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Thread: Testing for lower levels of TC, FC

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    Testing for lower levels of TC, FC

    Hi. This question is about what testing options there are that can be used to test for lower levels of TC and FC.

    First, some details:
    1st year with in-ground pool
    20x40, 3 feet shallow, 8 feet deep end, liner, approximately 24k gallons.
    DE filter
    Electric heater
    DeltaUV system

    CYA level is 30 ppm

    Looking to maintain FC levels around 0.5 ppm.

    The question is, what test system is good for measuring at these levels especially for the TC/FC differential?

    Let me know if you need more details.

    Thanks,
    Paul

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    Texas Splash's Avatar
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    Re: Testing for lower levels of TC, FC

    Hello Paul and welcome to TFP. I have to say, that's a bit of an unusual question for us. 0.5 ppm is extremely low. Is this an indoor pool, or is there a specific reason you have a desire to maintain FC so low? Many of us here use the FAD-DPD reagent method to test FC & CC at various levels.

    Also, please add your pool info to your signature by going to the top of the TFP web page (just under the Pool School button) and select "SETTINGS". On the next page look to the left for a menu bar that says, “MY SETTINGS” and go to "EDIT SIGNATURE" to enter your pool and equipment info there. It will help us later. This link may also help you: Pool School - Read This BEFORE You Post.

    Nice to have you with us.
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    Re: Testing for lower levels of TC, FC

    0.5ppm is nowhere near enough for proper sanitation and algae kill.

    You need to be at absolutely no less than 2ppm and 4ppm is considered target.
    Bob - Palm Beach by San Juan Pools. approx 5000 gals., Pentair 320 cartridge filter (all new guts installed by me), Goldline SWG, 'New to me' Kreepy Krauly Sand Shark, Intermec 104 Timer Test kit: TF-100 w/Speed Stir

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    Re: Testing for lower levels of TC, FC

    Hi. Thanks for the response. Sorry, I neglected to mention this is an outdoor pool. The reason for the 0.5 ppm level is the recommendation with use of the UV system.

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    Re: Testing for lower levels of TC, FC

    Outdoor pools get no benefit from UV systems. There are many threads about it all around this site. The claims made by the UV folks have yet to be proven in real world testing.

    - - - Updated - - -

    Here is a good one to read: Alternative sanitizers and pools--The Truth!
    Bob - Palm Beach by San Juan Pools. approx 5000 gals., Pentair 320 cartridge filter (all new guts installed by me), Goldline SWG, 'New to me' Kreepy Krauly Sand Shark, Intermec 104 Timer Test kit: TF-100 w/Speed Stir

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    Re: Testing for lower levels of TC, FC

    Thanks. But my question is in regards to how to test for the levels of chlorine, not what type of system I should get. Time will simply tell and I always have the option of increasing. But for now, my question is how best to test for the levels I've mentioned. Thanks.

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    Re: Testing for lower levels of TC, FC

    You want the FAS-DPD test portion as seen HERE.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
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    Re: Testing for lower levels of TC, FC

    The lowest you can get with Taylor reagents FAS-DPD test is 0.2 ppm FC/CC with a 25 mL sample instead of a 10 mL sample.

    https://www.taylortechnologies.com/I...tions/5216.pdf
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    Re: Testing for lower levels of TC, FC

    Thanks. I did see that one. I believe that is 0.2 ppm with 0.2 ppm steps if I'm not mistaken?

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    Re: Testing for lower levels of TC, FC

    Yes. The FAS-DPD test from Taylor can be purchased individually or as part of a kit such as the K-2006 or the TF-100 from tftestkits.com. Both are made using Taylor reagents. Ordering it from the link Texas Splash posted will assure you get fresh reagents with the test. You can get it online at other sites, but never know if they are fresh reagents or not.
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
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    Re: Testing for lower levels of TC, FC

    Phizy, Welcome to,TFP!

    I guess you can see the folks here are passionate about pool care and the method we have found that works.

    I wish you luck with your UV system and low chlorine, but do want to caution you about one thing. UV, ozone and other "low chlorine" systems are certified by the EPA as secondary sanitation systems due to the long kill time for much of the bad stuff that can find its way into pool water. With these secondary systems they require a minimum of 1ppm FC at all times for faster kill rates. I would just recommend you target 1ppm rather then try to regulate your pool at .5ppm.

