Why aren't my cc's dropping??

[OneMom]

Hi All:

We started this pool season with a green swamp. Found this forum & realized our CYA was well over 150. Have been using the "Best Guess" chart, drained some water, raised chlorine to "shock" levels appropriate to our CYA, etc. We use Taylor's FAS/DPD kit.

Anyway, our pool LOOKS beautiful. However, we have NEVER had a CC reading of zero. When we test the CC, the water always turns a very light pink. It takes one drop of solution to then make the water clear...therefore giving us a reading of approximately .5 CC.

So, for the last six nights, we've tested the chlorine & gotten FC levels ranging from 18 to 20 ppm. Each night the CC's have been at .5 ppm. Each night we've added chlorine to bring the FC to at least 20 ppm. Should we start testing each morning also? If the FC is below 20 should we add more chlorine immediately in the morning? Between the sun, heat & CC reading we are losing 5ppm each day. Here's tonight's numbers:

CYA 70
FC 20
CC .5
PH 7.6
TA 90

This is driving us crazy!! We have added more than 8 gallons of 15% chlorine in the last six days. (To save you time doing the math: 1 gallon adds 5ppm to our pool.)* We have kept the filter on 24/7 for around two weeks now. Should we just keep at this, knowing that eventually all of the chlorimates will be gone & we'll be able to let our FC drift down to 5-10ppm?

Is it okay for the kids to swim in FC levels between 15 and 25?

Thanks!!

We have: 30,000* gal, vinyl IG with sand filter. We live in Milwaukee, WI area.

 

[Buggsw]

Yes, you need to keep your chlorine levels up to shock level day and night until the level stays overnight. Once it stays high overnight, you let it drop into the appropriate range for swimming.

 

[mbar]

It happened to me this year too I opened to a green swamp, and had to keep my pool at shock levels for at least 2 weeks, maybe closer to 3. I also had beautiful clear water, with cc showing 0 to .5. I kept adding bleach to keep shock levels until it was 20ppms (tested after sun went down) till morning when the pool was still in shade. Even though it only dropped 2 ppms sometimes, it did eventually not drop at all. I don't know if it was just from the "swamp", I think it was also from so much pollen dropping this year. It is only in the last week that the pollen has not been really heavy on the skimmer sock. So I would suggest keeping the bleach levels at shock - especially at night.

 

[OneMom]

Is it safe to swim with the FC levels so high? I know it will fade our swim suits, but we can live with that.

 

[Buggsw]

I wouldn't swim in it until the level was back down to under 10ppm, myself.

 

[duraleigh]

Onemom,

It is not uncommon for pools to test at .5 CC's. That's not a huge deal and, as long as your water looks nice, I would ignore it unless it goes higher.

Meanwhile, go swimming....my bet is you see no fading of clothing. Your washing machine, with a cup of clorox added, brings the chlorine in the wash up over 300ppm. (somebody double check that math....I did it twice assuming a 12 gal washer capacity)

 

[mbar]

I have gone swimming in my pool with fc of 20, and am alive and well :?: :-D No, really it is ok to swim in those levels - some may want to wear an old bathing suit - but I never had one fade. It is always a good idea to rinse a bathing suit in fresh water after swimming anyway.

 

[Poseidon]

OneMoM,
If you are using the "1 drop = .5 ppm" test, your CC could very well be below .5 ppm. Possibly even .1 ppm.
Wouldn't worry about it.

 

[OneMom]

Thanks so much for the replies. I do feel a little confused though. Some of you feel that we should keep FC at shock level until the CC test is zero. Some of you feel the .5 reading (or possibly less - we only need one drop to get the pink out) is no big deal & we could stop keeping the FC at shock level.

Yikes! Between losing 5 ppm FC a day and NEVER having a zero CC reading this season, I guess we'll keep to shock levels until the CC is zero.

I also appreciate the information that the majority of you feel it's safe to swim in the pool, even though the FC is high.

Thank you all for taking the time to answer my questions!! I love this forum!!!

 

[chem geek]

Technically, your pool with 20 ppm FC and 70 ppm CYA has roughly the same amount of disinfecting chlorine (hypochlorous acid) in it as a pool with 0.4 ppm FC and no CYA. Many indoor pools have 1-2 ppm FC (or sometimes more) with no CYA so have more disinfecting chlorine than your pool.

So the rate of degradation of swimsuits (and skin, etc.) will actually be higher in most indoor pools than in your pool. That is, when immersed in the water. The difference is that when you get out of the water, there is a much larger reserve of chlorine in the 20 ppm FC so though it will react slowly, it will keep reacting longer (i.e. won't get used up as quickly) unless you rinse your swimsuit (and skin) after getting out of the pool. Also, if you were to swallow pool water, then the 20 ppm FC is more harmful since it contains more chlorine and will tend to react quickly in your body -- mostly in your mouth when it hits saliva. A single exposure from drinking this isn't terrible -- prolonged exposure could be.

As for the persistent CC, I would be less concerned with that then with chlorine usage overnight. Such usage indicates something in the pool that chlorine is still combining with and that needs to be removed through shocking, sunlight, filtration, or physical removal (e.g. leaves). Usually, usage of chlorine overnight along with some CCs typically means you've still got some sort of nascent algae. CCs without overnight chlorine usage just means you've got some organics with attached chlorine that aren't breaking down readily even in sunlight. They are not harmful and in fact you've got all sorts of other organics in your pool that chlorine doesn't readily combine with or break down and aren't measured on the CC test. It's really only ammonia, algae, and bacteria/viruses/protozoa that you want to remove -- the ammonia because the CCs smell and some are carcinogenic. Interestingly, I read something recently that said that urea is resistant to breakdown from sunlight and doesn't combine readily with chlorine so isn't broken down by that either nor registering in CCs, but that's still speculation at this point until I can get some further verification on that.

Richard