Question about CH testing with K-2006

[harrisjc]

I bought a K-2006 test kit yesterday. Here’s what I came up with:

FC 3.0
CC 0
PH 7.8
TA 70
CH 570 ? Maybe
CYA <30
Temp 76

I really question the CH test results. When I do the TA test it is very stark change from green to red. I expected the same definite results with the CH test. It is supposed to change from red to blue.

I put in the 20 drops of R-0010 and then the 5 drops of R-0011L. It is supposed to turn red if CH is present. It turns the solution a little bit red. And the red is grainy looking. I start adding R-0012 and it never really turns blue in a dramatic way. It turns more of a clear color then a barely detectable light, light, light blue.

First of all do you guy get a grainy solution after adding the 5 drops R-0011L?

Do you get a dramatic red to blue change when you do the CH test?

Another question mark is the K-2006 re-agent. When I bought it at another local pool store the guy told me that it was ordered and never picked up. I asked him how long the K-2006 had been sitting on the shelf. He said, “Oh, a couple of months.” After seeing the grainy solution, I question the re-agent freshness.

fyi … This is the first time that I’ve checked my CH. After browsing TFP I am guessing that CH has been low since the pool was built since I have white and some yellow Crud coming out of my grout – even 18 inches above the water line. I’m thinking that is dissolved calcium. Wish I had known about TFP back at the start.

 

[Richard320]

For real high CH, try this:

When high CH is anticipated, this procedure may be used: Use
10 mL sample, 10 drops R-0010, 3 drops R-0011L, and multiply
drops in Step 4 by 25.

That's straight from Taylor

You can also try adding 5 drops or so of R-0012 first, then use the regular procedure. Don't forget to include the first few drops in the count.

 

[frustratedpoolmom]

The CH test is a tricky one and will not be as obvious as the TA test was.

You are looking for any color change - the precise color doesn't have to be exact. The clear to light light blue is your end point.
You can read about performing the test here:http://www.taylortechnologies.com/ChemistryTopicsCM.ASP?ContentID=70

 

[257WbyMag]

For your purposes, it's probably best to go with the smaller sample (10 ml) since it saves you on reagent and 25 ppm accuracy is plenty fine.

Richard is right too. To deal with the fading endpoint issue, add 5 or 6 drops of the R-0012 first (including them in your drop count later) and then add the R-0010 and R-0011L as ordered.

Purple is not your endpoint. Blue is and as FPM said, it may be very, very light. This test doesn't produce sudden and dramatic color changes.

 

[JasonLion]

The reagents can last a long time if they are stored properly. They like constant temperatures and can be ruined by freezing, very high temperatures, or lots of direct sunlight. Kept in darkness at a constant room temperature they can last for years.

 

[harrisjc]

Thanks. Now I think I have a feel for it. After the advice above, I am calling it at 510 ppm.

 

[frustratedpoolmom]

With that high of a CH level - and your SWG - you are at risk for scale- be sure to keep your PH from kreeping above 7.8. I would try to hold it at 7.6 if you can.

 

[harrisjc]

Thanks. I already have scale. It is a constant battle to keep my pH down. It'll shoot up if I don't stay on top of it. Though it is a bit easier to control now. During the first couple of years with the pool I needed to add a quart of MA every couple of days. I am just beginning to track my pH level along with the amount of MA that I add.

 

[chem geek]

Unless your pool isn't exposed to sunlight, you should have your CYA level closer to 80 ppm with a corresponding FC minimum of 4 ppm as described in Water Balance for SWGs. The higher CYA level should reduce chlorine loss from sunlight and that should let you turn down the SWG on-time and that should reduce the rate of pH rise and amount of acid you need to add. You can also add 50 ppm Borates for further pH stability and possibly lower acid addition if you have some nascent algae growth in the pool (blown-in algae, etc.). You can also lower the TA even further in your case due to the high CH level in which case a pH target of 7.8 won't be bad. Your saturation index will be near zero if you have your current numbers except for a CYA of 80 ppm and keeping your TA at 70 ppm. You could lower it to 60 ppm and still be in good shape at a pH of 7.8.

 

[harrisjc]

Chem thanks. Good info.

I started playing around with the Pool Calculator - very cool.

When I got back on Sunday after being gone 6 days my pH was at 8.2 and CSI was 0.52 (pH was 7.6 when I left). Added 2 qts MA and today pH was 7.6 and CSI was at -0.01. I'm going to drive up my CYA as you suggest and test my Borate level then adjust - though my dogs do drink occasionally from the pool.

Wish I had been on this site when I first got my pool. I just thought scale - and before that dissolved calcium from grout - were just normal things that you had to clean and maintain.