Does A low CH have any effect on measuring TA

smeestu · Sep 20, 2015

I have another question for you all i have been testing the T/A and CYA and CH once a month which seems to be fine they are pretty steady untill the last 6/8 weeks we have had some really heavy rain upto 10cm in one go.so ive had a fair bit of run off had to open the overflow several times . Anyways ive brought the CYA back up but the CH has dropped down to 150 from 260 would this have any effect on measuring T/A as i am not getting the clear colour change i used to get it goes to a dark pink colour and not the obvious red it used to the tablets have been kept dry and out of sunlight .Could the CH dropping down that much have any effect on the TA test
i use Palintest kit.The PH is rock solid it dropped a bit as i used some spare trichlor to bring the CYA back up to 75 the ph moved from 7.7 to 7.5 over 2 weeks and now its been there for 2 weeks without moving at all i dont have any PH drift problems the pool is crystal clear i have not had any algae cloudy water prolem since is started using the method here about 12 months ago.I might have to raise the CH with CAL-HYPO slowly over time as chemicals here where i live are not easy to get hold of.

"palintest Total Alkalinity Test Tablets in a 250 tablet bottle - Total Alkalinity in a range of 0 - 500mg/l
Total Alkalinity - 250 Tablets - Add one tablet to sample in a stoppered container. Shake to disintegrate tablet. Repeat until yellow colour changes to bright red.
Total Alkalinity can then be calculated as:
50ml sample container = number of tablets added multiplied by 40 then minus 20 to give you your Total Alkalinity reading. i.e. 6 tablets added, so (6 x 40) - 20 = 220 mg/l
100ml sample container = number of tablets added multiplied by 20 then minus 10 to give you your Total Alkalinity reading. i.e. 11 tablets added, so (11 x 20) - 10 = 210 mg/l "

FC 6.0
CC 6.0
CYA 75
CH 150
TA goes dark pink at 70 and does not change even upto 10 tablets ( on 50ml sample)

Texas Splash · Sep 20, 2015

smeestu, I'm not aware of CH impacting TA testing. Even though you stated it dropped from 260 to 150, that should have no bearing on TA. I suspect the huge drop was from all the rain you received. I'm not familiar with the Palintest Kit, but if your numbers above are accurate, I would be concerned with the high CC (Combined Chlorine) number.... unless you meant to say Total Chlorine.

Maybe some other members will have some experience with your particular kit.

smeestu · Sep 20, 2015

Texas Splash said:
smeestu, I'm not aware of CH impacting TA testing. Even though you stated it dropped from 260 to 150, that should have no bearing on TA. I suspect the huge drop was from all the rain you received. I'm not familiar with the Palintest Kit, but if your numbers above are accurate, I would be concerned with the high CC (Combined Chlorine) number.... unless you meant to say Total Chlorine. Maybe some other members will have some experience with your particular kit.

Thanks for the reply yes i meant total chlorine the numbers are accurate i tested the CH and the TA twice once with a 50ml sample (resultion of 40) then with a 100ml sample and the answers came out the same . I just cant understand why the sudden loss of colour change the test kit is very clear normally one extra tablet and it changes colour 100% very easy to read up to now maybe ill try dropping the FC down a bit see if that makes any difference looking back over my notes it was around 3.0 last few tests maybe its bleaching it out a bit .As for the drop in CH i agree must of been the heavy rain we had but i cant buy calcium chloride anywhere near me so im stuck will have to use Cal-Hypo and do it slowly maybe turn off the SWG for a few weeks and bring it up slowly with the Cal-Hypo though 10kg with pool math will take up my CH by 47 so its going to take some time .

Richard320 · Sep 20, 2015

It could well be the FC level. I know at high FC levels the Taylor kits shifts TA from green> pink to blue>yellow. The actual color is not as important as the distinct change.

smeestu · Sep 20, 2015

Richard320 said:
It could well be the FC level. I know at high FC levels the Taylor kits shifts TA from green> pink to blue>yellow. The actual color is not as important as the distinct change.

Thanks for your reply after thinking about it a bit more i did think that maybe the higher FC is "bleeching out" the colour change a bit will drop the FC down to 3.0 and test again all a learning curve and i know i use a test kit not many others use . Its due to what i can get here in Thailand but it seems pretty acurate and i havent had to slam or do anything too much since ive followed the giude lines on here so happy days

chem geek · Sep 21, 2015

You can add more thiosulfate drops to dechlorinate the water as part of the TA test. Taylor kits have that reagent and with high FC one can use more such drops.

smeestu · Sep 21, 2015

chem geek said:
You can add more thiosulfate drops to dechlorinate the water as part of the TA test. Taylor kits have that reagent and with high FC one can use more such drops.

Thanks for the input would diluting the sample 50% with distilled water so in effect making the FC 3.0 then doubling the TA result work. I am unable to get Taylor test kit here in Thailand.

chem geek · Sep 21, 2015

You could do that, but I'm very surprised that your test kit doesn't have a chlorine neutralizer as part of the TA test. Do you have access to hydrogen peroxide? If so, then you could use that to neutralize the chlorine in the sample. One drop (assuming 24 drops/ml) of 3% hydrogen peroxide in 2 cups of pool water would neutralize 5 ppm FC.