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Thread: CYA measures <20 on my TF-100 test kit.

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    CYA measures <20 on my TF-100 test kit.

    I just took over maintenance of my parents 20 x 40 in ground pool. It was essentially a swamp when I started last week but is getting better each day. My father had always added chlorine with stabilized "pucks" so when I started I expected to see his CYA level about 100 or higher. I was shocked to see it did not even register any CYA. I filled the sight tube to the top of the tube with test solution and the black dot is still perfectly clear. I've checked it twice with the same result. I'm adding about four gallons of 8.25% bleach daily only to find the FC down to about 1.0 to 1.5 ppm the next day. I initially added two Trichlor pucks in each of the two skimmers then two days ago increased it to six in each but the CYA level has not yet increased. I'm thinking I need to add some CYA to get the level up to at least 20 to 30, then continue to use the Trichlor pucks and monitor the CYA level until it reaches about 45 before switching to chlorine bleach.

    Am I doing the right thing by adding CYA. The local pool store has it in solid form and is suggesting adding an eleven pound bag. Any advise on how to go about adding it. I did see these instructions on this site.... "Solid stabilizer can take up to a week to fully register on the test, so don't retest your CYA level for a week after adding some. Solid stabilizer is best added by placing it in a sock in the skimmer basket. The pump should be run for 24 hours after adding solid stabilizer and you should avoid backwashing/cleaning the filter for a week."

    Also the other test readings were way out as well. The TA was at 10 so today I added all the baking soda I had on hand. I added four 4 lb boxes which raised the TA to 40. I'll get some more for tomorrow. The pool has a vinyl liner so I want to get the TA up to 100 - 120. The PH is at 6.0 so I'll be adding borax but I think I remember reading not to do add borax and baking soda at the same time, so I'll do that later. The CH is at 200 but I'm not concerned with that. Like I said the pool has come a long way to recovery but I'm a little nervous about adding too much CYA and then have to do water replacement. Any advise would be appreciated. I should also note that the pool is an older pool (1975) and uses a Hayward sand filter.

    Dave.
    Dave
    18x36 ~25k gal, IG vinyl, Hayward Super pump VS (IS2600VSP), Hayward sand filter S244T, Hayward CL200 auto chlorine feeder, Zodiac G3 cleaner, Pool install July 2014, TF-100 test kit.

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    Georgia
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    Re: CYA measures <20 on my TF-100 test kit.

    If you think your cya is less than 20, just be on the safe side and say its 20 ppm and add 20 ppm of solid stabilzer then wait a week and retest. It should show up better with the test at that point then you can add more if needed. That way you would be somewhere between 20 and 40 ppm CYA. I put mine in a pair of pantyhose legs hanging in front of the return. It will dissolve in about a day or day and a half. That way I dont have to run the pump for 24 hours.

    Try a TA of 70-80 ppm and see if your pH is stable. There is probably no reason to go to 100 ppm unless your using something acidic like Trichlor.

    If your pH is 6.0 you probably dont want to wait until later to adjust it. That needs to be done first.
    16k AG Vinyl Sand Filter

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    Re: CYA measures <20 on my TF-100 test kit.

    After adding the four boxes of baking soda yesterday to raise the TA, I found the PH was up also to about 6.8. Since that's still too low I added three boxes of borax (20 mule team 76oz) and measured ph again. The ph reading was about 7.0, so I went to the store for more borax and added two more boxes. Checked the ph again and found it was 8.0 to 8.1. Looks like I overshot my goal on ph. I'm sure I didn't wait long enough to take the first reading after adding the three boxes of borax. I don't really have enough time to work on the pool on my work days (12 hour shifts) so I rushed the process and went too far adding borax. Now I'll probably need to add some muriatic acid but I think I'll wait to see if things settle out. I didn't have time to check the TA level today but I'll get that tomorrow.

    I also want to add some CYA tomorrow but I think I'll start with about four pounds. Definitely don't want to overshoot with CYA. Also the CYA instruction quote above said not to backwash for a week after adding CYA. I can see this is going to be a problem. Today the PSI on the sand filter was 45 PSI way up from a norm of 32 PSI. After backwashing the PSI was back to 32. If it goes that high again I will have to backwash.

    I have two questions. Is the 8.1 ph reading something that needs to be addressed right away? If the sand filter pressure builds up to about 45 PSI again is it more important to backwash even though CYA has been added and backwashing is not recommended?


    Dave.
    Dave
    18x36 ~25k gal, IG vinyl, Hayward Super pump VS (IS2600VSP), Hayward sand filter S244T, Hayward CL200 auto chlorine feeder, Zodiac G3 cleaner, Pool install July 2014, TF-100 test kit.

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    Richard320's Avatar
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    Re: CYA measures <20 on my TF-100 test kit.

    If you put the CYA granules into a sock the way we suggest and don't just pour the stuff down the skimmer so it settles in the filter, you can backwash without losing hardly any CYA. But if you follow the bottle label, the granules will settle in the filter and the first time you backwash, anything that hasn't dissolved will be gone. Money down the drain.

    The CYA will lower pH a little bit, but I'd say you need to lower pH with Muriatic Acid to 7.6 or so ASAP. High pH can lead to Calcium Scale formation.

    You need to slow down a little when you add things. Overshooting wastes chemicals, and then you need to add more chemicals to fix it and you might as well get back on the pool store merry-go-round - up and down and round and round and never get anywhere.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: CYA measures <20 on my TF-100 test kit.

    Agree completely with the advise to slow down. Not the way I normally do things. I'll make it a priority to add Muriatic Acid tomorrow and shoot for a ph level of 7.6.

    Thanks,
    Dave.
    Dave
    18x36 ~25k gal, IG vinyl, Hayward Super pump VS (IS2600VSP), Hayward sand filter S244T, Hayward CL200 auto chlorine feeder, Zodiac G3 cleaner, Pool install July 2014, TF-100 test kit.

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    Mod Squad pooldv's Avatar
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    Re: CYA measures <20 on my TF-100 test kit.

    Are you using Pool School - PoolMath to calculate how much stuff to add? Here is some more info on Pool School - Recommended Pool Chemicals
    TFP Moderator
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    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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    Re: CYA measures <20 on my TF-100 test kit.

    +1 on pooldv's suggestion to use PoolMath. I could never maintain a pool without it.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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