    Stick around and keep us posted on your progress.
    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: Testing for lower levels of TC, FC

    I should warn you that the recommendation from the UV manufacturer is not taking in to account your CYA level. With a CYA level of 30 0.5 ppm FC is not high enough to sanitize your water. You really want to target 1 ppm or higher, or lower your CYA to 15 or lower (which isn't feasible since you can't measure that low, but that is the highest CYA at which 0.5 ppm is sufficient) to keep your water safe.
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    Re: Testing for lower levels of TC, FC

    Thanks. I did request some further information and literature references from Delta UV on this. Consequentially, its difficult to maintain that low of a chlorine level right now with the solar cover on. So, right now, the FC is around 2.5 ppm (total is about the same). This is also why I wasn't setting a CYA concentration much above 30.

    If anyone has any authoritative references I would appreciate it.

    Also...as a follow up. Considering the FROG mineral system, the report FC is 0.5 - 1 (max) with CYA between 20-80. These values seem to contradict the recommendations above. Is there a reason these are ok?

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    Re: Testing for lower levels of TC, FC

    Quote Originally Posted by Phizy View Post
    Also...as a follow up. Considering the FROG mineral system, the report FC is 0.5 - 1 (max) with CYA between 20-80. These values seem to contradict the recommendations above. Is there a reason these are ok?
    Not really. We don't advocate/recommend any mineral/low-lower chlorine system.

    I'm sure if tested and watched closely you can run a pool with these type systems, but we feel there are easier ways to maintain your pool that we are sure will be safer (quicker kill times for pathogens), prohibit the growth of algae, less expensive and no possibility of mineral staining.

    TFP is all about easier (Trouble Free) ways of maintaining a residential pool without using expensive "specialty" products. It's just who we are.

    I guess in a way questions like you are asking (you are not the first, nor will you be the last) would be like going to a vegan forum and asking the best way to grill a steak. There is awareness that it happens, but folks there don't do those kind of things.

    We welcome your participation but most folks probably won't be able to help with specific questions you may have.
    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: Testing for lower levels of TC, FC

    That's an interesting response. Basically, if I read this right, TFP is basically about tried and true methods based on years of experience and doesn't really tackle new systems? I suppose that is fair. I would also assume then that when advice is provided such as "those systems don't work" it is not based on evidence but rather a lack of experience on new technology?

    Contrast though, that UV systems are not entirely new systems.

    I would only ask that if such contradictory statements are provided (i.e. "doesn't work") that a reference be given to help understand the basis of such comments?

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    Re: Testing for lower levels of TC, FC

    P
    Quote Originally Posted by Phizy View Post
    That's an interesting response. Basically, if I read this right, TFP is basically about tried and true methods based on years of experience and doesn't really tackle new systems? I suppose that is fair. I would also assume then that when advice is provided such as "those systems don't work" it is not based on evidence but rather a lack of experience on new technology?

    Contrast though, that UV systems are not entirely new systems.

    I would only ask that if such contradictory statements are provided (i.e. "doesn't work") that a reference be given to help understand the basis of such comments?
    The basis of "doesn't work" in many cases is the hundreds of Frog, Baqua and other "alternative" system owners who show up here looking for help with out of control pools.

    No, UV are not new systems but are generally directed at large commercial pools with high bather loads, thus needing supplemental UV to control CC. Our members are outdoor residential pool owners for the most part looking for the easiest way to maintain their pool. UV, ozone, mineral and other alternative pool care methods just don't fit that description.

    We are not the Consumer Reports of pool products. We advocate the use of what we know works the best for the least outlay of folks hard earned money.
    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: Testing for lower levels of TC, FC

    Whenever your pump is not running, only the residual chlorine is killing pathogens. The kill rate of most has been calculated in reference to the active chlorine level, which is directly affected by your cya level.

    So, if you run your pump 24/7, yes your UV system is attacking anything in the UV chamber at that moment. But what's going on back in your pool, or when the pump stops, is entirely up to the fc level. There are many many factors that determine how likely a pool is to see a problem, and yours might be fine in perpetuity. But there's only one way we advocate of ensuring there is no problem, and that is daily testing and dosing with chlorine according to the fc/cya chart.
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    Re: Testing for lower levels of TC, FC

    Well, thanks for the information. I think the topic has moved away from the original intent which was how to test for lower levels of TC/FC. Ultimately, proper pool maintenance is about proper control which was the goal of this post. We'll see what the future brings. I'll post experiences back to this in the future so others who search for this topic have some information as well.
    Thanks again.

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    Re: Testing for lower levels of TC, FC

    I wonder if it would be possible to use 50 milliliters of water and then it dropped would be 0.1? It is going to take a lot of powder for a sample that size though.
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    Re: Testing for lower levels of TC, FC

    I thought about that as well and when I talked with Taylor Tech, they mentioned that. As compared to using strips, this will be far better anyway. The store down the road from me will analyze for free using the Lemotte spin system.

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