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Thread: Numbers Post-SLAM - What is the effect of low CH?

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    Numbers Post-SLAM - What is the effect of low CH?

    Having successfully completed my SLAM last week, I have been focused on monitoring the FC this last week to determine how much I lose each day. Target is to maintain FC between 5 and 7 (CYA 60) and that has been going well. I am losing about 2ppm FC per day so adding 41oz 8.25% bleach to regain that loss.

    Today I did my first full set of tests since my SLAM and results are:

    pH: 7.7
    FC: 6.5
    CC: 0.0
    CH: 225
    TA: 80
    CYA: 60

    Plan of adding a pint of muriatic acid to bring pH to 7.4 - Both my grand daughter and I have had some stingy eyes which I am attributing to slightly high pH?

    I think everything else is good except the CH is a little low. Curious what the impact is of low CH? According to pool math I need to add 207oz of calcium chloride to bring CH to 300 (targeting midway on the recommended range of 250 to 300). Is there any reason to target higher or lower than that? Also where so I purchase calcium chloride and what name is it sold under?

    Thanks
    Dave
    In Ground Gunite with PebbleTec finish, 16.5ft x 35ft, 18600 gallons
    Elevated Spa with spillway
    Pentair Cartridge Filter, Pentair Pumps and Controller
    TF-100 Test Kit
    Located in Katy, TX

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    Mod Squad zea3's Avatar
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    Re: Numbers Post-SLAM - What is the effect of low CH?

    300ppm is a good number to target. You can find Calcium Chloride in road de-icer, however you may have difficulty finding it in Katy in the summer! Any calcium increaser for pools will work. Go to your local Walmart or other big box store and look for calcium increaser in their pool aisle. They will probably have the cheapest prices around here.
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    Re: Numbers Post-SLAM - What is the effect of low CH?

    Quote Originally Posted by zea3 View Post
    300ppm is a good number to target. You can find Calcium Chloride in road de-icer, however you may have difficulty finding it in Katy in the summer! Any calcium increaser for pools will work. Go to your local Walmart or other big box store and look for calcium increaser in their pool aisle. They will probably have the cheapest prices around here.
    Thanks - I always seem to be in Walmart for something every weekend Guess I will be heading there this weekend too lol
    In Ground Gunite with PebbleTec finish, 16.5ft x 35ft, 18600 gallons
    Elevated Spa with spillway
    Pentair Cartridge Filter, Pentair Pumps and Controller
    TF-100 Test Kit
    Located in Katy, TX

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    Texas Splash's Avatar
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    Re: Numbers Post-SLAM - What is the effect of low CH?

    Hi Dave. A low CH means that the water doesn't have enough hardness to it, so where will it get it?....... from your plaster. So a low CH can begin to dissolve, etch, or erode your plaster. A high CH has the opposite effect where it causes scaling. That's why we watch the CSI row on the Poolmath calculator closely. If you have hard water in your area, you might opt to keep the pH and/or TA slightly elevated to compensate for a low CH until the fill water increases it from refills after evaporation. For those who have exceptionally soft water, then yes, they would want to add some products to increase CH.

    Calcium hardness can be raised with calcium chloride or calcium chloride dihydrate. They are available in some areas as Peladow, Dowflake, Tetra Flake, or Tetra 94, often sold as a deicer by hardware stores, and some big box stores, in colder climates. Pool stores will carry either calcium chloride or calcium chloride dihydrate under a variety of names, including Hardness Plus, Balance Pak 300, Calcium Hardness Increaser, etc. Calcium products should be spread across the surface of the deep end of the pool.

    Does that help?
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    Re: Numbers Post-SLAM - What is the effect of low CH?

    Quote Originally Posted by Texas Splash View Post
    Hi Dave. A low CH means that the water doesn't have enough hardness to it, so where will it get it?....... from your plaster. So a low CH can begin to dissolve, etch, or erode your plaster. A high CH has the opposite effect where it causes scaling. That's why we watch the CSI row on the Poolmath calculator closely. If you have hard water in your area, you might opt to keep the pH and/or TA slightly elevated to compensate for a low CH until the fill water increases it from refills after evaporation. For those who have exceptionally soft water, then yes, they would want to add some products to increase CH.

    Calcium hardness can be raised with calcium chloride or calcium chloride dihydrate. They are available in some areas as Peladow, Dowflake, Tetra Flake, or Tetra 94, often sold as a deicer by hardware stores, and some big box stores, in colder climates. Pool stores will carry either calcium chloride or calcium chloride dihydrate under a variety of names, including Hardness Plus, Balance Pak 300, Calcium Hardness Increaser, etc. Calcium products should be spread across the surface of the deep end of the pool.

    Does that help?
    Thanks for the reply, yes definitely helps. You actually prompted me to test my fill water, I have always thought we had hard water but never actually tested it.

    Results of testing the fill water:
    CH: 100
    TA: 220
    pH: 8.2+

    Was wondering if I could just wait till I need to top up and rely on fill water to bring the CH up? But that said, I haven't had to fill up but once since the beginning of May since we have had so much rain!

    Looks like I need to bring the CH up to avoid any potential problems with the plaster (sure don't want that) so plan on buying some hardness increaser and going that route!

    Thanks
    Dave
    In Ground Gunite with PebbleTec finish, 16.5ft x 35ft, 18600 gallons
    Elevated Spa with spillway
    Pentair Cartridge Filter, Pentair Pumps and Controller
    TF-100 Test Kit
    Located in Katy, TX

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