FC too low

Jump to latest Follow Reply
B

brainfreeze

Member
Jun 11, 2024
12
Edison, New jersey
Pool Size
10000
Surface
Vinyl
Chlorine
Liquid Chlorine
hi all,
New pool owner, had a pool guy open it for us. The water is clear (maybe not crystal clear). FC on test strip doesnt register anything at all.
tested with TF-100 test kit, FC was very low 2 days ago (1.5). CC was 5. pH was high as well (7.9).
Got it tested at a pool store as well, they also said the same thing. i started the SLAM process, added 4 gallons of liquid chlorine Sunday night. Monday morning, FC was 3, CC was 3.5. Added another gallon chlorine.
Monday evening, the FC was 5, CC down to 2.5. Added 2 gallons more, to bring FC up to 8 or so. Tested today morning, FC was back down to 3 and CC 3.5.
per the pool store test, CYA was 40. However, the TF-100 CYA test doesnt turn much cloudy at all, indicating i have no CYA?

Since my water is clear, do i really need to bring FC up to 16 ppm?
Do i need to add muriatic acid first before trying to bring FC up?
what's up with CYA? i dont want to risk getting CYA too high.

Pump has been running 24*7 since sunday as well.

Thank you all again for your help. This is a wonderful community and i am excited to learn more about pool chemistry.
 

Attachments

  • IMG_5207.jpg
    IMG_5207.jpg
    209.2 KB · Views: 14
brainfreeze said:
hi all,
New pool owner, had a pool guy open it for us. The water is clear (maybe not crystal clear). FC on test strip doesnt register anything at all.
tested with TF-100 test kit, FC was very low 2 days ago (1.5). CC was 5. pH was high as well (7.9).
Got it tested at a pool store as well, they also said the same thing. i started the SLAM process, added 4 gallons of liquid chlorine Sunday night. Monday morning, FC was 3, CC was 3.5. Added another gallon chlorine.
Monday evening, the FC was 5, CC down to 2.5. Added 2 gallons more, to bring FC up to 8 or so. Tested today morning, FC was back down to 3 and CC 3.5.
per the pool store test, CYA was 40. However, the TF-100 CYA test doesnt turn much cloudy at all, indicating i have no CYA?

Since my water is clear, do i really need to bring FC up to 16 ppm?
Do i need to add muriatic acid first before trying to bring FC up?
what's up with CYA? i dont want to risk getting CYA too high.

Pump has been running 24*7 since sunday as well.

Thank you all again for your help. This is a wonderful community and i am excited to learn more about pool chemistry.
Click to expand...
One problem is the pool store, do not waste time with them. They are really bad at testing

If your test kit says the CYA is low, add enough to increase it 10ppm and check it again in a couple days.

Your CC test process sounds suspect unless youve been using non-chlorine shock. Are you confident on that? Using 10ml of water, right? Once you do the FC test, you add 5 drops of r-003 and if it turns pink at all, that means there is some amount of CC. Then immediately start adding drops of r-0871 again to make it turn clear. Once it turns clear, divide the number of drops by 2 and thats youre CC result. If you let the sample sit for a bit, it might turn pink again but dont add any more drops.
 
Bperry said:
One problem is the pool store, do not waste time with them. They are really bad at testing

If your test kit says the CYA is low, add enough to increase it 10ppm and check it again in a couple days.

Your CC test process sounds suspect unless youve been using non-chlorine shock. Are you confident on that? Using 10ml of water, right? Once you do the FC test, you add 5 drops of r-003 and if it turns pink at all, that means there is some amount of CC. Then immediately start adding drops of r-0871 again to make it turn clear. Once it turns clear, divide the number of drops by 2 and thats youre CC result. If you let the sample sit for a bit, it might turn pink again but dont add any more drops.
Click to expand...
yes i am running the CC test the way you have described. My sample was turning pink back very quickly after the FC test, so i upped the qty of the 870 powder a tad bit. i take the reading as soon as it turns clear.
 
brainfreeze said:
yes i am running the CC test the way you have described. My sample was turning pink back very quickly after the FC test, so i upped the qty of the 870 powder a tad bit. i take the reading as soon as it turns clear.
Click to expand...
Thats kinda weird. You might clean the vial with some alcohol and try it again.
 
