Is there really Combined Chlorine in my pool all the time?

[owkaye]

I bought the Taylor FAS-DPD Chlorine Test kit (K-1515-A) because I had all the other tests I need. I've been using it with 10 ml pool water samples so I am getting readings of 0.5 precision. The FC portion of these tests seem reasonable and are likely correct every time, but I'm not sure about the CC portion of my tests:

Every time I check for CC I get a positive result of 0.5 ppm. Not once have I tested and found 0 ppm CC, yet I thought it was common for residential pools to have 0 ppm CC most of the time.

Are my CC test results unusual?
Or is this a normal / expected result for every CC test?

 

[Donldson]

Some pools do seem to always have minor CC issues. Does your pool get a bunch of shade or tree debris falling in to the pool? If you could, please post up your FC and CYA results too. That could offer some insight as well.

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[ewkearns]

Most people will disagree with me, but I don't think the 10 mL test is nearly accurate enough. Try once with 25 mL and see what you get. If it really is staying at .5 ppm, you might have something trying to get started...

 

[ping]

Owkaye, when I read your signature it makes me believe that you have a lot of debris in the pool which will lead to CC's. What is your FC target and how much is lost everyday? Post the CYA level also.

 

[JoyfulNoise]

Most people will disagree with me, but I don't think the 10 mL test is nearly accurate enough. Try once with 25 mL and see what you get. If it really is staying at .5 ppm, you might have something trying to get started...

Agreed. You should run the 25mL test. When I test with 25mL I only truly get 0ppm CCs maybe half the time. Typically I get just the faintest bit of pink (I have to strain and squint to see it) with the addition of the R-0003. It immediately goes clear with a single drop of titrant. I often call that <0.2ppm. With a 10mL sample size, you may have 0.5ppm or 0.4ppm or 0.3ppm, etc. There's just not enough precision to know exactly. If you are testing your water daily, then I would suggest you do the more precise 25mL sample at least once or twice per week.


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[Richard320]

I've gone through periods where I show CC at every test for weeks and then somehow it goes away again for a while.

It could be something as simple as debris in the skimmer or pump strainer or superfine stuff in the filter. Just because it's not in plain sight doesn't mean it's not there. Your chlorine could be trying to oxidize some organic debris that isn't algae.

 

[owkaye]

Some pools do seem to always have minor CC issues.

I think this describes my pool, assuming the test results are accurate.

Does your pool get a bunch of shade or tree debris falling in to the pool?

Yes. This pool is 70% shaded all day every day, and quite a bit of "stuff" seems to jump off the overhead Live Oak tree and land in the pool, mostly ferns and leaves and small bugs and such. I skim it out manually a couple times a day but there is always something in there the next time I go out and look at it. I plan to build a frame over the pool and stretch a tarp over it to keep most of the tree stuff out, but I won't be able to build it until this weekend at the earliest.

If you could, please post up your FC and CYA results too.

TA = 70-80 ppm
CYA = 40-50 ppm
FC = 6.0 ppm
CC = 0.5 ppm
Borates = 40 ppm (based on poolmath)

Try once with 25 mL and see what you get. If it really is staying at .5 ppm, you might have something trying to get started.

Will do.

You may have a lot of debris in the pool which will lead to CC's. What is your FC target and how much is lost everyday?

My target range for FC is 5.0 - 7.0 ppm. My plan is to add bleach the moment my FC drops to 5.0 -- enough to bring it up to 7.0 again.

I don't know how much FC is lost every day because I have not been monitoring it. Mostly for the past 2-3 weeks I have been working to bring my TA down and my CYA up to the levels suggested for the addition of borates. During this period my FC was at shock level a couple times because I added more dichlor than I should have. But now that my CYA level is on target and I have added most of my borates, I will start monitoring my daily FC loss.

Typically I get just the faintest bit of pink with the addition of the R-0003. It immediately goes clear with a single drop of titrant.

This is precisely what happens every time I have done the CC test with 10ml. So based on the suggestions here I'm going to run the CC test using 25 ml just to see what I get.

I've gone through periods where I show CC at every test for weeks and then somehow it goes away again for a while..

So seeing low CC numbers is not unusual I guess. Thanks Richard.

It could be something as simple as debris in the skimmer or pump strainer or superfine stuff in the filter.

Or stuff from the tree!

Your chlorine could be trying to oxidize some organic debris that isn't algae.

I have never seen any indication of algae, but maybe the consistent (yet not overwhelming) "raining down" of stuff from the tree will always keep my CC higher than zero ... at least until I get my canopy / cover built.

 

[JoyfulNoise]

Sounds like your problems are shade and debris. The debris part is obvious, "junk" = oxidation by chlorine = CCs.

The shade is also a minor issue to because UV from sunlight is a great way to help destroy CCs. So if you do build your canopy, try to leave it off during the sunny times on your pool water. You really want the good UV rays from the sun to help you out.


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[ping]

I believe the CC's are the result of the amount of shade on the pool along with the amount of debris in the pool. As long as you follow the FC/CYA chart the pool should do fine and you can ignore the .5 CC result. Do not stop testing for CC's as that is a good indicator of trouble if it rises above .5 in your pool.

