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Thread: CH and CSI- high CH but CSI negative?

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    CH and CSI- high CH but CSI negative?

    FC=5
    Ph=7.5
    TA=50
    CH=650
    CYA=90
    Salt=3000
    Borate=40
    SWG pool
    13,500 gallons, plaster pool
    Temp=80 (Florida)

    I was concerned about my CH going up (now 650). I read various posts about watching the CSI. With the Pool Calculator, my CSI is like -0.56. So it appears to be at risk for leaching calcium from the plaster. However, if I start plugging in numbers in the calculator, I would have to get the CH up to 1500 to get the CSI out of the "danger" zone to -0.2.

    My pool has been fine for 2 years...no scale, no SWG problems. So, do I worry about leaving the CH "too low" at 650? (...but it seems like this is a a high CH according to the suggested levels)....or do I need to take the CH up even more?

    Thanks for any input!

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    Mod Squad tim5055's Avatar
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    Re: CH and CSI- high CH but CSI negative?

    The formula to determine CSI takes several things into account, not just CH. Play with pH, TA & temperature and you will see changes. If you keep your numbers within our recommendations you will generally not have a problem with CSI.
    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: CH and CSI- high CH but CSI negative?

    If you keep your numbers within our recommendations you will generally not have a problem with CSI.
    I agree wholeheartedly. In fact, if you keep your numbers within our recommendations you will virtually NEVER have a problem with any scaling issues in your pool.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Mod Squad pooldv's Avatar
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    Re: CH and CSI- high CH but CSI negative?

    Hi, welcome to TFP! Please update your signature and location per this attachment, What we need to know to answer your questions
    TFP Moderator
    If TFP helped you or saved you money - Become a TFP Supporter! <--Click here
    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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    Re: CH and CSI- high CH but CSI negative?

    Thank you for input, but I am still confused. The Pool Calculator using the suggested levels of CH of 300 will actually give me a CSI of -0.9.

    Have been doing TFP method for many years, so I understand the basics. However, I have not not had high CH until recently. So, not sure what the "recommendations" are in terms of CH.

    As per my first post, I am keeping the FC=5, CYA=90, Salt= 3000, TA=50, BA=40 (or so)....but the CSI will be very negative until i plug in a CH of almost 1500 on the pool calculator. (..."at risk to plaster" per pool calculator at current level of -0.55)

    So, this is my confusion....do I need to add Calcium to push my CH higher than my current 650 (...which currently gives me a CSI of -0.55 or so)?

    thanks

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    Re: CH and CSI- high CH but CSI negative?

    .....in other words, if the "recommendations" are followed, the CSI is -0.81, which indicates risk for corrosion of plaster (...as it is more negative than -0.6).

    This is what is confusing me. It seems the CH has to be very high (as above...around 1500) to get the CSI closer to 0.

    Thanks!

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    Mod Squad tim5055's Avatar
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    Re: CH and CSI- high CH but CSI negative?

    As I said above, CH is not the only player in the CSI game. Your TA is lower than our recommendations. Just by bringing the TA up to 70 your CSI drops to 0.06 With TA of 70 and bringing the CH down to the high end of our recommendation (350) your CSI is -0.15

    Recommendations for a Plaster SWG Pool

    FC (See chart)
    pH 7.5-7.8
    TA 60-80
    CH 250-350
    CYA 70-80
    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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    Mod Squad tim5055's Avatar
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    Re: CH and CSI- high CH but CSI negative?

    Also, so things can be easier kept in context (like you live out west in a high CH area) can you do us a favor an add your city and state to your profile. This helps us deliver better answers to questions asked.

    Additionally, if you would add the following information to your signature


    • The size of your pool in gallons
    • If your pool is an AG (above ground) or IG (in ground)
    • If it's IG, tell us if it's vinyl, plaster/pebble, or fiberglass
    • The type of filter you have (sand, DE, cartridge) and, if you know, the brand and model of the filter.
    • If you know, please tell us the brand and model of the pump, and mention if is it a two speed or variable speed pump.
    • Date of pool build/install, particularly important if less then a year old.
    • What kind/model of water test kit you are using
    • Other significant accessories or options, such as a spa , SWG, or cleaner

    Thanks
    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: CH and CSI- high CH but CSI negative?

