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Thread: No FC

  1. Back To Top    #1

    Join Date
    Dec 2009
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    San Antonio, Texas
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    No FC

    I bought a house here with my first pool and tested it as soon as we moved in with the previous owners' OTO kit. Chlorine was between 1.5 and 3.0, a TA at around 30ppm, with a pH of 6.8.

    I concentrated on the TA and got that up to 80 ppm, and the pH also rose from 6.8 to 7.2.

    At that point I learned to buy a DPD test kit (from Leslie's - not a DPD-FAS) and learned my
    FC was <0.5, with CC >5.

    I've shocked the pool twice over the last two days, with two pounds of dichlor bags the first time and three pounds the second. Leslie's Total Dissolved Solids showed 1100 and CYA reading is 30ppm. Leslie's FC and pH readings are similar to mine, except that they showed TA 60 when mine showed 70. I don't have a CYA test ability yet.

    This morning's readings: FC = <0.5, TC = 5, CC = 4.5; TA = 60, pH = 6.8.

    (1) So, at this point, should I get the TA and pH back up before shocking again?

    If so, and after that, (2) how long to wait before shocking again, (3) then how frequently should I shock? Weekly? Daily? Hourly? in order to oxidize the CC? (4) Am I using enough dichlor to shock given my circumstances?

    Thanks,
    Jaywalker

    In-ground, 11,000 gallon, plaster, in-line trichlor pucks or BBB bottled chlorine, 1.5 HP pump @ ~100 gallons/minute, cartridge filter

  2. Back To Top    #2
    polyvue's Avatar
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    Re: No FC

    I think you really want to be adding liquid chlorine (or bleach) for shocking. When you shock with Dichlor you're also adding CYA to the water and that may eventually cause problems with keeping up the chlorine. To understand how much chlorine to add, refer to the chlorine cya chart. So, you'll want to have sufficient liquid chlorine to raise the FC to abou 12 ppm and keep it there for an extended period. Here's a great link that explains the process.
    14,555 gal in-ground 16'x29' white plaster Pool w/spa (2007); Goldline Aqua Logic AQL-PS-8 control w/Aqua Cell 15 Salt Water Chlorination (SWCG); Hayward TriStar 1HP (1.85 SF) main / 1.5HP (1.60 SF) spa pumps; Hayward Swimclear cart filter C4025, ColorLogic LED lights; Tankless SP-18-4 electric heater; Polaris 280 cleaner.
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  3. Back To Top    #3

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    Re: No FC

    Jaywalker,

    Welcome to the forum. Most of the answers you seek can be found in pool school. It's a great source to understanding pool water chemistry.

    1. I would raise pH up to 7.4 - 7.6 with 20 mule team borax

    2. If you like, you can raise TA up with baking soda but I would ignore it for now.

    3. Once that's done you should shock the pool but not with dichlor any longer. Dichlor adds too much CYA to your pool and it will quickly get higher than you want. I would use Clorox or 10% liquid chlorine, whichever is easiest to obtain.

    4. Here will be the key to completely sanitizing and clearing your pool.....Shocking is a process not a one time event. Shocking your pool correctly involves bringing your FC to shock level and then holding it there until...

    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.

    I'm sure this post will generate some more questions so ask away....you'll get lot's of great help here from folks who truly understand pool water chemistry.

    There is a good article in pool school that will describe the details of shocking your pool.

    EDIT: polyvue and I are on the same page
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  4. Back To Top    #4

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    Re: No FC

    Thanks. I've read that "Shocking is a process not a one time event," but understood it to mean over the time of your ownership of the pool. Your following statement, "Shocking your pool correctly involves bringing your FC to shock level and then holding it there until..." cleared it up for me; I have to do it continuously over the day. Thanks - that certainly wasn't clear until now, and it certainly answers my timing questions re shock.

    Off to the store.

    Edited: And yes, I did miss that Pool School article. I think I must have concentrated on the chemistry and test kit sections.
    Jaywalker

    In-ground, 11,000 gallon, plaster, in-line trichlor pucks or BBB bottled chlorine, 1.5 HP pump @ ~100 gallons/minute, cartridge filter

  5. Back To Top    #5

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    Re: No FC

    but understood it to mean over the time of your ownership of the pool.
    I've never thought about that....it can certainly be interpreted that way....we're gonna' have to come up with a better way to say it.

    I have to do it continuously over the day.
    Actually, don't be surprised if it takes more than a day....depending on many factors. holding the FC up high (get the CYA/FC relationship chart from pool school) will make it go quickly but a couple of days is quite common.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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