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Thread: How do you test a SWC to see if it's working properly?

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    swimcoachtdawg's Avatar
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    How do you test a SWC to see if it's working properly?

    I've had on and off problems with my SWC over the 8 years since it was built. Here is what is happening currently: about three weeks ago, I went without checking chemicals for about two days. We were busy, and I didn't even go out to the pool, since my team is not using it but two days a week right now. When I went to take the cover off (we keep a solar cover on it in the winter to help hold the heat in and keep the moisture down inside the building when it's closed up). and it was GREEN. I mean green and you couldn't see the bottom at all. Checked the chlorine and of course it was 0. So I spent the next few days slamming and getting the pool back in balance. It seemed like it took a long time to get the chlorine up to slam level, and over 5 gallons of bleach.

    So the entire time this was going on, the the Mineral Springs system was on, and supposedly generating chlorine. I had it turned to about 32, which had worked well all summer. Being the analytical sort I wanted to know why this was suddenly not working and things took such a major turn for the worse in such a short time. One week before, I had put the cover on for the first time since the spring, so I thought maybe the cover had developed some algae and transferred it to the pool. Even so, usually in the winter, with the cover on, I have to turn the SWC generator down to keep the chlorine from getting too high, since we don't lose much water to evaporation when the cover is on, therefore keeping the chlorine in the pool.

    One week later, the chlorine had dropped again, not to 0 again, but it was below 3.0, which has never been good in my pool, I've always had to keep it above 5.0. When the problem happened the week before, I turned the SWC up to 60. I put another 3 gallons of chlorine in the pool manually, and have been monitoring it ever since. Today all the numbers are good, as I've listed below, but it seems to me that with the SWC set at 60 I should have WAY too much chlorine in the pool now, and I don't. The SWC readings are listed below too. It looks like it's working fine, I am getting no error messages or indications that it's not working. My question is, how do I test it to see if it's really working?

    Here are my current settings:
    Mineral Springs
    3300
    78 (my pool heat is off at the moment, so the temp has dropped)
    25.9
    6.04
    60P
    -3100
    AL-0
    r1.58
    t-15

    Chemicals:
    Cl 5+
    pH 7.6
    Cl drop test FC 10 Chloramines .5 = TC 10.5
    CH 200
    TA 100
    CYA 90

    NaCl test kit:
    2800

    Any help would be appreciated. I tried going to the Mineral Springs website and the manual for the unit and none of them were helpful. Thanks!
    75'X12' 2-lane IG lap pool built in 2008. 33,000 gallons. Gunite construction with vinyl liner. All equipment is Hayward - cartridge filtration system, Mineral Springs SWG (not currently working - switched to adding chlorine manually), 300,000BTU natural gas pool heater. Also use a 4-panel solar system in summer. Pool is located inside a 25'X100' concrete block building w/natural gas forced air furnace/SIPS roof.

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    Re: How do you test a SWC to see if it's working properly?

    If the volts, amps and salt level are correct, it's working correctly. All of your numbers look good. Periodically, check the diagnostics to see if the numbers get off track.

    Are you sure about that salt test? An 8 year old cell will usually begin to decline in performance, which causes the box salt reading to be lower than actual.

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    swimcoachtdawg's Avatar
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    Re: How do you test a SWC to see if it's working properly?

    I've already replaced the cell once, this one is just over three years old. My concern is that, with the unit set at 60% I should not be having to add chlorine manually, if the unit is working properly. Yes I'm sure about the salt test. I did it twice to be sure.
    75'X12' 2-lane IG lap pool built in 2008. 33,000 gallons. Gunite construction with vinyl liner. All equipment is Hayward - cartridge filtration system, Mineral Springs SWG (not currently working - switched to adding chlorine manually), 300,000BTU natural gas pool heater. Also use a 4-panel solar system in summer. Pool is located inside a 25'X100' concrete block building w/natural gas forced air furnace/SIPS roof.

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    Re: How do you test a SWC to see if it's working properly?

    Based on the readings, it appears to be working correctly. How many hours per day does the pump run?

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    JoyfulNoise's Avatar
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    How do you test a SWC to see if it's working properly?

    The problem you are describing, i.e., FC dropping to 0 with the SWG running, is typically an algae bloom problem. SWG's can maintain a chlorine level but once an algae bloom gets started, no SWG can keep up with it. It requires manual chlorination at shock levels for extended periods of time to eradicate the algae problem. You need to SLAM your pool.

    Given that you have reported algae and that this is actually a high bather load, lap pool (presumably for some kind of swim school or swim team), your pool likely has an algae problem. You could confirm it with an overnight chlorine loss test (OCLT) but I will almost guarantee the pool will fail an OCLT.
    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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    Re: How do you test a SWC to see if it's working properly?

    If you see bubbles coming out of a return, get a barbecue lighter and wave it over them. You should hear a "crackles & pops" as you ignite the hydrogen produced as a byproduct.

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