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Thread: TA and CH readings are very low...should I adjust?

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    TA and CH readings are very low...should I adjust?

    Hi,

    I have not checked readings since November. We're just at the point here in PA where the water is starting to freeze over on the surface. Last year, with the new plaster, I was worried about scale and so several times had to lower the pH. Now, however, I seem to be looking at the opposite problem and am concerned about etching. I'm getting an SI of -0.9 due to the following readings

    pH - 7.6
    TA - 60 (can this be right?)
    CH - 100 (can THIS be right?)
    TEMP - 42

    I took the sample right from the skimmer bowl - which is not always entirely accurate but generally close. Also, the pool water level is up over the tiles and so I am theoretically sampling 'pool' water and not just accumulated rain water in the bowl. How could I have gone from CH of 190 back in November to 100? And how from a TA of 95 back in November to 60? I almost have to pull back the cover part way and get a sample from the pool, but might not be able to if there is too much ice.

    Should I be concerned, or just leave it as is? I don't think I can adjust the CH with the water being this cold anyway (?)

    Thanks,
    Keith
    12,000 gal. Anthony IG pool; 3 ft. shallow end to 6 ft. deep end; Built 1989; Renovated July 2014 using a 10-part unexposed quartz plaster aggregate of 3 S-grade Blue, 3 S-grade Gray, 2 T-grade Blue, 2 T-grade Gray; Apollo VA-52 DE Filter; Hayward SP-2607X10 Super Pump 1-HP Single Speed; Jandy AE-Ti Heat Pump; Taylor K-2006 Test Kit

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    Re: TA and CH readings are very low...should I adjust?

    I understand the issue of getting a good sample, but I don't like the sample from the skimmer at all......I do not think it is representative of your pool water.

    My first thought would be to figure a way to get a good sample of your pool water and compare.
    Dave S.
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    borjis's Avatar
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    Re: TA and CH readings are very low...should I adjust?

    agreed. I would wait for a thaw and run the pump a couple hours then sample from the deep end.

    My TA is down from 70 to 50 due to rain fills and draining down to skimmer level.
    16x32 IG Vinyl, 13,000 Gals. Hayward S-244T sand filter, SP2810X15 pump
    (1.5 HP motor) Raypak PR266AEN (266k btu) gas heater. TF-100 Test Kit.
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    Re: TA and CH readings are very low...should I adjust?

    Quote Originally Posted by borjis View Post
    agreed. I would wait for a thaw and run the pump a couple hours then sample from the deep end.

    My TA is down from 70 to 50 due to rain fills and draining down to skimmer level.

    I would not plan on running the pump being that the entire system is drained and antifreeze in the lines. I just use a kayak paddle (lol) and agitate the water for several minutes...probably still not a great sample but good enough I suppose.

    - - - Updated - - -

    Quote Originally Posted by duraleigh View Post
    I understand the issue of getting a good sample, but I don't like the sample from the skimmer at all......I do not think it is representative of your pool water.

    My first thought would be to figure a way to get a good sample of your pool water and compare.
    Yeah...I'm not content with the skimmer sample. I'm thinking that the CH reading I'm getting is probably mostly from rainwater and ice melt - since there was a decent amount of ice in there when I took the sample.
    12,000 gal. Anthony IG pool; 3 ft. shallow end to 6 ft. deep end; Built 1989; Renovated July 2014 using a 10-part unexposed quartz plaster aggregate of 3 S-grade Blue, 3 S-grade Gray, 2 T-grade Blue, 2 T-grade Gray; Apollo VA-52 DE Filter; Hayward SP-2607X10 Super Pump 1-HP Single Speed; Jandy AE-Ti Heat Pump; Taylor K-2006 Test Kit

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    Mod Squad zea3's Avatar
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    Re: TA and CH readings are very low...should I adjust?

    You can use a length of flexible tubing to slip under the cover and siphon a sample from 2-3 feet deep in the pool, however if you closed with a CH of 190 you were already too low. Minimum CH for a plaster pool is 250. It would be difficult to add CH while the pool is winterized since the added calcium may not dissolve well in the cold water.

    Most likely you are correct that the skimmer sample is rainwater and not representative of the bulk of the pool water. You can try and siphon out a better sample to test, but if the calcium is low it will be difficult to correct without opening the pool.
    TFP Moderator
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    Re: TA and CH readings are very low...should I adjust?

    I took off part of the cover - as I usually do when checking the water and adding any chemicals during the off-season. It turned out I was way off. The true readings are:

    pH - 8+ (guessing around 8.2 or 8.3)
    TA - 130
    CH - 230

    So I'm a bit in the scaling zone...added some pH decreaser, agitated the water around for several minutes, and then reattached the cover. That should do it probably until I reopen in spring. I might recheck in a few weeks unless the pool is frozen by then. Thanks to all who replied. I have to remember not to rely on water samples from the skimmer any more.
    12,000 gal. Anthony IG pool; 3 ft. shallow end to 6 ft. deep end; Built 1989; Renovated July 2014 using a 10-part unexposed quartz plaster aggregate of 3 S-grade Blue, 3 S-grade Gray, 2 T-grade Blue, 2 T-grade Gray; Apollo VA-52 DE Filter; Hayward SP-2607X10 Super Pump 1-HP Single Speed; Jandy AE-Ti Heat Pump; Taylor K-2006 Test Kit

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    borjis's Avatar
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    Re: TA and CH readings are very low...should I adjust?

    You hadn't mentioned you were at winterized levels in the first post so, yes my idea would not work.
    16x32 IG Vinyl, 13,000 Gals. Hayward S-244T sand filter, SP2810X15 pump
    (1.5 HP motor) Raypak PR266AEN (266k btu) gas heater. TF-100 Test Kit.
    Dolphin E10 Cleaning Robot.

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