Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 9 of 9

Thread: Low CH but CSI in range ... dangerous for plaster in rough shape?

  1. Back To Top    #1

    Join Date
    Jul 2015
    Location
    Orlando, FL
    Posts
    27

    Low CH but CSI in range ... dangerous for plaster in rough shape?

    Hi folks,

    My water looks amazing now thanks to what I have learned here. Today's readings just before adding liquid Cl:

    FC 5.5
    pH 7.8
    TA 90
    CH 150
    CYA 45 (after *four* water replacements, ugh!)

    So my CSI according to poolMath is around 0.09 which is in range. But CH seems like it shouldn't be @ 150 like mine. Now, my diamond brite (or whatever it is) is in terrible shape, coming off and every time I clean my cartridge it's full of "diamonds". We know it needs to be redone but we're not quite ready yet. My question is ... with the surface in bad shape, should I go higher on CH to protect it till we can refinish or what?
    8,000gal IG w/pebble, screened in, solar heated, including spa. Hayward cartridge filter.

  2. Back To Top    #2
    Casey's Avatar
    Join Date
    Apr 2007
    Location
    SW PA
    Posts
    10,157

    Re: Low CH but CSI in range ... dangerous for plaster in rough shape?

    Welcome to TFP.

    You should add some Calcium to your pool. Also, your pH is on the high side. That needs to come down before you add it to the pool or you'll make it cloudy.

    Check out Pool School and read the ABC's of pool water in my signature link to get a feel on what you should be doing to take care of *your* pool.
    I'd bet you my bikini you'll never get TFP water from a pool store!

    24' Sharkline Venture De Filter

  3. Back To Top    #3
    wjr75's Avatar
    Join Date
    Jun 2013
    Location
    IL
    Posts
    816

    Re: Low CH but CSI in range ... dangerous for plaster in rough shape?

    I think you want your calcium at around 250 otherwise it will suck it out of your plaster. I have a newer finish last year and I add it in the spring to bring it up. My fill water every spring is only 150.
    Inground 22k gallon gunite 15x31 main pool, 15x7 wading pool/sunning deck, hot tub/with overflow (9' octagon with limestone top) & slide NSWG, Aqua Blue Pebble Sheen
    Filter dual cartridge Sta-rite 450sq/ft, TF-100 Test Kit
    Heater Raypak 2100 400k btu cupro-nickel exchanger
    Auto pool cover, Polaris 280 auto pool cleaner, Jandy AqualinkRS8 Remote Control System

  4. Back To Top    #4

    Join Date
    Jul 2015
    Location
    Orlando, FL
    Posts
    27

    Re: Low CH but CSI in range ... dangerous for plaster in rough shape?

    Thanks guys ... I'll get it straightened out this weekend!
    8,000gal IG w/pebble, screened in, solar heated, including spa. Hayward cartridge filter.

  5. Back To Top    #5
    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Location
    Tucson, AZ
    Posts
    37,389

    Re: Low CH but CSI in range ... dangerous for plaster in rough shape?

    If you were in Arizona or Texas I would tell you to leave it since the CH will rise over time just due to evaporation. But being in Florida with the rain you get you probably are gonna have to bring it up to be safer.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  6. Back To Top    #6

    TFP Guide
    PAGirl's Avatar
    Join Date
    Jun 2012
    Location
    Central PA
    Posts
    2,388

    Re: Low CH but CSI in range ... dangerous for plaster in rough shape?

    I am thinking .06 is the upper range for CSI.

    CSI Calcite Saturation Index - requires pH, TA, CH, CYA, Temp, uses Borate, Salt
    Less than -0.6 is suggestive of problems for plaster, tile, stone, and pebble pools.
    Greater than 0.6 is suggestive of problems for all pools
    .
    From the bottom of the pool calculator.....
    26' X 52" Intex Ultra Frame. Intex Sand Filter
    26' X 52 Intex Ultra Frame Install
    You can lead a horse to (clear) water, but you can't force him to swim in it!

  7. Back To Top    #7

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

    Re: Low CH but CSI in range ... dangerous for plaster in rough shape?

    +0.06 is fine; It's +0.6 that is close to when we see calcium carbonate scaling in some pools.

    Actually so long as the pH stays at 7.8 there's nothing wrong with the CH at 150 ppm. The main risk of a higher pH is staining from metals, but if there aren't metals in the water then it's not a problem. It's up to you and I wouldn't sweat it either way. pH 7.8 and CH 150 or raise the CH and have the pH target be lower. If your pH tends to rise, then having the higher pH target may be a better sweet spot for a slower rise in pH.

    Remember that it isn't calcium by itself that gets dissolved from pool plaster but calcium carbonate. Carbonate is in TA and at higher pH there is more of it so having a lower calcium and a higher carbonate can still saturate the water to help prevent dissolving of plaster.
    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"

  8. Back To Top    #8

    Join Date
    Jul 2015
    Location
    Orlando, FL
    Posts
    27

    Re: Low CH but CSI in range ... dangerous for plaster in rough shape?

    Quote Originally Posted by chem geek View Post
    +0.06 is fine; It's +0.6 that is close to when we see calcium carbonate scaling in some pools.

    Actually so long as the pH stays at 7.8 there's nothing wrong with the CH at 150 ppm. The main risk of a higher pH is staining from metals, but if there aren't metals in the water then it's not a problem. It's up to you and I wouldn't sweat it either way. pH 7.8 and CH 150 or raise the CH and have the pH target be lower. If your pH tends to rise, then having the higher pH target may be a better sweet spot for a slower rise in pH.

    Remember that it isn't calcium by itself that gets dissolved from pool plaster but calcium carbonate. Carbonate is in TA and at higher pH there is more of it so having a lower calcium and a higher carbonate can still saturate the water to help prevent dissolving of plaster.
    I just now saw this after I had added some Calcium, bringing my CH to around 270. I did drop pH to 7.5 before doing so but now it's up to 8.0+ ... is it normal for the pH to raise when you add Calcium?
    8,000gal IG w/pebble, screened in, solar heated, including spa. Hayward cartridge filter.

  9. Back To Top    #9
    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Location
    Tucson, AZ
    Posts
    37,389

    Re: Low CH but CSI in range ... dangerous for plaster in rough shape?

    Adding CH should not really raise the pH. Lower the pH back down.

    Aeration from waterfalls, spa, etc can raise the pH.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •