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Thread: Where is my FC going ?

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    Where is my FC going ?

    This looks like an awesome site and I'm glad I found it. I've had my algae problems off and on over the years which I usually managed to deal with most effectively with copper algecide (I know that is a bad word here). However, the last 2 years I've had trouble with reading any chlorine on my simple DPD test kit. Although my pool store has been in business as long as I have had the pool, they haven't been too helpful lately. Last year they told me it was because I had excessive phosphates in the water and sold me that expensive phosphate remover. I actually did get a free chlorine reading after that for awhile.

    A few weeks ago, my pool was cloudy and I shocked it with my usual 2 lbs. of Dichlor (I had had a heavy load for a few days). When that didn't work I tried 4 lbs.. After a while I finally went to the pool store and they told me to add a gallon of 12 % bleach and check for FC after 12 hours. I went through 4 bottles and still no FC. Then I went to their other store where they sold 10% bleach for more than the 12% (ouch) and went through another 4 bottles and still no FC. However my pool water had cleared up and is still clear. So a week ago last Wednesday I went on the internet and found this site. I went through pool school and have read many of the posts, especially those with CYA of 100.

    So last Thursday I went to Sam's and bought some bleach and using the calculator added 7 jugs of 182 oz. bleach. I also ordered the TR-100 test kit which as it turns out comes from about 20 miles up the road and I had it the next day. In retrospect I wish I had waited until I got the kit and learned a bit more. So here is what I have going on the last few days.

    On 8/7 in the PM I had:
    FC 5, CC .5, TC 5.5, PH 7, T/A 100, CH 220 and CYA 100?

    Other than the chlorine numbers the rest of it agreed with the pool store's numbers. As I recall I did a chlorine drop test the next morning and FC was at 4. I can't find the piece of paper I wrote down my 8/8 readings. I wanted to start keeping the data in a spreadsheet sionce the log with the test fkit would soon be filled up. I also added the rest of the PH+ stuff I had and my PH is now up to 7.2 Starting on the 9th I had.

    a.m. FC 3 CC .5. At 5 pm I added 2.5 gallons of 182 oz. 6% bleach checked it at 7:30 and it was 10.5.

    On the morning of 7/10 my FC was 5 and the CC was .5. So I lost 5.5 parts of FC overnight but CC hadn't changed. AT 5 pm my FC was down to 2.5 and my CC had increased to 1. So I added 3 gals of the 182 oz. and a recheck at 6:30 showed FC = to 16 and CC was 1.

    This a.m. at 7 my FC was 6.5 and the CC was .5 and probably less since I cold barely see any pink. So I lost 9.5 ppm of FC overnight with still not much CC reading. The posts I've seen with losing lots of FC also have high levels of CC. Since I don't I wonder what is happening to it. In fact most of my CC tests have been barely noticeable before adding the one or 2 drops.

    So from reading as much as I can I assume you will probably tell me that I need to lower my CYA, shock the pool and keep at it until I get a good drop test. Even if that is true, I have a few problems and questions.

    The first relates to measurements. How critical is the "heaping tsp" of DPD powder for the drop test? If some gets on the handle is that "too heaping"? The CLA test is certainly subjective and how do you know when you get it right? The pool store says 100 (twice) but I can get 100 or maybe 80 and my wife can get 120 or maybe 100? I'm 68, maybe that's my problem I tried a 50/50 ratio of pool water to well water last night and it still is hard to tell whether it is 60, 50 or 40.

    Getting my CYA down is problematic since my drained water ends up going down my neighbors front yard. Another problem is that I have a well that puts out 4-5 GPM so it takes a long time to refill. I drained out about 4 inches yesterday and it took about 5 hours to refill. It will take a long time to correct my CYA. By the way the pool store checked my water for iron and copper and there was none.

    So what I would like to do is do as little as possible for the next 5 weeks until I close the pool and deal with the CYA over the winter when I lose some water anyway. Normally the pool gets little use with just my wife and I and often only a few minutes a day when I jump in after a run. Except for a party next weekend that will be the case until the pool closes. So I was thinking of just trying to maintain FC of 3-5 during the day and perhaps adding some algecide (Polyquat 60) to hopefully ward off any signs of algae. Even with all the problems I've had the last 2 years I have had no one get swimmers ear or any other problems and only one algae growth last year.

    Any thoughts greatly appreciated.

    Thanks.
    25,000 gallon inground vinyl sand filter 60 gpm 1 hp pump

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    cubbybeave08's Avatar
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    Re: Where is my FC going ?

