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Thread: Need a little advice on sanitizing systems.

  1. Back To Top    #1

    In the Industry

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    Oct 2014
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    Belmont, WI
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    Need a little advice on sanitizing systems.

    I am in the process of figuring out a new chlorine delivery system for a pool I manage and am in need of help. I have an indoor pool and spa (both commercial) and the owner has been running triclor through it for some time so you can guess what the state said when they came in and tested it....."Your closed". I had about 150 ppm of cya and just to keep the pool sanitized I had to keep the FC above 20 ppm.
    Like I said I am looking for a new chlorine delivery system but I also need to see the reality that I will not be at this job for the rest of my life so I need this system to be idot proof.
    We do have a chemtrol 255 that controls the feeders for our mereatic acid and triclor feeders, but I do not think that they are running correctly because the spa will feed triclor untill the orp is 807 with a FC of over 60 ppm and the pool with an orp of 714 will have FC of 14 ppm. I do understand that before I can hook up a new system I have to figure this out.
    I am looking in to calhypo and liquid chlorine. The setup for calhypo will be 600 but the tablets will be more expensive. where the liquid will cost 2100 to set up but I will be able to run 8.25% bleach through it at a cost of $1.50 a gallon (from walmart).
    What are your thoughts, Please?
    Thanks
    Marc
    Pool: 16823 Gal/In Door/IG (Plaster)/Sand Filter/Chlorine/Apx 10y old/ORG and pH meter with auto supply of chem/2 Skimmers/2 Drain
    Whirlpool: 781 Gal/In Door/IG (Plaster)/Sand Filter/Not sure of San/Apx 10y old/ORG and pH meter with auto supply of chem
    Test both with Taylor K-2006 daily.

  2. Back To Top    #2
    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    Re: Need a little advice on sanitizing systems.

    First, you must replace nearly all of the water and get the CYA level down to 30 or lower, possibly much lower depending on your exact goals. Meanwhile, disable the trichlor tablet feed system and do not use it any further, since using any more trichlor is only going to mean yet more water replacement.

    I am assuming the FC levels and ORP readings you quote are with the currently very very high CYA level. Once CYA comes down to something more reasonable, it will be possible to get plausible ORP readings at plausible FC readings. What are the ORP set points you are currently using and how did you arrive at them? The normal approach is to manually adjust things to where you want them to be, take an ORP reading at that point, and then adjust the ORP set point to that reading. This "calibration" should be done regularly, as the FC/ORP relationship can change over time.

    I recommend feeding bleach/liquid chlorine. Cal-hypo will slowly add calcium, which could eventually get too high and cause serious problems of it's own. By the by, bleach/liquid chlorine can be purchased in 50 gallon drums for very attractive prices in most areas. A commercial pool usually uses enough chlorine to make that a plausible approach.

    Do you have any schedule of regular water replacement? It doesn't sound like you have been replacing water on a regular basis, which is normally done for a commercial pool.

    We recommend keeping CYA around 20 for an indoor pool. However that is not allowed for commercial pools in some jurisdictions. Do you know what the rules for FC levels and CYA levels are in your area?
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  3. Back To Top    #3

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    Re: Need a little advice on sanitizing systems.

    Wisconsin state pool codes in this link state the following:

    DHS 172.14 4(b) Cyanurates. The water cyanuric acid concentration may not exceed 30 ppm.
    (f) Maximum chlorine residual. The maximum chlorine residual in any pool shall not exceed 10 ppm.
    Table DHS 172.14 Minimum FC in Whirlpool with Stabilizer is 4 ppm. Minimum FC in Swimming and Activity Pool with Stabilizer is 1.5 ppm.
    So fortunately one can use some CYA and have a higher FC limit. That will help to keep FC in the indoor pool and spa. I'd suggest targeting 4 ppm FC with 20 ppm CYA for the pool and 4-6 ppm FC with 30 ppm CYA for the spa. This will be equivalent to 0.1 to 0.2 ppm FC (dependent on temperature) with no CYA for the pool and 0.2 to 0.4 ppm FC with no CYA (assuming 104F) for the spa. This should be pleasant for users, provide sufficient disinfection, and provide sufficient FC to not get used up too quickly with varying bather load though a responsive dosing system should be able to keep up.

    I agree with Jason that Cal-Hypo is not a good choice because for every 10 ppm FC added by Cal-Hypo it also increases Calcium Hardness (CH) by 7 ppm and scaling is particularly problematic and more likely in spas due to the higher temperatures. The only way you'd be able to use Cal-Hypo effectively is if you were to have regular significant water replacement.

    The ANSI/APSP-11 2009 standard specifies 7 gallons per bather for water replacement in a pool. It would be more accurate to have that be bather-hours in case swimmers are in the pool longer (say, a swim team). For spas, the Water Replacement Interval (WRI) is given by the following formula:

    WRI (days) = (1/3) x (Spa Volume in U.S. Gallons) / (Number of Bathers Per Day)

    In this case, the soak time is assumed not to be one hour but more likely to be 20 minutes if spa temperatures are hot (104F). So the factor of (1/3) would be (1/9) if you were dividing by the number of person-hours per day. Note that Wisconsin does not have any required water replacement in their state pool/spa code.
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    In the Industry

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    Oct 2014
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    Belmont, WI
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    Re: Need a little advice on sanitizing systems.

    Thanks for the reply's guys. After a bit of her yelling and me giving my 2 week notice, the owner has decided to go liquid chlorine. The ironic part of things is after I gave my 2 week the spa is finally coming in line, the pool has been there for weeks. Thanks for all the information and help that has been given to me from every one on TFP. I have learned alot about pool care and the lack of in commercial pools. I will be getting a test kit of my own from here on out before I get into another commercial pool.
    Thanks again
    M
    Pool: 16823 Gal/In Door/IG (Plaster)/Sand Filter/Chlorine/Apx 10y old/ORG and pH meter with auto supply of chem/2 Skimmers/2 Drain
    Whirlpool: 781 Gal/In Door/IG (Plaster)/Sand Filter/Not sure of San/Apx 10y old/ORG and pH meter with auto supply of chem
    Test both with Taylor K-2006 daily.

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