How to run the CH test

[Terry]

I thought I read a post once referring to a 'How To' article written by Waterbear on how to run the CH test. I'm ready to run my first CH test and want to make sure I'm doing it right, but can't find the article via a search. If this actually exists, can someone point me in the right direction?

Thanks!

 

[Guest]

add the first reagent, swirl for 20-30 seconds. add the indicator (second reagent) and swirl to mix well. add the titrant one drop at a time and swirl for 20-30 seconds between drops.

If you get a purple endpoint or 'floaties' in the sample add 6 drops of reagent 3 (the titrant) FIRST and swirl to mix then proceed with the procedure above. Be sure to include the first 6 drops you added in the final count of drops.

 

[waste]

You the bomb!!! :fro: Thanx Evan - I so rarely test ch in liner pools I'd forgotten that

 

[Terry]

Thanks! I wanted to make sure I did it correctly, unlike the CYA test where I discovered after a month of testing that I was supposed to be holding it at waist level and performing the test in direct sun.

 

[Guest]

Thanks! I wanted to make sure I did it correctly, unlike the CYA test where I discovered after a month of testing that I was supposed to be holding it at waist level and performing the test in direct sun.

I do the CYA test in open shade.

 

[billybrobob]

waterbear -

If you have a magnetic stirrer, does the 20 sec swirl time apply between drops in the CH test? i.e.- Is this about good mixing or is it a time to chemically react issue. CYA test included in this question.

Also, for example, if you know your CH is btween 300-400 ppm, can you add 29 drops before you slow down? This applies to all tests.

 

[Guest]

waterbear -

If you have a magnetic stirrer, does the 20 sec swirl time apply between drops in the CH test? i.e.- Is this about good mixing or is it a time to chemically react issue. CYA test included in this question.
It's about good mixing so the reagent can react. A magnetic stirrer speeds up this test considerably!
Also, for example, if you know your CH is btween 300-400 ppm, can you add 29 drops before you slow down?
I would not recommend it. It's a sure way to get 'floaties' that make the endpoint difficult to read.
This applies to all tests.

 

[Terry]

Ok, ran the test, twice. First test, initial color pink- and a light pink at that. 16 drops turned the sample very light blue (or maybe light purple?). Continued on 3 more drops with no noticeable change in color. Decided to do a second test as maybe my end point was purple. Started w/ the 3 drops, didn't swirl btwn them and think maybe I got floaties? Don't really know what floaties are, but could see floating dots of a darker pink color- lots of them. Anyway, initial color was the same light pink, and 16 drops later color turned to the same light blue/purple. Continued this test on to 20 drops with no change in color. So, do you think I did it right? What is the implication of a purple end point?

 

[billybrobob]

Thanks for your advice. Have been wondering about that. As an aside, I read your bio in the newsletter. I know you aren't looking for accolades in your other life, but it is noted and appreciated.

 

[frankgh]

I just picked up a Taylor K-2005 test kit. It is reading CH about 200ppm higher than my local trustworthy pool store. Any idea what would cause that?

 

[JasonLion]

Pool stores getting wrong results is very common. The CH test takes time, and pool stores often don't want to spend that much time. If you rush the test you get inaccurate results.

 

[CaOCl2]

Pool stores getting wrong results is very common. The CH test takes time, and pool stores often don't want to spend that much time. If you rush the test you get inaccurate results.

A bit like another forum participant, earlier this year I took the same water sample to six pool stores and observed how they tested the water. Lots of things to say but specifically for the CH test, the results were: 180, 210, 170, 145, 180 and 210 ppm (the correct value being 180).

You can get standardized solutions of calcium hardness (as well as CYA, alkalinity and pH) from Taylor. You test 25 mL as you would a water sample. They allow you to confirm that your reagents are ok and that you're doing the test right.

Perhaps Duraleigh can make them available (in smaller sizes than the standard 473 mL).

 

[Guest]

You can get standardized solutions of calcium hardness (as well as CYA, alkalinity and pH) from Taylor. You test 25 mL as you would a water sample. They allow you to confirm that your reagents are ok and that you're doing the test right.

Perhaps Duraleigh can make them available (in smaller sizes than the standard 473 mL).

THAT is a GREAT idea!
Dave, are you listening?

 

[TomU]

You can get standardized solutions of calcium hardness (as well as CYA, alkalinity and pH) from Taylor.

I was having trouble finding these on their website. I called and here are the part numbers if anyone is interested:

• R-7062-E Buffer Solution pH - 7.6 (16oz)[/*:m:fgn99ffj]
• R-7063-E Hardness Standard - 200ppm (16oz)[/*:m:fgn99ffj]
• R-7064-E Alkalinity Standard - 100 ppm (16oz)[/*:m:fgn99ffj]
• R-7065-E CYA Standard - 50 ppm (16oz)[/*:m:fgn99ffj]
• K-7066-E 4-Pack (includes all of the above items)[/*:m:fgn99ffj]

They also sell the above solutions in gallon sizes. I would think that would make it fairly easy for Dave to resell, should he decide to do so. Does anyone know if any of these would have a short shelf life?

 

[Guest]

There is nothing in them to go bad except if they are left open and evaporate, changing the concentration.