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Thread: fiberglass pool water change question

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    fiberglass pool water change question

    First of many thanks to this forum and how its been extremely helpful. 4 years ago I had a 15k gal fiberglass pool installed. Using the liquid bleach everyday and a little muriatic acid once in a while I never seem to have to add anything else. The only time I've ever shocked is each spring when opening.
    My total alk always seems to stay at ~90 +/- 10
    Ca hardness has gradually increase from about 140 to 190 in 4 years time
    CYA has always between 30-40

    my question is: Do I need to decant some of this pool water (say 50-75%) and make up w some fresh( municipal) water just because of of its age?
    It just seems weird swimming in water that is 4yrs old ( only new water ever added was for evaporation and splash out) even though water current water appears fine.
    15k gal inground Viking fiberglass pool; Hayward Variable 1.5hp pump (Maxflo VS); Hayward swimclear 325 sg ft cartridge filter; Raypak 206A 199k btu nat gas heater; Aquabot Bravo robotic pool cleaner

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    JoyfulNoise's Avatar
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    fiberglass pool water change question

    Nope, no need to discharge any water. Your water is fine.

    There's no such thing as "old water" as that is an "old concept" used by "old" service techs back in the day when there were not any good methods for measuring the various water parameters. They would simply measure TDS as a proxy for how much "stuff" was added to your pool and then dump water accordingly. The use of TDS is out dated and of no practical value.

    And that's the beauty of TFP. Unlike your neighbor's that follow pool store advice and constantly dump water all the time, you save money on not having to do that.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Mod Squad tim5055's Avatar
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    Re: fiberglass pool water change question

    Matt's got it right. No need to change it.

    Just test at appropriate times and add what the pool needs. There is no automatic "need" for new water.
    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: fiberglass pool water change question

    Thanks for the replies .. Water looks and feels just fine. Something about the age of the water just creeps me out.
    15k gal inground Viking fiberglass pool; Hayward Variable 1.5hp pump (Maxflo VS); Hayward swimclear 325 sg ft cartridge filter; Raypak 206A 199k btu nat gas heater; Aquabot Bravo robotic pool cleaner

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    Re: fiberglass pool water change question

    How much rainfall do you get annually? Multiply that times 4 and you will find that you have likely replaced all the water through rainfall.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: fiberglass pool water change question

    Quote Originally Posted by duraleigh View Post
    How much rainfall do you get annually? Multiply that times 4 and you will find that you have likely replaced all the water through rainfall.
    Rainfall varies (I'm located about 20mi south of Bflo NY) Pool has been closed in Oct each year with a mesh type safety cover so from mid Oct to late April/early May the water level rises due to rain and snow. Every spring when opening we need to pump off at least 6in of water. I suppose I've had to lower the pool level due to rain my 6-8 times in 4 yrs usually i need to add some water to make up for evaporative losses from late spring till fall
    15k gal inground Viking fiberglass pool; Hayward Variable 1.5hp pump (Maxflo VS); Hayward swimclear 325 sg ft cartridge filter; Raypak 206A 199k btu nat gas heater; Aquabot Bravo robotic pool cleaner

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    JoyfulNoise's Avatar
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    Re: fiberglass pool water change question

    Quote Originally Posted by echo View Post
    Rainfall varies (I'm located about 20mi south of Bflo NY) Pool has been closed in Oct each year with a mesh type safety cover so from mid Oct to late April/early May the water level rises due to rain and snow. Every spring when opening we need to pump off at least 6in of water. I suppose I've had to lower the pool level due to rain my 6-8 times in 4 yrs usually i need to add some water to make up for evaporative losses from late spring till fall
    Your water is definitely not "old".

    Where I live (Tucson AZ), we get about 100" of net water loss every year. So an average pool here, left uncovered, will pretty much evaporate away all of the water in it. So in that way, I'm lucky....I get "new" water all the time
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Shekkie's Avatar
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    Re: fiberglass pool water change question

    All water is "old" water. With the filtration and treatment your "recycled" water is good to go. Why start over?
    33k(ish) gallon, IG, vinyl liner, Pentair IC60 SWG, Pentair Triton II sand filter, 1.5hp Pentair VS pump (SuperFlo), Sta-Rite (Pentair) 400K BTU heater (LP), (2) Pentair LED spa lights, TF-100 test kit w/speed stir

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