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Thread: OK, where did this calcium come from?

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    chiefwej's Avatar
    Join Date
    Jun 2011

    OK, where did this calcium come from?

    I was planning on having an RO treatment done to reduce my CH level, which had gotten over 1,000. The local company after giving the run around for a month called last week and said the pump was out on their equipment. They would have to reschedule, date unknown.

    I tested my tap water (as the CH varies time to time) and the current CH was 150. So, I decided on a full drain and refill. I fully drained the pool and rinsed it down (didnt pressure wash or acid wash) and refilled the pool. There was no perceptible scale on the pool. I added my chemicals, 400 lb salt, 10 lb CYA, 14 boxes of borax, and 4 gallons of muratic acid to rebalance pH. Time to do a full battery of tests on my new water.

    Now I do all my tests and my water has a CH of 250. How did it go from 150 at the tap to 250 in the pool?

    I could see it going up if there were a lot of scale on the pool and/or I had the CSI negative for some time. But, neither is true and the water has only been in the pool a couple days.
    Tucson, AZ
    16x36 rectangular (19k) Pebble Tec play pool/spa, Pentair Intelliflo VS 011018, Super II 2hp (spa), Aqua Rite T-15 SWG, Pro Grid 60 DE, H400 & Heliocol Solar, Dolphin S-300, fill water w/high CH and TA, 50 ppm borates,TF-100 test kit, Smart Home/Alexa pool control

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    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: OK, where did this calcium come from?

    Since you didn't put any in (except for the 150 in your fill), it had to already be there. Most likely precipitated onto the walls which didn't get fully cleaned and then dissolved back into solution.

    Regardless, it is there and it will probably continue to slowly increase.

    Testing error possibility always exists but probably not nearly that much.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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