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Thread: Very high CH and a scale problem

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    Very high CH and a scale problem

    Our pool was filled in late May, and the PB noticed blotchiness in the pebble finish so he drained the pool and performed an acid wash. The finish was perfect for a short time, but by the end of June it was blotchy again. The PB and the finish manufacturer's rep have identified the problem as scale. The pH was consistently over 8.0 and the CH in the 550 - 650 range, both of which have prevented the beginning of treatment with Jack's Magic #2. We've since gotten the pH down to 7.4, but the CH is stubborn and hasn't been lowered despite multiple attempts. The incoming water is 70 ppm calcium, so the source isn't the water we don't think. Plus, it poured down rain all last night (over 2 inches) and the CH is still 550 today. Is it possible that calcium leaching from the pebble finish is causing the CH and scale problems?

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    Re: Very high CH and a scale problem

    Welcome to the forum.

    CH doesn't get in by itself. CH of 70 in your fill water wont build that high in that short of time span.

    What's left? You could be chlorinating heavily with Cal-hypo or it could be coming from your walls. If you are not using Cal-Hypo, the walls are about the only possibility.

    What sort of testing has been done since May?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Very high CH and a scale problem

    Quote Originally Posted by duraleigh View Post
    Welcome to the forum.

    CH doesn't get in by itself. CH of 70 in your fill water wont build that high in that short of time span.

    What's left? You could be chlorinating heavily with Cal-hypo or it could be coming from your walls. If you are not using Cal-Hypo, the walls are about the only possibility.

    What sort of testing has been done since May?
    Lots of testing - weekly by the pool service, and since last month more frequently by me after I bought a Taylor K-2005-salt kit. Let me know if you would like any of the results. I forgot to mention previously that this is a salt pool. The finish is StoneScapes Tropics Blue by NPT.

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    Re: Very high CH and a scale problem

    Are you chlorinating with Cal Hypo?

    Were you doing your own testing when your CH was 550 and your pH so high.

    I am trying to get a grip on how you discovered this and what you were doing prior.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Very high CH and a scale problem

    We are using a Pentair IntelliChlor IC20 salt generator.
    I am testing, my pool service guy is testing, and the owner of the pool service is testing. We are all getting similar results.
    According to the records from my pool service, the pH has been high since the fill. I have only been aware of the high CH since early October, but I have no experience as a first time pool owner and only then knew to ask about it.

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    Re: Very high CH and a scale problem

    What did they use to chlorinate your pool before they started the salt? Tabs in a floater?
    I would consider a partial drain. Take out 1/2 the water and see that the CH is. Then wait a couple of weeks keeping your Ph in the 7.2 to 7.5 range by testing twice per day. What is the TA?

    That is a huge increase in CH to be coming from plaster alone in that short of time.
    22k gallon IG pebblefina, Jandy 1.5 HP VS, Jandy CV Cartridge filter, Fafco solar panels, Polaris 360 supply side cleaner, waterfall

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    Re: Very high CH and a scale problem

    I will add that I became more deeply involved when, after 3+ months of seemingly no progress removing the scale and improving the finish, I did a lot of research to step up my knowledge. Upon my seasonal arrival I began testing the water and I convened a meeting of the PB, Pool Service (PS), and Finish Mfr. to discuss an enhanced approach. The PS had performed the Jack's Magic treatment back in August, but I am now convinced that the water chemistry prerequisites weren't met (pH 7.0-7.4; CH 200-400 ppm; CYA <70; FAC & TAC 1-3 ppm) which led to an unsuccessful attempt. All of those measures are now in line, save for the CH that we are now trying to lower via the addition of sodium bicarbonate. If that is unsuccessful by Monday, the PS will drain some of the pool and we will refill.

    - - - Updated - - -

    Another update following a discussion I just had with my PS and two quick retests... every time the pool has been filled (once) or re-filled (twice) it has been done via the hose bib nearest the pool, the output of which is testing at 580 CH. The hose bib farthest from the pool but at the city water inlet is testing at 70 CH. We will drain on Monday and refill from that bib.

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    JoyfulNoise's Avatar
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    Re: Very high CH and a scale problem

    First off, I have a CH of over 800ppm and I get no scale in my pool. So while 550ppm is not the best, it can be managed with proper adjustments to your pool chemistry and without having to add extra sequestrants to the water. If you post a full set of water results, we can help guide you. So far all we know is that your water has high CH but you have not provided pH, TA, FC/CC, salt and CYA values. All of those are important to proper water balance. Also, unless your house has both well and city water (highly unusual as most municipal water suppliers require private wells to be capped before they will hook up), there is absolutely no reason why one hose bib should read 70ppm and the other 580ppm. This would more likely point to some kind of testing failure.

    Draining and refilling your pool without first understanding all aspects of the water chemistry is only a recipe for continued frustration. Please post a full set of test results from your Taylor kit. You mentioned you had a K-2005. That kit is ok but it does not have the more accurate DPD-FAS chlorine test. You should get the reagents for that or purchase a K-2006 as that is the more advanced test kit.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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