TF-100 Kit Arrived Today - I think I'm losing FC nightly

dakstn

Member
May 25, 2020
12
Western Pennsylvania
I opened my pool over a week ago and the water has been clear since that day, however, I haven't been able to keep the chlorine level up (based on the basic Taylor OTO kit and store-bought test strips). I ordered the TF-100 kit and have been adding liquid chlorine (12.5%) daily to keep chlorine in the pool until the kit arrived. The kit arrived today and my test results are below.

TF-100 RESULTS
FC: 1
CC: 2.5
TC: 3.5
CH: 450
TA: 240
CYA: 50
pH: 7.8

I will perform the OCLT tonight with the expectation that I will lose more than 1.0 ppm FC. If so, I'll start the SLAM process.

My questions at this point are:
Is there an article or post with the SLAM steps outlined (assuming my OCLT results show I need to SLAM)?
Are there any other numbers in my TF-100 test results that stand out and should be addressed?

Thanks in advance for any help.
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,633
San Dimas, CA (LA County)
Verify your test method.

Add powder. It turns pink. Coiunt drops until it goes clear. That's FC. Right then. Don't wait ten minutes. where it turns pink again. The first time it goes clear is the FC. Then add the 5 drops. If it doesn't turn pink again immediately, no CC. If it does, add drops until it turns clear again the first time. That's the CC. If it goes pink a few minutes later, it means nothing.

Then if you still have high CC, you need to ask if you added any "nonchlorine shock" to the pool in the last month, because the MPS in it will falsely read as CC.

If you still are convinced you have 2.5 CC, then SLAM Process


 

dakstn

Member
May 25, 2020
12
Western Pennsylvania
Verify your test method.

Add powder. It turns pink. Coiunt drops until it goes clear. That's FC. Right then. Don't wait ten minutes. where it turns pink again. The first time it goes clear is the FC. Then add the 5 drops. If it doesn't turn pink again immediately, no CC. If it does, add drops until it turns clear again the first time. That's the CC. If it goes pink a few minutes later, it means nothing.

Then if you still have high CC, you need to ask if you added any "nonchlorine shock" to the pool in the last month, because the MPS in it will falsely read as CC.

If you still are convinced you have 2.5 CC, then SLAM Process


Thanks for that information. I just re-tested the chlorine numbers twice and got these results both times:
FC: 1
CC: 2

Also, I did add 5 lbs of "nonchlorine shock" to the pool about 8 days ago.
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,633
San Dimas, CA (LA County)
Thanks for that information. I just re-tested the chlorine numbers twice and got these results both times:
FC: 1
CC: 2

Also, I did add 5 lbs of "nonchlorine shock" to the pool about 8 days ago.
If it contained Potassium Monopersulfate, there's your CC reading. It eventually goes away. Not sure how long it lingers. Trying to SLAM it away with bleach probably won't help. If the water is clear and the walls aren't slimy, just raise your FC to normal levels and go swimming.
 

dakstn

Member
May 25, 2020
12
Western Pennsylvania
If it contained Potassium Monopersulfate, there's your CC reading. It eventually goes away. Not sure how long it lingers. Trying to SLAM it away with bleach probably won't help. If the water is clear and the walls aren't slimy, just raise your FC to normal levels and go swimming.
You're right, I used Clorox Shock Oxidizer which has Potassium Monopersulfate as the main ingredient. The water is crystal clear and walls aren't slimy... so, we'll swim today, but I am going to try the OCLT test tonight because over the past few days I've added the liquid chlorine at night and it was mostly gone by morning. I assume if the OCLT shows a loss of more than 1.0 ppm FC overnight I should SLAM regardless of the CC reading?

Thanks again.
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,633
San Dimas, CA (LA County)
You're right, I used Clorox Shock Oxidizer which has Potassium Monopersulfate as the main ingredient. The water is crystal clear and walls aren't slimy... so, we'll swim today, but I am going to try the OCLT test tonight because over the past few days I've added the liquid chlorine at night and it was mostly gone by morning. I assume if the OCLT shows a loss of more than 1.0 ppm FC overnight I should SLAM regardless of the CC reading?

Thanks again.
Yes. Precisely.
 

tillmac62

Well-known member
Sep 30, 2019
73
Gaffney, SC, United States
MPS will register as CC until it is "consumed" by oxidizing something. Since you added it 8 days ago, your pool has consumed it since "because over the past few days I've added the liquid chlorine at night and it was mostly gone by morning".
 

dakstn

Member
May 25, 2020
12
Western Pennsylvania
Wow. You got something goin' on in there. That's two or three days' worth of losses without sun!

I don’t understand it either. Never had this issue in 10+ seasons. If I simply kept adding a gallon of liquid chlorine every night, would the algae (or whatever is eating it all up) eventually be destroyed/oxidized? It would maybe just take a lot longer than SLAMing? Regardless, I’ll SLAM... I am just curious.
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,633
San Dimas, CA (LA County)
I don’t understand it either. Never had this issue in 10+ seasons. If I simply kept adding a gallon of liquid chlorine every night, would the algae (or whatever is eating it all up) eventually be destroyed/oxidized? It would maybe just take a lot longer than SLAMing? Regardless, I’ll SLAM... I am just curious.
Algae can grow really fast. So you kill half at night and it doubles the next day. Stalemate. You have to kill it faster than it can grow. Much faster. You have to SLAM it.

Also consider that the algae you're killing first is the weaker strains, so the longer you draw things out, the harder it gets to kill. Sort of like the worries about antibiotic-resistant bacteria. You're growing a super race of algae!
 

dakstn

Member
May 25, 2020
12
Western Pennsylvania
Algae can grow really fast. So you kill half at night and it doubles the next day. Stalemate. You have to kill it faster than it can grow. Much faster. You have to SLAM it.

Also consider that the algae you're killing first is the weaker strains, so the longer you draw things out, the harder it gets to kill. Sort of like the worries about antibiotic-resistant bacteria. You're growing a super race of algae!
Gotcha, that makes sense. I’ll get the FC level up to SLAM, continue to swim and enjoy the water, and will post back with updates. Thx.
 

dakstn

Member
May 25, 2020
12
Western Pennsylvania
Added 2 gallons of liquid chlorine this morning to start SLAM. Just tested and my FC level is currently up to 20 per recommended my CYA of 50. I assume it's normal that the CC is super low right now? When I added the 5 drops to turn it back to pink, it was pretty much still clear and one drop made it absolutely clear. So, I'd say my CC right now is between 0 and 0.5. Also, I know I've asked already, but just confirming... it's OK to swim at FC 20 ppm, right? It feels like adding 2 gallons of liquid chlorine should not be OK to swim :)
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,633
San Dimas, CA (LA County)
Added 2 gallons of liquid chlorine this morning to start SLAM. Just tested and my FC level is currently up to 20 per recommended my CYA of 50. I assume it's normal that the CC is super low right now? When I added the 5 drops to turn it back to pink, it was pretty much still clear and one drop made it absolutely clear. So, I'd say my CC right now is between 0 and 0.5. Also, I know I've asked already, but just confirming... it's OK to swim at FC 20 ppm, right? It feels like adding 2 gallons of liquid chlorine should not be OK to swim :)
Yep.