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Thread: Attached SPA impact on Pool Chemistry

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    Esloser's Avatar
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    Attached SPA impact on Pool Chemistry

    Just curious... how does an attached SPA impact the rest of the pool's chemistry. I have a 6 jet attached spa that overflows into the pool when not in SPA Mode. I'm wondering how it impacts the pool chemistry - PH, FC, etc. with the water getting heated to 94-100 degrees and blowing air through it.

    Eric
    36,000 Gallon Inground (IG) Gunite Pool with Spa and 12" tanning ledge | White Plaster | Cartridge Filter | Hayward Single Speed Pump (x2) | 400k BTU Hayward Heater | Hayward ProLogic Automation | Taylor K2006 Test Kit | In-pool Cleaner | August / September 2016 Build Date | Build Thread

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    Richard320's Avatar
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    Re: Attached SPA impact on Pool Chemistry

    The aeration drives pH up. Otherwise, there's no real difference between one giant pool and a pool with a spillover spa of the same gallonage.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    foobert's Avatar
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    Re: Attached SPA impact on Pool Chemistry

    Aeration will tend to raise you PH.

    Temperature has a minor effect on CSI values (you can see change in the Pool Math). Othewise, it's not much different than having well used and splashed in pool.
    ~john
    24.5K G, pebble, SuperFlo VS 1.5, 48sq DE filter, Hayward H250FDN, Autopilot RC-52, Poolvergnuegen & 3 daily swimmers in season.

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    Esloser's Avatar
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    Re: Attached SPA impact on Pool Chemistry

    I guess that helps explain why I go through so much Muriatic Acid - usually 2-3 gallons per week. It's also a new pool, so I have that working against me too. What about FC? Does warmer water use FC faster than the cooler water of the pool?
    36,000 Gallon Inground (IG) Gunite Pool with Spa and 12" tanning ledge | White Plaster | Cartridge Filter | Hayward Single Speed Pump (x2) | 400k BTU Hayward Heater | Hayward ProLogic Automation | Taylor K2006 Test Kit | In-pool Cleaner | August / September 2016 Build Date | Build Thread

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    Richard320's Avatar
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    Re: Attached SPA impact on Pool Chemistry

    Quote Originally Posted by Esloser View Post
    I guess that helps explain why I go through so much Muriatic Acid - usually 2-3 gallons per week. It's also a new pool, so I have that working against me too. What about FC? Does warmer water use FC faster than the cooler water of the pool?
    I couldn't say for sure. I only run the heater when I'm using the spa, and then I only heat the spa. A spa-load of water at 100 is only going to raise the rest of the pool 1 or 2 degrees. Not enough change to make a noticeable change in FC, I doubt.

    When I use the spa, I start my drawing the water down a few inches, so that when we get in, it doesn't overflow. Why heat it just to push it out? Then I set it to spa only and fire up the heat. There's less water to heat since it's already been lowered. Heats faster. I also don't like the blower and I restricted the air intake to the venturis. Why heat water and then blow cold air in it to cool it off? When we're done, I kill the heater and switch the valves and let it fill and spill out.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Esloser's Avatar
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    Re: Attached SPA impact on Pool Chemistry

    Do you draw from the pool at all when using the Spa? I was thinking of cracking open the pool suction line to pool a little bit of pool water into the spa to trickle it over the spillway. That way, if someone gets out, the spa will slowly return to the right water level. I haven't tested my theory yet.
    36,000 Gallon Inground (IG) Gunite Pool with Spa and 12" tanning ledge | White Plaster | Cartridge Filter | Hayward Single Speed Pump (x2) | 400k BTU Hayward Heater | Hayward ProLogic Automation | Taylor K2006 Test Kit | In-pool Cleaner | August / September 2016 Build Date | Build Thread

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    Richard320's Avatar
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    Re: Attached SPA impact on Pool Chemistry

    There's only the two of us that use the spa, so an inch or so is no big deal. When I have the heat on in the spa, I only want to heat the water in the spa and no other. Drawing from a cooler pool will just chill the spa.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Attached SPA impact on Pool Chemistry

    I too have attached spa. Last time we used spa legs itched. Here are my numbers.
    Unheated FC 5 PH 7.4 TA 90
    Heated to 99 FC 5 PH 8.0 TA 90
    How low can I keep the PH in my pool so the heated spa PH is not so high?
    20k gallon IG pool & spa, pebble, Aquapure PLC1400 SWG
    Jandy DE filter mod # DEV60, Raypak 399k BTU heater
    Jandy pumps, 2.0 hp for pool, 1.5 hp for spa
    Polaris cleaner, 2' sheer descent

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    Richard320's Avatar
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    Re: Attached SPA impact on Pool Chemistry

    Quote Originally Posted by windyknollsva View Post
    I too have attached spa. Last time we used spa legs itched. Here are my numbers.
    Unheated FC 5 PH 7.4 TA 90
    Heated to 99 FC 5 PH 8.0 TA 90
    How low can I keep the PH in my pool so the heated spa PH is not so high?
    It's not the heat. Heating the water should lower pH PH levels

    The spa is probably churning with bubbles and aeration drives the pH up. When I attacked my high pH with acid & aeration, I let the spa run full bore and drove the whole pool's pH up from 7.2 to 7.6 in about 4 hours. You might find that lowering the TA in the whole system will slow the pH rise in the spa. I don't care much for all the froth and I don't see any point in heating the water only to cool with cold air, so I don' run the blower and covered the venturi intake so I just get hot water.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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