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Thread: Need to drain pool - Questions - don't want to harm pool

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    Need to drain pool - Questions - don't want to harm pool

    Hey everyone, I just bought a house a couple weeks ago and after testing the pool I'm realizing the previous owners pool guy didn't do such a great job with the chemicals.

    Pool is an inground Gunite pool I believe. Around 15k gallons.

    I have alot of experience testing water as I previously owned a very large reef aquarium so I pretty sure my testing with my new TF100 kit is fairly accurate.
    CH is sky high = 540! BTW, my tap is only 160
    CYA is off the scale and if i had to guess it's 110-120

    Pool calculator is saying I need dump around 65% to get my cya to 40

    I've been reading about draining the pool and how hydrostatic pressure can cause the pool various issues. I just want some opinions on this. Like I said I won't be draining the entire pool.

    Not sure if temperature comes into play, but it's been getting down to low 30s at night, so the ground is cool. I would probably pick a day that was in the 50-60's to do this.

    Thanks for any advice you have!
    15,000 gallon SWG (plaster)
    Hayward DE4820 Filter
    Whisperflo WFE-4 1 hp pump
    T-9 Salt Cell
    Aqua Rite Goldline Control

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    mas985's Avatar
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    Re: Need to drain pool - Questions - don't want to harm pool

    First, welcome to the forum.

    A CH of 540 ppm is a little high but not too bad. I have run mine at close to 800 ppm without a problem. However, the CYA is a bit high and could do with a water swap.

    This past year I did an inplace refill for the first time. I pumped water from the main drain to waste, without returning any water to the pool, while adding water to the shallow end. So the pool level never changed but I was able to replace about 1/2 the water without any risk. The key is to keep the water very still and not return any of the water through the return eyeballs which would cause mixing. You could do this with a sump pump or even siphon water out of the deep end but you would need an elevation change to do that. Just another option if your water table is high or concerned about the pool lifting out of the ground.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Need to drain pool - Questions - don't want to harm pool

    Unfortunately the only way to drop Cyanuric acid levels is by draining the pool. And at your levels @ 65% is a good amount. Leaving 35% of your water in the pool will not cause a problem you still have plenty of “water” weight to keep pool in place. If you were to drain your pool completely to scrub/paint/maintenance, you would have to watch the water table because an empty pool will want to float like a boat and come out of the ground from the ground pressure. You would just want to drain it completely when the ground is dry and only keep it empty for a short period of time. After you fill the pool back up be careful not to add too much additional cyanuric acid (stabilizer/ conditioner) because it is already present in many forms of chlorine tablets.

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    Guest

    Re: Need to drain pool - Questions - don't want to harm pool

    Quote Originally Posted by paulsimmons
    Unfortunately the only way to drop Cyanuric acid levels is by draining the pool. And at your levels @ 65% is a good amount. Leaving 35% of your water in the pool will not cause a problem you still have plenty of “water” weight to keep pool in place. If you were to drain your pool completely to scrub/paint/maintenance, you would have to watch the water table because an empty pool will want to float like a boat and come out of the ground from the ground pressure. You would just want to drain it completely when the ground is dry and only keep it empty for a short period of time. After you fill the pool back up be careful not to add too much additional cyanuric acid (stabilizer/ conditioner) because it is already present in many forms of chlorine tablets.
    Partially true, CYA can also be REMOVED by Reverse Osmosis

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    Re: Need to drain pool - Questions - don't want to harm pool

    Reverse osmosis... What would be the timeframe and cost factor for removing 65% of the inquirer's CYA by reverse osmosis? It's generally accepted that the least expensive and most time friendly method for lowering CYA is to drain & refill. Please supply method solutions and cost evaluations for reverse osmosis so we, the unwashed, can compare. If it's not cost effective, why even suggest it?
    APSP CST Certified
    17k inground concrete; 1.5hp 2 speed Tristar pump, 300sq.ft. Cartridge filter, AquaLogic PS-4 w/ Tcell-15, Navigator suction cleaner.

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    Re: Need to drain pool - Questions - don't want to harm pool

    Example...

    15,000 gallons, TDS 4,000 ppm, CYA 100 ppm +, and CH 1,000 ppm

    7 - 8 hours of run time

    $375.00

    When completed

    CYA is 0ppm, TDS is 800ppm and CH is 200ppm

    Water rates in Southern California are around 4 dollars per unit (750 gallons).

    20 units = 15,000 gallons
    20 x $4 = $80.00 x 2 (drain and refill) = $160
    $160.00 + $35 (rent a sump) $195.00
    $195 + $150 (pool service professional fee) = $345.00


    Save up to 85% of existing pool water
    Plaster is never exposed
    Pool is never down
    No chance of pool floating
    Better quality water
    Helps dissolve tile line calcification
    And much more....

    Not to mention, some counties in Southern California are requiring permits and limitations on how often you can D/R.

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    Re: Need to drain pool - Questions - don't want to harm pool

    I don't think that we have any RO service(s) here in DFW. At least, not yet anyway.

    Before swapping lots of water, check to make sure that the city isn't doing sewer averaging right now. Most municipalities do this in the winter when folks aren't watering so much. Would hate for you to drain and fill 10K gallons and have that bump your sewer rates up for the next year. Or, you could just make sure that you have residual FC in there and let things ride until the spring.

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    Re: Need to drain pool - Questions - don't want to harm pool

    257WbyMag,

    Not Yet.... But it's coming

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    Re: Need to drain pool - Questions - don't want to harm pool

    Quote Originally Posted by salp
    257WbyMag,

    Not Yet.... But it's coming
    This is good news of course.

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    Re: Need to drain pool - Questions - don't want to harm pool

    Let me add to Sal's post, Ranger. There would be no reason to remove only 65% of the water with the R/O rig. The exact amount of water would be cleaned to achieve the level of CH required for safety to the plaster, which in turn would remove all of the CYA. Additionally, unless the method of removal would be exactly like mas985 described, you would not be assured of removing the harder water with a 65% drain, as the harder water sits lower in the pool (I know; we'll get some rebuttal to this statement, but we have proved it).

    Water is plentiful in many parts of the Country, but not all. While the norm has always been preached to drain and refill (starting to sound like other erroneous information spewed in the pool industry that we fight so hard on this page?!), it is not prudent in many cities/states. R/O is an inexpensive solution to handling existing pool water in drought stricken areas, places with high CH levels and evaporation (Arizona, for example), and pools that are "over chemicaled".

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    Re: Need to drain pool - Questions - don't want to harm pool

    Quote Originally Posted by salp
    257WbyMag,

    Not Yet.... But it's coming
    Bring it on!
    20K gal IG plaster pool, Manually chlorinated with 6% bleach, 1.5 HP Sta-Rite Dura-Glas II pump, Pentair FNS Plus 48 DE filter, Polaris 280

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    Re: Need to drain pool - Questions - don't want to harm pool

    Quote Originally Posted by 257WbyMag
    Or, you could just make sure that you have residual FC in there and let things ride until the spring.
    This is what I would do. From reading lots and lots of posts on this forum I have learned that high CYA is doable with proper monitoring. I guess it all depends on water costs in your area. Using the BBB method it should drop on its own over time.
    11,872 Gallon IG Shotcrete play pool
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