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Thread: Chlorine Discrepancy

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    Chlorine Discrepancy

    Hi All,

    We have a 2 year old 15k gallon gunnite pool. Personal circumstances required that we use a pool maintenance company for the past 5 months. We were able to cancel our service last week and return to the TFP way. I'm stumped about our chlorine level. The pool company was sanitizing with pucks (yeah, i know) and reported weekly chlorine levels between 4 to 6. I just tested the water myself using our Taylor FAS-DPD 870/871 reagents. I was "shocked" to see FAC consistently at 19. I tried testing with an OTO kit and saw an ugly shade of orange. That seemed to validate the FAS-DPD results. I turned down the auto-chlorinator to 1 and retested after one week. I saw the same results. I brought a sample to Leslie's and they measured an FAC/TAC of 6. I figured my reagents went bad. That's unfortunate since I last bought 1 pt bottle of 871 and a 1/4 lb of 870. So, I order a fresh TF-100 kit. I retested this AM and I measure FAC at 21! Can anyone offer any insight?

    FYI, I noticed this post by jblizzle:
    Can these chlorine measurements really be right? - Page 2

    I searched online but cannot find out if Leslies' uses a DPD or FAS-DPD measurement.

    Here is the complete list of Leslie's results (1/17):
    FAC - 6
    TAC - 6
    CH - 250
    CYA - 120 (argh. had this down to 35 before pool company and pucks)
    TA - 70
    pH - 7.4
    Cu - 0
    Fe - 0
    TDS - 0
    Pho - 1000

    Here are the last readings from the pool company (12/28):
    Chlorine - 4
    pH - 7.4
    TA < 80 (they added Alkalinity Plus)

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    Mod Squad tim5055's Avatar
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    Re: Chlorine Discrepancy

    How old is your test kit and where did you keep it stored would be my first question. But if the OTO test showed up orange it does confirm the higher FC level.

    Quote Originally Posted by Richard320 View Post
    On the OTO (yellow) chlorine test:

    Blinding tweety-bird yellow is about 10. School bus yellow is about 12-13. Hunter orange is around 18, up around 25 it starts to look pumpkin orange.
    If Leslies is anywhere near close you want to keep that chlorine at a minimum of 9 at least.

    You don't need to order a complete TF-100, you can get just a "Refill Set for TF-100"
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Chlorine Discrepancy

    Thanks for the response. My latest test used reagents from a brand new TF-100 kit (received Fri).
    I also failed to mention that I tested our tap water using the older reagents and saw 0 FAC.

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    Mod Squad kimkats's Avatar
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    Re: Chlorine Discrepancy

    I would turn off the auto-ch., remove any pucks or such you might have in the tube even if it is turned to 0 as some will "leak out".

    Next I would make sure the pool guy from the service did NOT add something this week. Some times the guys in the field do not get the memo to stop servicing the pool at XX address.

    With the cold temps your pool is not using near as much FC as when it is warmer. SO with you having just stopped the service, the auto-chlo. still turned on, etc your FC is going to be high. It will take time to come down.

    Kim
    TFP Moderator 33x52 round AG 25,600 gals Sand Filter 1.5hp Pump - 2 Speed, SLAM, Pool School, Recommended Levels, Recommended Chemicals, Pool Math, Chlorine/CYA Chart, TF-100 Test Kit

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    Re: Chlorine Discrepancy

    Thanks kimkats, tim5055.

    The pool technicians send an email report right from the job site. I haven't service notices since 12/28 so I don't think there has been addition treatments outside the auto chlorinator.
    It seems like you both feel my measurements are correct and both the pool company and leslie's are way off? If so, any insight to why they would be way off? I just feel like I'm doing something wrong.

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    Mod Squad tim5055's Avatar
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    Re: Chlorine Discrepancy

    If you have read around here much you have probably seen that not much credence is given to pool store testing. While you would think that a "professional" would be the best, unfortunately in most cases it is quite the opposite. Between employees who blindly trust the word of chemical sales representatives and high school kids working in the pool store for the summer you end up with poor results from their testing. In my case two different pool stores told me my CYA was "fine", around 70 or 80. When I tested myself I found it over 200.

    I bet the pool service just used an OTO test which had a limit of 5 When it was a little darker they just called it 6. Leslies may have used an OTO also.

    Trust your own testing, you care about your pool more than they do.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Mod Squad kimkats's Avatar
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    Re: Chlorine Discrepancy

    What Tim said...........I took my wonderfully balanced water to THREE different pool stores within an hour or less of taking it out of the pool just to "test" them. They ALL failed! Each one said this or that was wrong! It would have cost any where from $50 to $125 to "fix"!

    They are there to sell you stuff so......

    Trust YOUR tests. We can/will walk you through the test if you want to make double sure you are doing it right. Here is a video to help just in case that will help!

