FC Still dropping - seriously?

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dewdrop519

0
Aug 13, 2010
26
St.Louis, MO
We're trying to get back in the pool after dirty diaper incident Monday evening. Husband immediately added 36oz bleach. The water is crystal clear and has always been. After filling the pool earlier in the year, we added 4 nights of dichlor, per instructions here, and my husband has added some since then, but we never did check CYA. So I checked it and its 0. Have not added dichlor during the shocking process, but definitely will after we're done with all this. The sand pump has been running 24x7 and its been hot and sunny every day. Here's some recent numbers:

Tuesday night at 11:30pm: FC=10, CC=1
We did get some light rain that night. No obvious debris blew into pool.
Wed morning at 5:40 am: FC = 8, CC=.5
I repeated test immediately and got FC=6, CC=1 (??)
Added bleach twice that day to bring it to shock level. I know I probably should have done it more often due to no CYA.
Last addition was about 9pm
Wed night at 11:16 pm: FC = 11, CC=.5
That brings us to this morning!
Thursday at 6am: FC = 9, CC=.5
I repeated test immediately and got FC=7. So I went out and got more water from pool and got FC=6.
The sun is up, but low in the sky, no direct sunlight on the pool.

The fact that I get lower numbers when repeating the test, has me questioning my testing skills??? The water is absolutely sparkling. Could we really need yet another day?
 
The fact that I get lower numbers when repeating the test, has me questioning my testing skills???
Click to expand...
It's not at all uncommon to have all types of testing errors when you first start.....you'll get better and your results are not earthshakingingly off.

If it were my pool, it would be my priority to get CYA in the pool immediately....30-50ppm. You will see your FC consumption slow dramatically.
 
The CC is only .5 this morning, its the overnight FC loss that has me more concerned, though I don't know which numbers to go by. I know we need CYA, but since you can't measure that right away, and it determines your shock level, I figured I shouldn't mess with that now.

Duraleigh, can we just use the calculator to add dichlor to bring it up to 40, and then consider it there, while we continue to shock, even though it may not test at 40 right away?

I really figured we'd be back in the pool by now.
 
Okay, so using the calculator, my target is to get CYA from 0 to 40. Do I just add the recommended 10oz (volume) of dichlor this morning, and then assume its at 40 for purposes of continuing to shock the pool today? With CYA at zero, my shock level is 10, but if its 40, shock level is 16. Should I add dichlor once this morning, then shock to get/keep FC at 16?
When can I check CYA and get an accurate reading.

Thanks everyone for the help.
 
Okay thanks, I just added the dichlor. I'll be checking every hour or so for chlorine, but unfortunately I have to be gone from about 2-5 pm today to take my son to therapy. I'll treat just before we leave and put up the big umbrellas today which shade a good portion of the pool - maybe that will help a little too. My fingers are crossed we're swimming tomorrow. Thanks again. This is such a great site.
 
Well I added 10oz of dichlor at 8am. It's bright and sunny now at 11am. I just checked and the FC is like 32. I think I'm concerned about that.

We added dichlor shortly after we filled the pool (early May?). We've had a lot of rain this year and my husband backwashes a lot, and we do seem to lose all our FC in a day. Anyway if I added too much now, its too late. I'll see what happens through the day. At this point I'm hoping for some FC loss!
 

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With a pool size of 1718ish gallons, 10 oz of dichlor will raise FC by 24 and CYA by 22.
So you can now consider that your CYA for calculating doses is 22.
Keep a record of this number and when/if you add more dichlor adjust the CYA # based on the amount added in the new dose.

I know you want/need to wait for your FC to drop and that is good.
But, when determining how much dichlor to add,
first, determine how much FC you need to increase to shock level (or maintenance target level if you are done shocking).

Example: Your FC is 6 and you want to raise it to 10 using dichlor.
The FC section of PoolCalculator states you will need 1.7oz weight/1.5 oz. volume dichlor to raise FC to 10.
Now, how much CYA was added to the pool in that one dose of dichlor?
Go to "Effects of Adding Chemicals" section (near bottom of poolcalc). It shows adding 1.7 oz dichlor will increase CYA by about 3.7.
So, each time you add dichlor you add the newly added CYA amount to your current level, which you are keeping on a log, right :wink:
Then when the CYA level gets where you want it, 40ish, stop using dichlor and switch to bleach.

Pools sometimes get nuked accidentally (chlorine too high), but just make sure the umbrellas are closed and it gets as much sun exposure as possible.
It should come down considerably today.

Keep us posted :)
 
I would test for CYA this evening because I'm impatient like that. The dichlor was broadcasted? HTH brand? The CYA you added before will show up, and likely today's as well. It'll give you an idea if you can spare the CYA test.
 
Butterfly: Thank you for the great explanation on figuring how much dichlor to add. That was a bit confusing to me on whether to use the current CYA level or the amount it would(should) be after the dose I'm using the calculator add! I'm going to read your 2 middle paragraphs a couple times, LOL. The umbrellas are definitely down and I started keeping a log Tuesday night. I've been using 1800 as the gallons of water. The box the pool came in said 1718, but the estimator at the bottom of the calculator says 2100 for a 12'x2.5' round pool. I figure I'm better off estimating low. I can always add more chemicals based on test results. It's harder to take them out. The pool should get full sun today til around 6:30 or 7 tonight.
 
Frogabog: the dichlor is AquaChem 99% sodium dichloro-s-triazinetrione dihydrate. Please forgive any spelling error - I practically need a magnifying glass to read the canister. The powdery granuals were added the same way I add bleach, slowly poured an arms length out from the return.

If I test for CYA tonight, would it be accurate? I've read on here that it can take up to a week to record. Is that true for the kind I added?

Not sure I understand your last sentence about possibly sparing the CYA test, after suggesting I test for CYA?
 
It might be accurate. I don't know for sure but I do know that I added 20ppm CYA (HTH) at the beginning of the season this year and it disolved in about 3hr's. I tested the next day, and have had consistent readings ever since. HTH dichlor might register similarly. YMMV

At minimum, the CYA you already have in there would register. "Sparing a test" would reference how many CYA tests you have left in your kit and how many times you'll expect to test this season. Impatient testing vs practical testing yano... I have lots left. I was fine with testing impatiently at 24 hours.
 
At 6pm, with full sun all day, and nothing added since the dichlor this morning at 11am, the FC=17.5 and the CC=.5. I'm hoping the nuke level of chlorine today did the trick. Assuming my overnight test is good, what level should I let the FC get down to before its safe to swim tomorrow?

I think I have enough for 2 more CYA tests. I would like to go forward with bleach only for a couple days (while assuming current CYA of 22) and then test for CYA before adding any more dichlor. I'm really scared to get too much because last year we had to drain the pool and start over. So I'd rather go slowly and accurately to get it up to 40ish. Opinions on this are welcome.
 
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