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Thread: Need advice: New member - first pool - first test results

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    Join Date
    May 2008
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    Need advice: New member - first pool - first test results

    I am renting a house close to Sacramento CA that comes with an outdoor pool – this will be my first attempt at maintaining one. It is a 10,000 gallon, in-ground, masonry pool, with cartridge filter, small water fall (currently hardly-ever used), and no other additional equipment. I cleaned the four cartridge filters last weekend (tons of stuff came off) and the filter pump is currently set to run 4 hours per day. The pool water generally looks clear, but has a lot of tiny particulate matter floating around. The surface area of the pool walls/floor look dark grey with white spots – the walls/floor receiving less sunlight are darker (could be stains or the top-coat of plaster rubbed off). The same walls (that receive less sunlight) are starting to grow algae light “green” in color. I scrub the walls once a week with a Stainless Steel brush. Sanitation is accomplished through one of those floating gadgets, dispensing 3” Trichloro tablets.

    Have been lurking on the site to get better educated and decided to switch over to the BBB method. Just received the T-100 test kit and my initial readings (accomplished once last night and once this morning) are as follows:
    FC = 5
    CC = 0
    TC = 5
    TA = 170
    CH = 250
    CYA = 90
    CSI = 0.79
    Temp = 77 degrees

    I plugged the numbers into the Pool Calculator and it tells me to do the following:

    1) Lower the pH to 7.2
    2) Add 145 oz of 6% bleach (to get to FC of 13) or (373 oz to get to FC of 23 to shock the pool)
    3) Add 46 oz of 31.45% Muratic Acid
    4) Add 74 oz of Calcium Chloride

    My first thoughts are to lower the pH with Muratic Acid (not sure how far to lower), raise the chlorine level with bleach ASAP (maybe even shock the pool - FC of 23), then add the calcium chloride. I need to scrub the walls more often, and think I ought to increase the run time of the pump to 8 hours per day and leave the water fall on whenever the pump runs to help aerate the water.

    I'm sure there is a lot more I ought to be doing - am looking for your sage advice on what I need to do and proper sequence of tasks.

    Thank you VERY MUCH (in advance) for your help – you all have a terrific site here!!!!

    Heinz
    gunnite bottom and fiberglass walls that have been coated with epoxy paint. Approx. 24000 gallons, sand filter.

  2. Back To Top    #2
    JasonLion's Avatar
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    Welcome to TFP!

    You didn't actually say what your PH level is. You should probably bring the PH down to between 7.0 and 7.4, both to help the chlorine be more effective and because your CSI is on the high side and some of your description sounds like calcium scaling. Calcium scaling happens when the PH is high and either CH or TA or both are high. Reducing TA also calls for bring PH down, see below.

    If you have algae actively growing then you need to shock the pool. Shocking means bringing your FC level up to about 23 (because of your high CYA level) and holding it there by testing and adding chlorine as needed to maintain the FC level. You should also brush the entire pool each day while the chlorine level is high.

    Your TA is rather high. This will both cause the PH to rise slowly and promotes calcium scaling. To bring TA down you can follow the procedure in this thread.

    Do not add calcium at this time. You should bring the TA down first and won't need any CH until your TA is much lower.

    Long term you should work on bringing your CYA level down. With CYA at 90 you need to maintain a FC level between 7 and 12. As the CYA level comes down you will be able to lower that a little.
    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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    How long to hold high FC for shock?

    Oops, forgot about the pH level - it is out there at 8.2. I added the Muratic Acid this morning - tested one hour later and pH was 7.4... will test periodically as I drive it down to 7.0-7.4. Added bleach and FC is up to 15.5 (CC still 0) - will continue to add until FC reaches 23. How long should it be held there to shock?

    Have read through the procedure to lower TA and will start that this weekend.

    Not sure how to bring the CYA level down yet - will search the threads this evening.

    Thank you VERY much for your help - I feel like I'm already making progress!

    Heinz
    gunnite bottom and fiberglass walls that have been coated with epoxy paint. Approx. 24000 gallons, sand filter.

  4. Back To Top    #4
    Keep it at 23 until you can hold that level overnight, and your cc's are 1 or less.

    Welcome to TFP!

    8000 gallon 20' x 48" round vinyl frame pool, 12" sand filter (don't have the specs on the pump), TF100 test kit
    Handy Links: PoolMath, TF-100 Test Kit, Pool School, CYA-Chlorine Chart
    "Shock" is a process, not a product!

  5. Back To Top    #5
    JasonLion's Avatar
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    You want to keep the pool at shock level till you don't lose any FC overnight, CC is 0.5 or lower, and the water is clear.

    The only practical way to lower CYA is to replace water. Some water replacement will happen naturally because of splash out, backwashing, and overflow. Given that you are only a little over the max recommendation you might as well let it fall naturally. Just avoid using anything that will add more CYA to the pool.
    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

  6. Back To Top    #6

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    I will be holding the FC at 23 (with a CYA of 90)... until it stays there overnight - having said that...

    Will be unsafe for people to use the pool during that time - or just a chemical irritant due to the high FC?
    If it is unsafe, when will I be able to safely let people back into the water ?
    gunnite bottom and fiberglass walls that have been coated with epoxy paint. Approx. 24000 gallons, sand filter.

  7. Back To Top    #7
    JasonLion's Avatar
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    Opinions vary a little. I believe that it is totally safe to swim but that it is best to have a shower right after. The active chlorine level is lower than in most indoor public pools but the total chlorine level is very high. Because the active level is low it is safe, but it is best to rinse that total chlorine level off before it can react as you dry off. I have heard others say swim with no worries and a few who say wait till the FC level is down to the high end of the normal FC range for your CYA level before swimming.
    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

  8. Back To Top    #8

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    Thank you all for your help - you're awesome! Heinz
    gunnite bottom and fiberglass walls that have been coated with epoxy paint. Approx. 24000 gallons, sand filter.

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    New question

    I understand that when raising the FC to shock, that I need to bring the FC up to 23 until it maintains 23 overnight. I did that last night - BUT, for some reason, the FC went up to 26 last night and dropped to 23 this morning. Question is:

    Is an FC of 23 some magic limit (it won't hold overnight above that), or should the pool have held 26 overnight (provided eveything else is alright)?

    Thanks for your help, Heinz
    gunnite bottom and fiberglass walls that have been coated with epoxy paint. Approx. 24000 gallons, sand filter.

  10. Back To Top    #10
    JasonLion's Avatar
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    No, 23 isn't a magic number. That is just a level that experience has shown will reliably kill algae with CYA around 90. If it failed to hold at 26 it means that there are some organics in the pool, probably algae, that the chlorine is breaking down. Try it again tonight and see how you do.
    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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