 

[Donldson]

In your case I honestly wouldn't worry a bit about this. If the water is clear and your daily FC loss is only 2 then it doesn't sound like a problem worth dealing with unless you are noticing problems associated with CC.

I am going to disagree with the necessity of doing the 25ml test in your specific case. Since you are seeing normal and predictable FC loss during the day and everything looks good otherwise then I wouldn't really worry about it. You have a pretty good indication of the cause of the CC reading and it is still well within spec. If you ever get more than 0.5 CC or find your FC loss to be rising then you will know a problem is brewing.

 

[borjis]

I get that as well sometimes weeks of .5 cc then nothing at all.

If I leave the solar cover on for a week I might not lose any FC for 2-3 days in a row.

not worried about it.

 

[buzzard302]

I had a period where I was getting false CC readings. It extended my SLAM for days and days. Long story short, my test tube has been stored outside for a long period of time. The test tube itself had something in it that was reacting with my test sample and giving CC readings.

Make sure your test equipment is clean first off. I just let chlorinated water stay full in the sample tube for an hour and the tube was sanitized. After that, no more CC readings.

 

[owkaye]

Thanks for the recent posts everyone. It looks like I have valid reasons for seeing an 0.5 ppm CC value every time I test. I did not realize it takes sunshine to eliminate CC so I will leave the pool uncovered most days from now on.

I ran the FAS-DPD tests a couple hours ago using 0.2 precision:

FC = 3.4 (17 drops of reagent; I could use a lot of this stuff if I always ran my tests at 0.2 precision!)
CC = 0.4 (but the pink was virtually gone with the first drop of reagent, so maybe this should be 0.3 ppm?)

Then I added enough bleach to bring my FC up to 6.7 according to poolmath. An hour later I re-tested using 0.5 precision but my FC had only reached 6.0 so I added a little more bleach. I'm guessing it's about 7.0 ppm now, but I won't test again until tomorrow since I know it is high enough for a day or two.

Today I made a skimmer out of a 5-gallon Walmart bucket and two plumbing fittings from Lowe's. My filter pump is bigger than the one that came with this pool but it is still too weak for my liking. It simply does not have the power to create as much skimmer suction as I want. Nevertheless the skimmer does seem to be slowly collecting most of the stuff that falls into the pool. I hope it's effective enough that I won't have to skim manually several times a day any more.

 

[ThomasG]

I have lots of live oaks and palms around my pool and often have ~0.5 CC. About half the pool gets sun, and the deep end is shaded. Not worried about it, but February and March will be a challenge with leaf and pollen fall.

 

[Agent99]

Valley Oak Tree 'bout a 100 years old in my backyard and it constantly rains stuff 365-52-24-7 into my pool. That and it is a Holiday Inn for squirrels.

Oak has tannins/tannic acid and I've noticed the shells around the acorns will start to produce a noticeable brown spot if they sit in the bottom of the pool or spa and don't move for a while. Now when this first happened on my brand new (28 days since initial fill-up) Blue Granite Pebble Sheen finish, I nearly had a heart-attack and immediately wished I had opted for a darker pool finish. I would go at the stain with a scrub brush and it only seemed to marginally help.

However, the next day dawned and low and behold the stain(s) were gone! This has happened a lot since and thankfully I know the stain will disappear soon if I remove the source ASAP. Anyway, my CCs always show 0.5 as well and now I think I have the source. What I'm wondering is if the chlorine is attacking the stain and removing it? Kind of like bleach attacks stains on clothes. Plausible?

 

[JoyfulNoise]

Valley Oak Tree 'bout a 100 years old in my backyard and it constantly rains stuff 365-52-24-7 into my pool. That and it is a Holiday Inn for squirrels.

Oak has tannins/tannic acid and I've noticed the shells around the acorns will start to produce a noticeable brown spot if they sit in the bottom of the pool or spa and don't move for a while. Now when this first happened on my brand new (28 days since initial fill-up) Blue Granite Pebble Sheen finish, I nearly had a heart-attack and immediately wished I had opted for a darker pool finish. I would go at the stain with a scrub brush and it only seemed to marginally help.

However, the next day dawned and low and behold the stain(s) were gone! This has happened a lot since and thankfully I know the stain will disappear soon if I remove the source ASAP. Anyway, my CCs always show 0.5 as well and now I think I have the source. What I'm wondering is if the chlorine is attacking the stain and removing it? Kind of like bleach attacks stains on clothes. Plausible?

Yes. Fresh tannin stains are oxidized by hypochlorous acid but very slowly. And you are absolutely correct that you can't let oak debris sit around too long as the tannin stains get harder to remove with age.


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[Agent99]

Yes. Fresh tannin stains are oxidized by hypochlorous acid but very slowly. And you are absolutely correct that you can't let oak debris sit around too long as the tannin stains get harder to remove with age.

Perhaps it because I tend to my pool every evening (and some mornings) to remove such things but the brown spot seems to dissipate within 24 hours.

This is also why I need to install a pool cover when I leave for a period of time...like vacations. We love this tree but it IS a lot of work dealing with it!!

 

[jojoman]

Lots of tree junk falls into my pool, esp. with the high winds we are having this year. .5 CC's is pretty much the norm for me but i haven't seen it go higher yet.