. Tons of people come here thinking they have it and end having plain boring algae. (Or don’t tell her that…)

 

[Brian PacNW]

(Or don’t tell her that…)