Don't waste your time with teststrips or pool store testing.
Use your TF-100 and trust your own testing.
 
Last edited:
  • Like
Reactions: Darin
Bperry said:
Thats kinda weird. You might clean the vial with some alcohol and try it again.
Click to expand...
i was going through some other threads on this forum and came across one which mentioned that trichlor tablets invalidate the FC test. the pool guy added a bunch of pucks in the chlorine floater thingy and i still have a bunch left in there.
is that what's causing the test numbers to be off? what should i do?
 
brainfreeze said:
i was going through some other threads on this forum and came across one which mentioned that trichlor tablets invalidate the FC test. the pool guy added a bunch of pucks in the chlorine floater thingy and i still have a bunch left in there.
is that what's causing the test numbers to be off? what should i do?
Click to expand...
FC over 10 invalidates the pH test.

Your CC number is high.

Pull the tab floater and do an Overnight Chlorine Loss Test tonight to see if a SLAM Process is needed.
 
brainfreeze said:
that trichlor tablets invalidate the FC test.
Click to expand...
They do not. Maybe confused that with the pH test when the chlorine is too high as mentioned above. Sounds like maybe your chlorine has been too low for a while and you’ve algae starting to brew, although you can’t see it yet. Do the tests mentioned above and see what that tells you
 
Bperry said:
They do not. Maybe confused that with the pH test when the chlorine is too high as mentioned above. Sounds like maybe your chlorine has been too low for a while and you’ve algae starting to brew, although you can’t see it yet. Do the tests mentioned above and see what that tells you
Click to expand...
Thank you! My FC is 3 right now, I will test again tomorrow morning.
Do I need to increase my pH and CYA as well? I can do that tomorrow morning after the OCLT.
 

Enjoying this content?

Support TFP with a donation.

Give Support
brainfreeze said:
Hi! I did the chlorine test this morning and FC is 2 ppm , CC at 3 ppm.

do I need to SLAM still or just add enough chlorine to keep FC at 4 or 5?
Click to expand...
Thr chlorine test using the powder and drops? The CC being so high makes it sound like your using the yellow OTO test and getting TC instead of CC. Unless you have a green swamp then really high CC makes sense.
 
brainfreeze said:
yes i did the test using powder and drops.
Click to expand...
Sorry, just wanting to be sure. Once you get your FC result, you are adding 5 drops of the R-0003 and that turns the sample pink again. Then adding 7 drops of the r-0871 makes it go clear again? If so, then yea you have a high CC of 3.5ppm
 
  • Like
Reactions: proavia
There are two different testing times to the Overnight Chlorine Loss Test.
First, you test after dark (at least 15-30 minutes after the last chlorine add) and record the FC
Sedond, you tewt in the morning before sun is on the pool and record that FC.
Then compare the two tests.
Of course, pump needs to be running the entire time.
 
proavia said:
There are two different testing times to the Overnight Chlorine Loss Test.
First, you test after dark (at least 15-30 minutes after the last chlorine add) and record the FC
Sedond, you tewt in the morning before sun is on the pool and record that FC.
Then compare the two tests.
Of course, pump needs to be running the entire time.
Click to expand...
But take all the pucks out a 1/2 hr or more earlier, so they don't keep adding Cl overnight....
 
  • Like
Reactions: Bperry
brainfreeze said:
So I have a silly question. When I take the pucks out, how do I store it so as not to cause anyone harm from chlorine gas?
Click to expand...
Set them out in the sun to fully dry. Then put in a plastic ziplock type bag and put back in the bucket they came in.
Any off-gassing while they are drying shouldn't be an issue if you place them in a well ventilated area.
 

Enjoying this content?

Support TFP with a donation.

Give Support
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply