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Thread: Gunite Salt Water Pool PH Problems

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    Gunite Salt Water Pool PH Problems

    I have a new gunite salt water pool that was installed last year and plastered the first week in May of 2012. From May until the time I had the pool closed in late Sept. I battled the PH levels constantly rising because of the plaster curing, which I was told was normal. However, when the pool was opened in May of this year I had a scale problem that was so bad the pool had to be drained and hydro-sanded. The pool installer argued that the plaster was fine and that there must have been a chemical imbalance in the water over the winter. Since I did my own water testing and also had my water tested every other week by 2 different pool stores throughout the season I threw in the towel this year and hired a pool professional to do my maintenance. However, the same problem has been going on again this season. Since June the pool professional has been adding 1 gallon of muriatic acid every other week and for the weeks he is not adding muriatic acid he is adding 4lbs. of PH down. The pool is 18,700 gallons and I have a salt system. My question is whether this is normal and if not what's driving the PH to continue to rise? My concern is also that I will have the same scale problem next season when the pool is opened again. Thanks.

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    Mod Squad jblizzle's Avatar
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    Re: Gunite Salt Water Pool PH Problems

    Welcome to TFP!!!

    Post up a full set of test results, specifically the TA.
    High TA can cause the pH to rise.
    Also, SWG themselves cause the pH to rise.
    Do you have any water features or spill over? Because the aeration caused by them also causes the pH to rise.
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    Re: Gunite Salt Water Pool PH Problems

    Thanks for the quick reply. The pool guy writes down all the levels every week before treatment. Yesterday the PH was 7.8, TA 130, Calcium 250, CYA 30 (low I know), Chlorine 2.0. It's usually always around the same week to week with the PH sometime at 8.0. I still do my own testing w strips and also use a Taylor kit and would say the TA is more like 110 but everything else seems fairly consistent with pool guy readings.

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    Mod Squad jblizzle's Avatar
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    Re: Gunite Salt Water Pool PH Problems

    Well, that TA is higher than we would recommend. Do you have any water features as well?

    Part of your problem is going to be that the advice we give is likely to conflict with what you pool guy is going to do. What test kit do YOU have? Your tests will always be better than a pool store/guy and certainly do not use strips for anything.

    This forum is mostly geared toward homeowners that maintain their own pools and our recommendations generally do not mesh with pool stores or pool maintenance companies.
    Jason, TFP Moderator
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    Re: Gunite Salt Water Pool PH Problems

    I use a Pentair 78DPD test kit and really only use the strips to get a quick read on the Chlorine when I want too and so I can keep the salt generator at a relatively low level. The only other water feature I have is the Nature 2 sytem and I rarely shock the pool. When I have shocked the pool I have used Sodium Dichloride since I'm sensitive to the PH and calcium levels going up and contributing to scale. I prefer doing my own maintenance which is why I joined this forum because even though I have someone doing it for me, I continue to do it as well. I no longer go to the pool store. I just don't understand why there is the constant demand on a weekly basis when the amount of product that's going into the pool should knock down the levels for more than a week. No other water problems. The water is as clear as can be. Thanks.

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    Mod Squad jblizzle's Avatar
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    Re: Gunite Salt Water Pool PH Problems

    It is not uncommon to have to adjust the pH every few days with a SWG ... especially when the TA is too high.

    I think you should do some more reading in Pool School as some of your statements do not make sense.

    - Ditch the Nature 2. It is adding metals which can lead to staining.
    - No one here regularly "shocks" the pool. We go through the SLAM process only IF there is a problem
    - Dichlor adds CYA and is acidic ... not sure how that helps your sensitivities.

    If you want to take control, get one of the Recommended Test Kits (yours is missing the CYA and FAS-DPD chlorine tests) and then Lower your Total Alkalinity and see if the pH rise slows down.
    Jason, TFP Moderator
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    Re: Gunite Salt Water Pool PH Problems

    What I meant by sensitivity is that sodium dychlor is Ph neutral as opposed to other shocks like calcium hypochlorite which is higher in ph and has calcium, thus contributing to increase levels for both.

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    Mod Squad jblizzle's Avatar
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    Re: Gunite Salt Water Pool PH Problems

    All of that is not true. The Dichlor is very acidic when it dissolves and addes CYA. While cal-hypo is nearly pH neutral, but adds calcium.

    You can use the Effect of Adding Chemicals at the bottom of poolcalculator.com to see how each affects the water.
    Jason, TFP Moderator
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    Re: Gunite Salt Water Pool PH Problems

    I add about a gallon of MA each month (for a 9,200 gallon pool), maybe a little more, and my plastered SWG pool is almost three years old. I keep my TA around 70-80 and pH still rises. I've tried to lower it to 60 but with 220 TA fill water it's tough. But MA is cheap and except for topping up the CYA, salt and borax, it's the only chemical I need to maintain my pool.
    9,200 gal. Gunite Luna Quartz French Grey pool with spill over spa, two fountains on tanning ledge (rarely used)
    Pentair Whisperflo 2HP, Pentair CCP Cartridge 420 Sq. Ft., Polaris 280 with booster pump
    Pentair EasyTouch 4, RayPak LoNox 266k Natural Gas heater, Aqua Rite SWCG T Cell 9, Borates, TF-100 test kit

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    Re: Gunite Salt Water Pool PH Problems

    Thanks. The amount of MA for my pool doesn't seem that unreasonable now. Were your levels harder to maintain the first or second year and/or did you have any scale problems? My pool is closed 8 months if the year since I'm in NJ.

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