FC test troubleshooting - am I crazy??

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A

Aggie_aloha

Member
Apr 3, 2018
18
Rowlett, TX
Pool Size
30000
Surface
Plaster
Chlorine
Liquid Chlorine
Specs: in ground 30k freshwater pool. No CYA, pH7.5, TA60, everything else within range per pool match app, except FC. Not adding CYA until I'm sure no more algae.

I've been slamming my pool bc of algae (pump/filter issue that is now resolved). Water is now clear and has been for a few days but FC keeps coming in at zero when I test at night so I slam more. It's hot here in Texas so I assumed it gets burned during the day (but I've never experienced it this bad). Figured I still had algae somewhere. I got suspicious after week 2 of slamming (costs a lot for 3 bottles a day) and threw out my old fas dpd and ordered a new one. Tested with new Taylor powder and still clear. I added at least 6 full scoops. Nothing. I thought I was crazy so I tested it with tap and some chlorine. Still nothing. Am I crazy??
 
Aggie_aloha said:
Specs: in ground 30k freshwater pool. No CYA, pH7.5, TA60, everything else within range per pool match app, except FC. Not adding CYA until I'm sure no more algae.

I've been slamming my pool bc of algae (pump/filter issue that is now resolved). Water is now clear and has been for a few days but FC keeps coming in at zero when I test at night so I slam more. It's hot here in Texas so I assumed it gets burned during the day (but I've never experienced it this bad). Figured I still had algae somewhere. I got suspicious after week 2 of slamming (costs a lot for 3 bottles a day) and threw out my old fas dpd and ordered a new one. Tested with new Taylor powder and still clear. I added at least 6 full scoops. Nothing. I thought I was crazy so I tested it with tap and some chlorine. Still nothing. Am I crazy??
Click to expand...

So your testing at night and FC is 0? Without CYA in the beginning of summer it isn’t crazy that the sun would burn of 10 FC (assuming 10% at 30k pool and 3 gallons) without CYA. High yes, but not crazy.

Have you done an overnight loss test? Dump the same chlorine in after sunset, test 30 minutes later, then test before sunrise. If you have less than 1ppm loss your ok, if not something is living in there.

I’m pretty sure SLAM procedure recommends a minimum CYA for this reason. Between sun and algae you’d probably have to add so frequently it makes no sense.

Others will weigh in but if you don’t pass the OCLT I’d bring up CYA to 20 and keep going until you pass.
 
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I'm not crazy. Just retested an hour after adding 3 gallons and FC at 10. I add in the evening at 8:30p, but don't have a chance to test in the morning before work. Now that the weekend is here, I'll test in the morning. Never had algae this far into summer so didn't realize the immediate burn. I've always had FC in the pool when I test in the summer evening but that was with CYA.
 
Aggie_aloha said:
I'm not crazy. Just retested an hour after adding 3 gallons and FC at 10. I add in the evening at 8:30p, but don't have a chance to test in the morning before work. Now that the weekend is here, I'll test in the morning. Never had algae this far into summer so didn't realize the immediate burn. I've always had FC in the pool when I test in the summer evening but that was with CYA.
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The chlorine will burn off in 30 minutes without CYA. Read the SLAM process again…
 
PoolStored said:
Granular stabilizer is cheaper and easier. Add it using the sock method. If you do use the liquid, use each entire gallon, and make sure that you rinse the bottle multiple times to get ALL of it out.
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Understood. I have granular but it takes a long time to dissolve for me. Liquid is just faster to get it going so that I can properly slam and I am not spending hundreds a week for chlorine.
 

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Aggie_aloha said:
Understood. I have granular but it takes a long time to dissolve for me. Liquid is just faster to get it going so that I can properly slam and I am not spending hundreds a week for chlorine.
Click to expand...
It should dissolve quickly. Put it in a sock and hang in front of a return (carrot on stick style). After about 1/2 hour, start squeezing, shouldn't take long. Or put the sock in the skimmer (make sure it is tied off). Squeeze a bunch every couple hours. If you want to spend the money, OK by me, but you must rinse, rinse, rinse the jug to get it all out.

Target adding 30ppm CYA. Start your slam with FC of 10. When the granular is dissolved, use FC 12 for your SLAM target.
 
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Aggie_aloha said:
Understood. I have granular but it takes a long time to dissolve for me. Liquid is just faster to get it going so that I can properly slam and I am not spending hundreds a week for chlorine.
Click to expand...
It doesn’t need to dissolve quickly, once it starts soaking just assume it’s in.

If you add two scoops (or even one!) and the FAS-DPD test sample doesn’t turn pink at all that means you have zero chlorine, so don’t add any more powder.
 
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