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Thread: Question on lowish CH

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    vcarnett's Avatar
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    Question on lowish CH

    Good morning,

    After a recent drain/refill, I've been concerned about my CH @ 140ppm (now lower, 120, I'm assuming due to rain - ~2" - as I've had no top offs since that reduction). However, after much reading here today, I've been educated on CSI (I previously ignored that section in the calc) and the fact that my CH will rise as I top off due to evaporation (this I also learned from reading here today: CH does not evaporate and the resulting top-off adds whatever CH is in the tap). Thank you TFP experts!

    Sooooo, Since my CSI is -.35 and other #'s are looking good, I'm thinking (here I go thinking again - PLEASE correct me if I'm off) I shouldn't worry about the 120ppm CH. We usually have high evaporation and my fill (from outside tap - city water) is 50ppm CH (I was quite surprised at this as I'm in Austin - limestone - and we're known for very hard water) so it should rise over the summer. Again, if I'm understanding correctly, since my CSI is in the safe range I shouldn't have to worry about my pool water pulling calcium from any other source.

    Current readings:
    FC 5.2
    pH 7.5
    TA 80
    CH 120
    CYA 30 (I should note that I currently have several 3" pucks in the in-line chlorinator just to raise CYA. I will remove once it comes up a little - I normally use only bleach to chlorinate)
    CC 0
    CSI -.35

    p.s. my next inquiry will be to the city to see if maybe they're now using reverse osmosis or some such to treat the water as I was amazed at the 50ppm CH reading from tap - we don't have a water softener (besides, the outside taps' source should be from the water that has not yet entered the softener - from the line between the city tap and the softener)
    Anthony Sylvan 17k gal free form IG Gunite. 3' - 6'. Waterway SVL56 Pump. Pentair FNSP 48 (sq ') DE Filter (2013). Polaris 280 sweep w/Polaris PB4 booster. 2 skimmer intakes and 2 deep-end intakes. 4 returns. Pool Installed 2010. Filled from city water (Austin, TX - CH 50ppm. pH 9.0). Taylor k-2006 test kit. Currently running the pump 6 hrs / day.

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    Mod Squad JVTrain's Avatar
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    Re: Question on lowish CH

    I'd stick with a wait and see approach. As you know from playing with Pool Math, pH can have a very immediate and drastic effect on CSI. At that CH level, as long as you let your pH linger in the upper range, 7.5-7.8, most of the time your CSI will be fairly neutral. In Austin, I'd consider adding 10 ppm more CYA to curb your chlorine consumption for sure. This will make your CSI VERY slightly more negative but not a significant amount to be concerned with. That low CH can be managed easily with pH control and give you leeway if your CH starts to climb over the long term.
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
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    vcarnett's Avatar
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    Re: Question on lowish CH

    Just returned from pool store. They read my cya at 30 so I feel better. I want to give it a few days to see what the 11 pucks have on cya (4 in the skimmer and 7 in-line). Will check fc daily.
    Anthony Sylvan 17k gal free form IG Gunite. 3' - 6'. Waterway SVL56 Pump. Pentair FNSP 48 (sq ') DE Filter (2013). Polaris 280 sweep w/Polaris PB4 booster. 2 skimmer intakes and 2 deep-end intakes. 4 returns. Pool Installed 2010. Filled from city water (Austin, TX - CH 50ppm. pH 9.0). Taylor k-2006 test kit. Currently running the pump 6 hrs / day.

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    vcarnett's Avatar
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    Re: Question on lowish CH

    I want to give it a few days to see what the 11 pucks have on cya (4 in the skimmer and 7 in-line). Will check fc daily.
    I meant to pose that as more of a question. What do you think 11 pucks and let's say, 1 week, do to the cya #? Should I just go ahead and add stabilizer to get it up to 40 more quickly?
    Anthony Sylvan 17k gal free form IG Gunite. 3' - 6'. Waterway SVL56 Pump. Pentair FNSP 48 (sq ') DE Filter (2013). Polaris 280 sweep w/Polaris PB4 booster. 2 skimmer intakes and 2 deep-end intakes. 4 returns. Pool Installed 2010. Filled from city water (Austin, TX - CH 50ppm. pH 9.0). Taylor k-2006 test kit. Currently running the pump 6 hrs / day.

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    Mod Squad jblizzle's Avatar
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    Re: Question on lowish CH

    You can use the "Effects of Adding Chemicals" part of PoolMath to tell you how much CYA those pucks will add.
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    vcarnett's Avatar
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    Re: Question on lowish CH

    You can use the "Effects of Adding Chemicals" part of PoolMath to tell you how much CYA those pucks will add.
    Oh thanks! I hadn't even noticed that section. OK, I'm assuming Trichlor = Trichloro-s-trianzinetrione (Leslie's pucks).

    Here's my thought - please tell me if I'm on right track: If I only used 5 pucks that would reach my target of adding 10ppm CYA. However, I don't like what it does to pH (lowers by 0.86). IF this were a normal season it would be OK as I would be topping off with high pH (9.0) fill. However, we've been getting a lot of rain so no need for top off.

    So, I'm thinking I need to yank the pucks and just add stabilizer as it has a much gentler effect on pH.

    thoughts?

    Thanks!
    Anthony Sylvan 17k gal free form IG Gunite. 3' - 6'. Waterway SVL56 Pump. Pentair FNSP 48 (sq ') DE Filter (2013). Polaris 280 sweep w/Polaris PB4 booster. 2 skimmer intakes and 2 deep-end intakes. 4 returns. Pool Installed 2010. Filled from city water (Austin, TX - CH 50ppm. pH 9.0). Taylor k-2006 test kit. Currently running the pump 6 hrs / day.

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    Patrick_B's Avatar
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    Re: Question on lowish CH

    You can, and save the pucks for vacations and such. I'm a little surprised at 50 near Austin, but it varies down there. Not close, but my buddy in Lavernia has softer than that. Your hardness gives you the option of using Cal-Hypo as well. At least sometimes. No problem with that if you manage it right.
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    vcarnett's Avatar
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    Re: Question on lowish CH

    OK great. Thanks. Yes, I was very surprised to find 50. In fact, I will test again as I'm just having a hard time believing. Installed water softeners have always been a big selling point here.

    From my reading on this site: I'm thinking CH of 120 should be OK as long as I keep the pH in higher range (7.5 - 7.8). Also considering that SURELY it will get hot/dry again and I'll be topping off, which will raise that (just read that here today - that evap does not reduce CH, but, of course, top offs raise).

    Loving this site. I laughed to myself when the pool store guy tried to sell me Phosfree and again when he shook his head in dismay when I told him that I use household bleach to chlorinate.

    Thanks again. cheers
    Anthony Sylvan 17k gal free form IG Gunite. 3' - 6'. Waterway SVL56 Pump. Pentair FNSP 48 (sq ') DE Filter (2013). Polaris 280 sweep w/Polaris PB4 booster. 2 skimmer intakes and 2 deep-end intakes. 4 returns. Pool Installed 2010. Filled from city water (Austin, TX - CH 50ppm. pH 9.0). Taylor k-2006 test kit. Currently running the pump 6 hrs / day.

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