Veryifying plans

[Raiken3712]

Just want to verify how much pH will lower with CYA. I'm probably going to start with 10 CYA to test how fast we lose it because I still have one verified leak we aren't quite ready to fix until fall/winter at the earliest.

If it doesn't lose too much after a week we'll probably up the number up to the recommended 30. The pH is currently 7.6 with a TA of 80 and CH of 380 with TDS at 800..Total dissolved solids..not sure what that entails exactly, but I listed since its on the pool test I got from Leslies.

I know from prior reading that TA and pH are related in regards to acid changing pH...or at least thats the impression I got, but I'm not completely sure how much change to expect.

Thanks for any input on what I should do. pH is just about perfect where it is so if getting it to 10 and than 30 won't effect it that much I guess I can go ahead and leave not mess with the pH after adding the CYA. Considering the pH of the fill water when last tested was 8.0 it will likely trend up over time when we have to readd due to water evaporation...but the rate of loss is certainly less than before we fixed 2 other leaks so that'll probably be at least a month.

 

[linen]

The addition of cya does not move ph much. You can use the "effects of adding chemical section of the poolcalcultor.com to find out how much. For your pool, adding 88 ounces of cya to raise cya 30 ppm should lower your ph ~ 0.6 Are you certain you have not used any chemicals that have added cya to your pool?

You really need to get an appropriate test kit since pool store results are unreliable (and often wrong on cya) and not available when you need them. See: http://www.troublefreepool.com/pool-school/pool_test_kit_comparison

Ignore TDS, it is not a useful measurement.

 

[duraleigh]

I'm probably going to start with 10 CYA to test how fast we lose it

That won't work for you.

You can certainly add a dosage of CYA to get to 10 ppm but you cannot test for it. The lowest measurable test value for CYA is 20 ppm.

 

[Raiken3712]

Good to know I guess I have to do 20 just for a test than..wish the tests were more precise. I thought the kits you could buy were similar to the ones the pool stores use? One of the kit is a Leslies kit I thought..

 

[linen]

Occasionally some leslies carry the taylor K-2005, but that does not have the most important FAS-DPD chlorine test (not to be confused with the DPD chlorine test). Only the Taylor K-2006 and the tf-100 have that test. It is rare/unlikely that any leslies will carry the K-2006 locally. Many of us have gotten the tf-100 since that is the best value

 

[Donldson]

Good to know I guess I have to do 20 just for a test than..wish the tests were more precise. I thought the kits you could buy were similar to the ones the pool stores use?

Despite what the pool store would have you believe, their testing is as accurate or less accurate than the ones we use. They may give you a sheet showing a CYA of 10, or 12, 157, but it is only to make people believe their testing is better than what can be done at home. CYA can only be accurately measured between 20-100. To add to my rant, when they say your FC is 2.39 (for example), it is also fake. Unless they are using the FAS-DPD test and using a 500 ml sample they can not test to a 0.01 ppm precision. It doesn't matter if their super wiz-bang computer has lasers attached to it's tester, they are not as precise as they like to pretend they are.

EDIT: I meant to say CYA can be measured between 20-100 in increments of 10. That is as accurate of any reasonably priced CYA test I know. Since most pools should be between 30-80 this is an acceptable range.

 

[Raiken3712]

Well they use a test kit that looks much like the FAS-DPD...of course I don't know what kind it is so it might not be as good. CYA can't be measured more precisely? 30-100? That means the measurement for it isn't even precise with a good kit. Hmm

I'm not sure what size the bottles used for the samples are so I have no clue of their sample size...its a small bottle. I'd say maybe a pint but don't know. 4 pints to a quart 4 quarts to a gallon...that could be about right.

 

[techguy]

Are they using a powder to run the FC testing? Or just drops?

 

[linen]

The cya test that comes with the tf-100 can measure down to 20 ppm. I think the taylor K-2006 only measures down to 30 ppm.

The FAS-DPD test is a "count drops until the solution turns clear" method.

 

[Donldson]

I'm not sure what size the bottles used for the samples are so I have no clue of their sample size...its a small bottle. I'd say maybe a pint but don't know. 4 pints to a quart 4 quarts to a gallon...that could be about right.

I'm sorry, I didn't make it clear I was joking. To get a 0.01 ppm FC precision with an FAS-DPD test they would need half a liter of water, a teaspoon or two of powder, and several hundred drops of reagent. All of this would cost several dollars per test and give completely useless precision. Rarely do you need more than 0.5 ppm precision. Very rarely you could use the 0.2 ppm precision. You would never need 0.01 ppm precision.

Anyway I doubt they are using an FAS-DPD test, most likely a DPD "match the shade of pink" test, which isn't much more useful than the yellow block test in a cheap test kit. But either way I can guarantee they are not doing a test that is actually capable of measuring to 0.01 ppm FC.