    Bob,
    First of all if your CYA is as high as you say it is, you are going to have to bring your Shock level up to about 39 ppm of chlorine. I figured this using the Chlorine/CYA chart...

    pool-school/chlorine_cya_chart_shock

    This means that in order to kill all the organics that you have in your pool at this time, you need to take your FC up to 39 ppm. This is the shock level for someone with CYA of 100...your actual shock number may be higher. Once that holds over night with less than a 1 ppm FC drop you are done shocking and can let it drop to your target FC which would be 12 ppm FC. That is what you need to shoot for. Your minimum is 7 ppm FC. If you are only taking your pool up to 6.5 ppm FC you are not putting enough in to kill all the organics that are causing your algae.

    In order for you to figure out how much of the specific concentrate of Chlorine to add you need to use the Pool Calculator...http://www.poolcalculator.com/. Follow the directions and at the bottom there is a calculator that tells you the effects of adding X amount of Y % bleach to your pool...You have to fill out the specifics for your pool depth and dimensions and etc. This will tell you that if you add 600 ounces of 12 % chlorine or sodium hypochlorite, it will raise your FC X amount of ppm. This will give you a target amount to add to get your pool to 39 ppm or shock level. Once you do that you will need to hold that over night so that you don't loose more than 1 ppm FC and that you have less than .5 CC. Then your pool is sanitized, and you can let it go down to normal target levels after that. Good luck...
    Beave
    Aqua Leader 24ft Round AG Wil-Bar Influence w/54 inch walls 13,500 gallons
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    JasonLion's Avatar
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    Re: Where is my FC going ?

    Your CYA level is really high. It would be best to replace some water to bring the CYA level down to something more reasonable before doing anything else.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Bob_Funk's Avatar
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    Re: Where is my FC going ?

    You should think about having water trucked in
    I consider myself very lucky I found this site before the pool store found me-pool owner since Nov 2008- Stunningly clear 17,000 gal fiberglass pool, thanks to this site, installed in 1982-24" 3.1sq. ft sta-rite sand filter, 1 hp - 2 speed wisperflo pump-WFDS-4

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    Re: Where is my FC going ?

    Quote Originally Posted by bobjdan
    I have a few problems and questions.

    The first relates to measurements. How critical is the "heaping tsp" of DPD powder for the drop test? If some gets on the handle is that "too heaping"?
    The precise amount of powder is not critical, as long as it's not too little. Make sure you're grasping the flat end and scooping with the teensy spoon-like end (some people have been known to scoop up powder on the flat end, that will burn through your powder like there's no tomorrow).

    Quote Originally Posted by bobjdan
    The CLA test is certainly subjective and how do you know when you get it right? The pool store says 100 (twice) but I can get 100 or maybe 80 and my wife can get 120 or maybe 100? I'm 68, maybe that's my problem I tried a 50/50 ratio of pool water to well water last night and it still is hard to tell whether it is 60, 50 or 40.
    Yep, very subjective. And I'm starting to find my arms are getting too short, myself... Anyway, mostly you should do two things. First, be consistent about the lighting conditions when you do the CYA test. Second, when you think you have a reading, pour the stuff in the view tube back into the mixing bottle, and do the view-tube part again. If I get the same answer 2 out of 3 times, I figure I'm good.

    Quote Originally Posted by bobjdan
    So what I would like to do is do as little as possible for the next 5 weeks until I close the pool and deal with the CYA over the winter when I lose some water anyway. Normally the pool gets little use with just my wife and I and often only a few minutes a day when I jump in after a run. Except for a party next weekend that will be the case until the pool closes. So I was thinking of just trying to maintain FC of 3-5 during the day and perhaps adding some algecide (Polyquat 60) to hopefully ward off any signs of algae. Even with all the problems I've had the last 2 years I have had no one get swimmers ear or any other problems and only one algae growth last year.
    Normally I'd suggest the same thing you just said. Except, the trouble is you already have a bit of an algae problem and as a rule the algaecide is more of a preventative than a curative. If you're not going to replace water this fall, you'll need to bring your FC way up like cubbybeave08 said, to take care of that.
    --paulr
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
    AG spa 325 gal, probably Sundance of some kind
    Water testing instructions on one page

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    Re: Where is my FC going ?

    Thanks for all the responses. I am confused about the comment
    , you are going to have to bring your Shock level up to about 39 ppm of chlorine.
    and the different answer I get from the pool calculator. The pool calculator says that with a CYA of 100 my shock level is 26 which is why I added 7 bottles of 182 oz bleach initially. It's strange that I did get a good drop test that first night but not since then.