    How to Use a Taylor Complete FAS-DPD Pool Water Test Kit K-2006 - YouTube

    Kim
    TFP Moderator 33x52 round AG 25,600 gals Sand Filter 1.5hp Pump - 2 Speed, SLAM, Pool School, Recommended Levels, Recommended Chemicals, Pool Math, Chlorine/CYA Chart, TF-100 Test Kit

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    Chlorine Discrepancy

    There's little use in debating what went wrong with the pool store. As Kim and Tim (and thousands of others can attest to), they just stink at testing and, honestly, they don't care if they are right or wrong. Either way, they sell you something, even if it's just an overpriced jar of baking soda (Alk-Up is what they call it).

    Your task now will be to rectify the damage done by the pool service. Your CYA is way too high and, while cold out now, it won't hurt you but, come spring time and warmer water temps, it will be hard to keep the water algae free. You need to drain 50% of your pool, refill with fresh water and then balance out your water chemistry. If you do it now, you'll be ahead of the game come spring time. If you wait, you'll fall behind the 8-ball and will be trying to fend off an algae bloom while trying to balance you chemistry.


    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: Chlorine Discrepancy

    I'll trust my measurements and move on.

    Our city uses the Nov/Dec/Jan water usage to set our waste water charges for the rest of the year. I'd either have to pay for an extra 7500 gallons waste water * 9 months or bring in a water truck if I drain the pool now. I think I'll wait until Feb before working on my CYA.

    Thanks all. You're an incredibly responsive group!

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    Re: Chlorine Discrepancy

    You can still manage your pool with a 120 CYA. I started off at 200 and have slowly but surely got my CYA down to 80 just using rain water. The trick is letting the FC come down under 10 occasionally to check your PH. I have to admit I cheated a little and was tracking ph at a fc of 12 but the ph still seemed accurate.

    Mark, Pool: 30,000 gallon, IG Vinyl, Pentair Superflo Variable Speed 1.5 HP pump, Hayward S220T Sand Filter, Taylor k-2006 Test kit with speedstir. Dolphin Nautilus Plus.
    Hot Tub: Hot Spring Grandee 450 Gallons, Ace System (Salt water Chlorine Generator) Dichlor / Bleach method. Taylor K1766 Salt Test.

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    Mod Squad kimkats's Avatar
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    Re: Chlorine Discrepancy

    I hear you on waiting! Good call............just make sure you do it before the temps start getting over 60. That should give you some time.

    Kim
    TFP Moderator 33x52 round AG 25,600 gals Sand Filter 1.5hp Pump - 2 Speed, SLAM, Pool School, Recommended Levels, Recommended Chemicals, Pool Math, Chlorine/CYA Chart, TF-100 Test Kit

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    Re: Chlorine Discrepancy

    Quote Originally Posted by Alwayswantedapool View Post
    You can still manage your pool with a 120 CYA. I started off at 200 and have slowly but surely got my CYA down to 80 just using rain water. The trick is letting the FC come down under 10 occasionally to check your PH. I have to admit I cheated a little and was tracking ph at a fc of 12 but the ph still seemed accurate.

    Sent from my GT-P5113 using Tapatalk
    While possible, this is not a good suggestion. One slip that lets Algae bloom and you're in deep trouble. Just as importantly, this will require a lot of extra chlorine.
    TFP Moderator
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    JoyfulNoise's Avatar
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    Re: Chlorine Discrepancy

    Quote Originally Posted by Patrick_B View Post
    While possible, this is not a good suggestion. One slip that lets Algae bloom and you're in deep trouble. Just as importantly, this will require a lot of extra chlorine.
    I did the calculations based on the OPs pool size and, assuming normal FC losses during the hot weather, it would roughly take about 1 gallon of 8.25% bleach every 2 days to keep the FC between 9-14.8ppm FC. If a SLAM was needed, then you're looking at over 5 gallons of bleach to get to 48ppm FC. If you factor in the cost of bleach plus the cost of test reagent refills you would need to buy after constantly titrating 9-15ppm FC in the FAS-DPD test, then you could easily spend as much money as it would cost to simply drain half the pool water (7500 Gal or roughly 10CCF water). Unless the OP has astronomical water rates or water restrictions, a drain and refill is more cost effective.


    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Mod Squad tim5055's Avatar
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    Re: Chlorine Discrepancy

    Quote Originally Posted by JoyfulNoise View Post
    Unless the OP has astronomical water rates or water restrictions, a drain and refill is more cost effective.
    Matt,

    What he has are sewer rates that are based on the water he uses now. When I lived in Fairfax County, VA they did it this way.

    They take note of the water use during the three "winter" months and average it, assuming anything over this usage in the summer is outdoors and not going into the sewer. If he drains/refills during those 3 months he will be paying higher sewer rates for the next year because of it.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Chlorine Discrepancy

    Maybe they offer a special credit for these situations I don't know, but lots of cities will issue evaporation credits for certain situations. Maybe they can do something similar.
    TFP Moderator
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    Mod Squad tim5055's Avatar
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    Re: Chlorine Discrepancy

    Quote Originally Posted by Patrick_B View Post
    Maybe they offer a special credit for these situations I don't know, but lots of cities will issue evaporation credits for certain situations. Maybe they can do something similar.
    It's wierd, but the only credit Fairfax would give is a leak from a pipe burst that you have a receipt for the repairs.

    Feb is not that far away for a drain then.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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