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Thread: High FC after starting SWG and adding CYA

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    Join Date
    Jun 2016
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    Augusta, GA
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    High FC after starting SWG and adding CYA

    I think I know the answer to this but just need confirmation. Been posting and learning for about a month now and have found TFP methods intuitive and better than pool store advice.

    New house, new pool 1 mo ago. SWG cell old, not working. Pool not balanced, followed tfp recommendations. Got pool slammed, balanced for non-SWG. Got to know pool chemistry, maintained pool with bleach for a few weeks. Friday of last week, upped CYA from 30 in preparation for SWG cell replacement, aiming for 60. Got it to 53, but immediately after, could not maintain FC. Dumped a ton of bleach, got it back up to appropriate FC level of 6. FC dropped again overnight (day 2 of upping CYA), put in 2 more 121oz bleach bottles. That same day, I started adding salt to get it from 900 to 3000ppm. Then replaced T-15 cell. Got the cell working, let it run at 70% for a few hours to see how it did.

    Q1-- did the addition of CYA cause the FC to drop because it was binding with available FC? Or did something happen in my pool that I need to figure out?

    Q2--now my FC is at 16, my CYA is at 50, and FC seems to be maintaining (FC was 15 at 8:30am, 16 at 8:30pm, no bleach added, SWG ran for 70% for 4 hours)... all other values are good-- TA 80, pH 7.5. If I turn off the SWG for a day or two, I'm not sure with this higher CYA how long the FC will take to disappear. So, is it okay to let the pool just sit there with the SWG and pump/filter off? Or, should I re-set the schedule for the SWG to not be on, let the filter/pump run without it, and just keep rechecking FC?

    Q3--Lastly, is it safe to swim with these high FC levels? I know that the CYA is a buffer, but it seems a bit too high...
    21,000 IG vinyl, Goldline AQ-LOGIC-P4, 2017 Pentair Sand Dollar Top Mount Sand Filter, Flotec AT251001-01, Hayward T-15 Turbo cell
    Augusta, GA

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    TFP Guide

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    Re: High FC after starting SWG and adding CYA

    I suspect you lost so much FC because the new CYA was not fully available to protect that first big dose of chlorine, now it is so it is holding.

    For your CYA level you are safe to swim up to 20ppm I would not stop the pump just turn the SWG % down or off for a day or two the levels will drift down soon enough.

    Edit: Just rereading you said FC dropped over night I don't have a good explanation for that. I though you were saying it was not holding at the new higher level initially not depleting overnight
    12,300 Gallon, IG PebbleFina, 3 ft sheer, 2 Jandy nicheless LED lights, Jandy Pro 1.5HP VS pump (A.O. Smith Motor), PB4-60 Booster pump, Polaris 280, Jandy cv340 cartridge filter, Zodiac Z4 control panel W/iAquaLink, Stenner pumps for chlorine & MA connected to WiOn WiFi switches, TF-100. You can support TFP with AmazonSmile just click the link!

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    Re: High FC after starting SWG and adding CYA

    Yes, we had large FC loss both during day and overnight after adding CYA, which was odd. Our overnight FC never was a problem after slam, so why would it suddenly have changed? Thats why I wondered if CYA was making FC unavailable as it became mixed in....or if it signals a problem. We also added salt right after all the CYA dissolved...

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    Re: High FC after starting SWG and adding CYA

    Update today at 7am the FC was 13 (6pm last night, sun still up wasnt planning on doing overnight, FC was at 16).

    So, should I set the cell to run at something really low like 20% for an hour?

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    TFP Guide

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    Re: High FC after starting SWG and adding CYA

    I would set it low for a while till the FC gets to around 9 or 10 then do an OCLT just to be sure there is nothing in the water that needs to be dealt with. Having it just below 10 will allow you to get an accurate pH reading so if you do have to do a short SLAM you can be comfortable that other levels are as they should be. If you have some time can you please update your signature with info about your pool it can help others make informed suggestions. Directions on how to do that HERE
    12,300 Gallon, IG PebbleFina, 3 ft sheer, 2 Jandy nicheless LED lights, Jandy Pro 1.5HP VS pump (A.O. Smith Motor), PB4-60 Booster pump, Polaris 280, Jandy cv340 cartridge filter, Zodiac Z4 control panel W/iAquaLink, Stenner pumps for chlorine & MA connected to WiOn WiFi switches, TF-100. You can support TFP with AmazonSmile just click the link!

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    Re: High FC after starting SWG and adding CYA

    Ok, thank you, I had it back to 20% during the day from 11-4 on 7/7 and before bed it was FC 10, CC 0 pH 7.5 TA 85. Friday 7/8 at 6:30am it was FC 10, CC 0, and I let the SWG run from 7-4 at 20%. The FC at 7:30pm as of 7/8 was 7.5. I think things are good since no overnight loss yesterday?

    Should I try to increase the CYA again-- since it is at 50 and it should probably be around 70? I just don't know what caused the FC loss suddenly and don't want to mess with the CYA too much since that precipitated the FC loss... Is there any issue with a SWG running with a CYA of 50?

    I guess I'll up the SWG to maybe 40% to keep the FC at the high end of the range --3-9. The water is looking a bit cloudy, but we've had terrible storms here. Perhaps I can add some borates... and try to get those up to about 40. I have the test for that, since that was part of the plan after getting the SWG going.


    Sorry about the signature, it has been there, but the last post I did from my phone not computer??? not sure why, hopefully this post has the signature with all the info..
    21,000 IG vinyl, Goldline AQ-LOGIC-P4, 2017 Pentair Sand Dollar Top Mount Sand Filter, Flotec AT251001-01, Hayward T-15 Turbo cell
    Augusta, GA

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