    I understand the purpose of the overnight drop test, but don't understand why I don't have more combined chlorine. For example, this a.m. I had to look very hard to see the faintest tinge of pink after adding the 5 dpd drops yet lost 4 ppm of FC overnight last night yet only lost 2.5 ppm during the day in about the same amount of time and it was 100 degrees and about 6-7 hours of full sun. So although the "shock" section says to keep the pool at shock level until cc is less than .5 which mine is, I still am losing lots of FC overnight. So is there something happening in the pool that eats chlorine but doesn't register as combined chlorine?

    I also don't understand why if I have some algae I see no evidence of it at all and didn't even when my pool was initially cloudy. I've had green, mustard and black algae at one time or the other over the years and it has always been visible and when I'd shock the pool I could always see piles of light brown/gray dirt looking stuff on the bottom of the pool (except with black algae). When I brush the pool now I see little or nothing cloud up from the bottom other than the bit of debris that gets blown in from the trees, gardens, etc..

    Regarding water getting trucked in, that's pretty expensive and my pool isn't easily accessible. I will talk to my neighbor about flooding his lawn daily over a period of the next week or so to lower my CYA. I can probably do 6-8 inches/day without a problem as long as he doesn't have to cut his grass (actually mostly weeds) in the low spot. After reading many of the posts on this board discussing the trade-offs of CYA levels I may try a CYA level of 70 and see how that works.

    One more question. Has anyone ever seen or know of a problem with higher chlorine levels (e.g. > 5) affecting grass or any other plants/shrubs/trees/ ?

    Note: I'm not questioning the advice given here , but trying to understand what is going on, especially for future problems--which should be easily avoided now that I've found this site.

    Thanks.
    25,000 gallon inground vinyl sand filter 60 gpm 1 hp pump

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    frustratedpoolmom's Avatar
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    Re: Where is my FC going ?

    When my CYA was very high, and I was using high FC levels, I did a series of partial drains and it did not affect the grass or the nearby tree. I also mangaged to get thru that summer with a CYA of 70.

    Yes, you can lose FC and not have high CCs. You have organics that are consuming the FC as it is added, and it is still unseen or "nascent".

    As for shock level, both levels will work, the CYA chart level will work faster, you'll likely use more bleach, perhaps a trade off for speeding up the process.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
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    cubbybeave08's Avatar
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    Re: Where is my FC going ?

    Bobjdan,
    I got that number from the CYA/Chlorine CHart...that tells you what your target FC is for both regular sanitization (everyday) and your shock level...at 100 CYA your shock level is 39...Yes that is very high...but you have huge amounts of CYA and you also have not used enough chlorine to get rid of your contaminants completely, this is why your FC keeps going down so quickly, you need to put enough chlorine in to kill all organic contaminants and still leave chlorine in the pool to kill new contaminants. If you don't kill what is in there now you, you will really only be fighting a loosing battle. And yes I normally would tell someone to drain their pool in partial drainings and then refill, but you did say that you were trying to steer clear of that until closing time...so if you have the ability to use more chlorine...What I suggested will work the fastest and get you swimming more quickly...
    Beave
    Aqua Leader 24ft Round AG Wil-Bar Influence w/54 inch walls 13,500 gallons
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    Re: Where is my FC going ?

    If you're on a municipal sewer system you could drain into the sewer (I run a hose into a near-enough cleanout) and not flood your neighbor. Where I am in fact local code requires draining into the sewer, not the storm drain or ground.

    The pool calculator and Pool School chart differ on some shock levels, I believe they are authored by different people with differing opinions on what's needed at high CYA levels. One of several cases where opinions differ. You are unlikely to go wrong following either of them.
    --paulr
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
    AG spa 325 gal, probably Sundance of some kind
    Water testing instructions on one page

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    Re: Where is my FC going ?

    Quote Originally Posted by bobjdan
    Thanks for all the responses. I am confused about the comment
    , you are going to have to bring your Shock level up to about 39 ppm of chlorine.
    and the different answer I get from the pool calculator. The pool calculator says that with a CYA of 100 my shock level is 26 which is why I added 7 bottles of 182 oz bleach initially. Answered by Paul. There is nothing magic about one particular number but general guidelines to give you some direction.

    It's strange that I did get a good drop test that first night but not since then. Read how to Shock your pool up in Pool School. It is a process, not a one-time doseage.

    I understand the purpose of the overnight drop test, but don't understand why I don't have more combined chlorine. CC's indicate the need to shock. Lack of CC's does not indicate you don't have algae

    For example, this a.m. I had to look very hard to see the faintest tinge of pink after adding the 5 dpd drops yet lost 4 ppm of FC overnight last night yet only lost 2.5 ppm during the day in about the same amount of time and it was 100 degrees and about 6-7 hours of full sun. So although the "shock" section says to keep the pool at shock level until cc is less than .5 which mine is, I still am losing lots of FC overnight.

    You are finished with the shock process when.....
    1. Your pool water is sparkling
    2. Your CC's are .5ppm or less
    3. You can hold your FC overnight without losing more than 1ppm.

    you meet two out of three but aren't quite done yet


    So is there something happening in the pool that eats chlorine but doesn't register as combined chlorine? Yes. See reply two sentences above

    I also don't understand why if I have some algae I see no evidence of it at all and didn't even when my pool was initially cloudy. I've had green, mustard and black algae at one time or the other over the years and it has always been visible and when I'd shock the pool I could always see piles of light brown/gray dirt looking stuff on the bottom of the pool (except with black algae). When I brush the pool now I see little or nothing cloud up from the bottom other than the bit of debris that gets blown in from the trees, gardens, etc..Algae and other organics in your pool can be completely invisible.....they're still there if you are losing FC overnight

    Regarding water getting trucked in, that's pretty expensive and my pool isn't easily accessible. I will talk to my neighbor about flooding his lawn daily over a period of the next week or so to lower my CYA. I can probably do 6-8 inches/day without a problem as long as he doesn't have to cut his grass (actually mostly weeds) in the low spot. After reading many of the posts on this board discussing the trade-offs of CYA levels I may try a CYA level of 70 and see how that works. If you make the effort to reduce CYA (I know it's a PITA), go ahead and bring it down to 50-60.....you and your pool will be much happier

    One more question. Has anyone ever seen or know of a problem with higher chlorine levels (e.g. > 5) affecting grass or any other plants/shrubs/trees/ ?No. Perfectly safe to put pool water onto the lawn....folks do it here on the forum constantly

    Note: I'm not questioning the advice given here , but trying to understand what is going on, especially for future problems--which should be easily avoided now that I've found this site. I don't think anyone is taking it that way, either. Your questions make sense to me and are common issues that come up when someone first discovers the sight. Pool School provides a wealth of information on pool water chemistry

    Thanks.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    cubbybeave08's Avatar
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    Re: Where is my FC going ?

    Note: I'm not questioning the advice given here , but trying to understand what is going on, especially for future problems--which should be easily avoided now that I've found this site.
    Just want you to know Bob, that Dave is right absolutely no offense taken here...My advice usually stems from what I know works for me...I try to keep it simple which is why I use the CYA/Chlorine chart...it is fairly simple to figure out. I don't like to think much once I get home from the office...too much going on there. I hope things work out with your FC...keep learning
    Beave
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    Re: Where is my FC going ?

    Thanks for all the advice. I think I understand how to shock now. I've also drained and replaced about 16 inches of water and am still reading somewhere between 90 and 100 CYA so I may have had more than 100. I went and bought a 100 ft. backwash hose and found the clean out trap in my neighbors yard. It does make draining faster but unfortunately doesn't help the filling rate. It took about 12 hours to replace about 10 inches of water. It's not the time that concerns me as much as the possibility of sucking dirt--or having my pump die on me. It's about due . I never have run out of water running one hose, but if I run 2 at a time in about an hour I start getting muddy water. Unfortunately my neighbor has a lot of iron in his well so I can't use his (which has a lot more GPM). I did that when I initially redid my pool in vinyl and it took me weeks to get all that iron and stain out of my pool. I'll keep working on it and will eventually get the CYA down to a more reasonable level.

    Before going back into shock mode I was going to check my pool light housing for a source of algae and leave it out while I was shocking just in case. However, I can't seem to get the screw out of the top. I tried a Phillips head from outside the pool and when that didn't work I tried looking at the screw head with a mask on but I couldn't really tell if it was Phillips head or one of those Torx? headed screws. The light was put in about 7 years ago. Is anything other than a Phillips head normally used for that screw? With my luck they used a power drill with more torque than my meager hand can produce

    Thanks.
    25,000 gallon inground vinyl sand filter 60 gpm 1 hp pump

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