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Thread: Low TA, High CH required?

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    Low TA, High CH required?

    I've had this spa a little over 2 years. My TA runs around 35 to maintain a good PH around 7.6. Of course on poolcalc my CSI is kinda far into the negative - around -4.

    The water starts with a CH of around 80 and I've always just bumped it to 150 and left it there, but now I'm wondering if I shouldn't raise the CH to around 300 - which should give me a CSI of near 0.

    So I'm just looking for a sanity check - does this plan make since?

    Thanks all!

    -Chak
    290 Gallon fiberglass reinforced acrylic spa
    Cartridge filter
    Above Ground
    2 x 5HP pumps - unknown flow rate.
    Ozonator
    --------------------------------------------
    6800 Gallon 17' x 48" Vinyl above ground pool (Summer Escapes)
    Intex 2650 Sand Filter

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    JasonLion's Avatar
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    May 2007
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    Re: Low TA, High CH required?

    There is no point in taking CSI all the way up to zero. If you really meant -4.0 then yes that is way to low, but -0.4 is fine.

    The recommended CH level for fiberglass is 220 to 320. In fiberglass it doesn't make nearly as much difference as it does with plaster, but it can help the gel coat last longer.
    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

  3. Back To Top    #3

    Re: Low TA, High CH required?

    Cool - it does say the -.6 is indicative of problems - but not for fiberglass, just stone based linings.

    That said, if 220-320 is best for fiberglass, then perhaps I should go for the CH of 300.

    I have to be honest - I don't think the material is fiberglass, but its definitively man made.

    On a side note, I don't use Borates and I don't like them. It makes the bubbles pop/splash my face. I'm also trying this fill with no CYA's just to see how things go.
    290 Gallon fiberglass reinforced acrylic spa
    Cartridge filter
    Above Ground
    2 x 5HP pumps - unknown flow rate.
    Ozonator
    --------------------------------------------
    6800 Gallon 17' x 48" Vinyl above ground pool (Summer Escapes)
    Intex 2650 Sand Filter

  4. Back To Top    #4

    Re: Low TA, High CH required?

    If the tub is fiberglass, then the CSI does help. However, if your tub's surface is acrylic, then you really don't need to worry about the CSI.

    Going to 300 on the calcium would most likely scale the heater.

  5. Back To Top    #5

    Re: Low TA, High CH required?

    Ok, so is there a downside to higher CH? I realize a lot of people aren't lucky like me in having a fairly low CH water source.

    I would guess it is acrylic - there is a 1/8" thick colored textured layer of what looks like plastic over a white/gray base of about 3/8" thickness.
    290 Gallon fiberglass reinforced acrylic spa
    Cartridge filter
    Above Ground
    2 x 5HP pumps - unknown flow rate.
    Ozonator
    --------------------------------------------
    6800 Gallon 17' x 48" Vinyl above ground pool (Summer Escapes)
    Intex 2650 Sand Filter

  6. Back To Top    #6

    Re: Low TA, High CH required?

    Quote Originally Posted by Chakara
    Ok, so is there a downside to higher CH?
    The water temperature in the heater can be substantially hotter than the rest of the water, which increases the CSI in the heater. Increasing the calcium to 300 would risk calcium scaling damaging the heater.

  7. Back To Top    #7

    Re: Low TA, High CH required?

    Cool - then a CSI of -0.4 with a CH of 150 it shall be. Does make me wonder if I should leave my CH at the fill water level of 80 though, but running in the calc, even if the heater is at 200 degrees (much more and it would boil the water), my CSI is @ .36 - so it swings from -0.3.x to +0.3.x - IE: perfect

    Thanks for the feedback guys!

    -Chak
    290 Gallon fiberglass reinforced acrylic spa
    Cartridge filter
    Above Ground
    2 x 5HP pumps - unknown flow rate.
    Ozonator
    --------------------------------------------
    6800 Gallon 17' x 48" Vinyl above ground pool (Summer Escapes)
    Intex 2650 Sand Filter

  8. Back To Top    #8

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Low TA, High CH required?

    The temperature of the heat exchanger water pipe in the heater is probably around 30F hotter than the spa water, so perhaps 134F or so.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  9. Back To Top    #9

    Re: Low TA, High CH required?

    If the heater is an electric element, it will radiate about 5,000 watts. I'm not sure how hot it gets, but it will get quite hot.

  10. Back To Top    #10

    Re: Low TA, High CH required?

    Hm - I can see where the element would get quite hot - but it also has a fair amount of flow over it. I would think that at the very surface of the heater element would be much hotter than even .1 inches away.

    I don't know if the spa pack runs the water for a while after it turns off the heating element - as that could be another factor.

    All said, I think I'll be OK with a -0.3x CSI. Unless one of you guru's think it is wiser to have a higher CH, for a lower CSI.

    -Chak

    PS: once again, thank you all for this site and your advice. I don't know how people survived before the internet
    290 Gallon fiberglass reinforced acrylic spa
    Cartridge filter
    Above Ground
    2 x 5HP pumps - unknown flow rate.
    Ozonator
    --------------------------------------------
    6800 Gallon 17' x 48" Vinyl above ground pool (Summer Escapes)
    Intex 2650 Sand Filter

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