    PH is probably the biggest factor with the CSI. Keep the PH around 7.8 and that should resolve your issues. Warmer water temperature can also help.

    Your TA level is on the low side but should be fine since you are using borates. You could raise the TA to 60-80 which will also raise the CSI.

    Plenty of people deal with CH levels much higher than yours...play with the calculator and see what works for you. The CH level doesn't really have as big of an impact on the CSI as you would think. Raising the PH and TA will give you the biggest gains in the right direction.
    -Brian-
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    Re: CH and CSI- high CH but CSI negative?

    Quote Originally Posted by tim5055 View Post
    As I said above, CH is not the only player in the CSI game. Your TA is lower than our recommendations. Just by bringing the TA up to 70 your CSI drops to 0.06 With TA of 70 and bringing the CH down to the high end of our recommendation (350) your CSI is -0.15

    Recommendations for a Plaster SWG Pool

    FC (See chart)
    pH 7.5-7.8
    TA 60-80
    CH 250-350
    CYA 70-80
    CSI also takes salt, temp and borates into account. With the low end of the recommended levels you end up with a CSI of -0.71:

    PH 7.5
    TA 60
    CH 250
    CYA 70
    Salt 3600
    Borate 50

    It takes a PH of 7.8 to get the number up to -0.56, which is at the top end of the recommended level and very near -0.6.

    His higher CH is actually beneficial for keeping his CSI up.
    -Brian-
    33K Pool/Spa, Pentair Equipment
    POOL BUILD
    Davis Custom Construction - Home Page

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    Re: CH and CSI- high CH but CSI negative?

    Thanks for all the help!

    (I have made a signature, took me a while to figure out where the link for that was).

    Hard to keep TA up with SWG, but I will try.

    Thanks again!
    13,500 gallons, Jandy SWG, single speed pump, Pool built in 2006, Cartridge filter, East Coast of Florida, Plaster in-ground pool, electric heater, TF test kit

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    Re: CH and CSI- high CH but CSI negative?

    Check out this thread by Chem Geek

    http://www.troublefreepool.com/threa...mmended-Levels
    -Brian-
    33K Pool/Spa, Pentair Equipment
    POOL BUILD
    Davis Custom Construction - Home Page

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    Re: CH and CSI- high CH but CSI negative?

    OK...thanks....Chem Geek always to the rescue!

    I will push my TA up some and not worry too much about the negative CSI. At some point, I will drain some water and get the CH down to 300 ish. My fill water is not too bad (about CH of 70), so it would not be too hard to do a 1/2 pool drain / fill at some point.

    Thanks again!
    13,500 gallons, Jandy SWG, single speed pump, Pool built in 2006, Cartridge filter, East Coast of Florida, Plaster in-ground pool, electric heater, TF test kit

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    Re: CH and CSI- high CH but CSI negative?

    A negative CSI is actually what you want in a SWG pool. Your CH level is not a problem where it is now so no need to drain unless you are having other issues.

    How did your CH get that high if your fill is so low? Is the pool really old?
    -Brian-
    33K Pool/Spa, Pentair Equipment
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    Re: CH and CSI- high CH but CSI negative?

    I run high CH (above recommended levels) to maintain proper CSI levels. I run my CSI slightly negative because I have a SWCG. It hasn't needed cleaning because of scale.
    17K Kidney Shaped Pool Concrete (Diamond Bright) Pool, 3/4 hp 2 speed 115V Sta-rite Duraglas PEA5D-180L/P2R5D-181L (Impeller C105-92PS Diffuser C1-216P), 1.5 piping, Pentair CC100 Filter , Heat Siphon 100K BTU Heat Pump Pool Heater, Flow meter Blue White Flowmeter Model No. F-30150P, Hayward Astrolight SP0581N, SWCG CalimarTitanium Edition TE45 , Dolphin Nautilus Plus with CleverClean, Lakeland Florida

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    Re: CH and CSI- high CH but CSI negative?

    Pool is from 2006.

    I moved into this house in 2013, and I do not have any history on any drain/fills and I have not drained pool since I have owned it.

    I checked the CH over a year ago, and I think it was 450 or so. I did not bother rechecking until recently, and never thought much about the CH until now.
    13,500 gallons, Jandy SWG, single speed pump, Pool built in 2006, Cartridge filter, East Coast of Florida, Plaster in-ground pool, electric heater, TF test kit

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