WaterSpin vs. Taylor Test Kit

[scott.lopez]

Before I ask my question, I realize that a lot of people are in favor of the Taylor (and other) test kits. Given that I'm color blind and was struggling to identify if pH was in range or not I went ahead and ordered the water spin.

All measurements seem very accurate when comparing to the test kit (my wife verifying the colors). However, pH seems to be different. In an effort to verify the accuracy of the WaterSpin I used a disk, put in 6.9 pH calibration solution that the labs use and it was right on the money, there number was 6.89 and the WaterSpin was 6.9 (only one decimal place is shown in the LaMotte software).

First, is the use of a calibration solution at 6.9 pH a way to verify accuracy of a device? The taylor test kit doesn't go that low, it stops at 7 and goes to 8.

Would it be reasonable that the pH shown on the WaterSpin is accurate at 7.8 when analyzing the pool water even though the taylor test kit is showing 7.6? I'm not familiar enough with the taylor kit to know it's percent accuracy.



I don't want to put to much acid in the pool and I'm trying to keep the pH between 7.4 and 7.8.

Thanks

 

[Richard320]

Where'd you get the 6.9 pH solution? Maybe they make it in other pHs?

A quick google has found some 7 and some 10 standards.

 

[scott.lopez]

Thanks for the reply.

I ordered the packets from Amazon. I think they are typically used in lab analysis.

I did consider the different packets but the only options are 4, 7, and 9 (or 10). Unfortunately WaterLink stops reporting at 8.6, just shows 8.6 (OVR). I reduced the pH by mixing the 9.18 with the 6.89. Quickly remembered my great love for chemistry, switched to electrical engineering after two chemistry classes. Never the less, I switched to a different approach, used two different test strips to verify that the pH was 8.4 which matched the WaterSpin exactly (LaMotte test strips and Hach test strips). I'm assuming that since the water was rather pure (distilled water with the packets) that the test strips were accurate. That leads me to believe that the Taylor test kit is good but has some play in it, not unreasonable given the range of pH that is normally used (7.4 to 7.8). The WaterSpin seems to be very accurate and I wanted to be sure that when it tells me to add 6 cups of acid that I'm not going to create issues for myself with to much acid in the pool.

Do you see any flaws in my analysis?

 

[Richard320]

Thanks for the reply.

I ordered the packets from Amazon. I think they are typically used in lab analysis.

I did consider the different packets but the only options are 4, 7, and 9 (or 10). Unfortunately WaterLink stops reporting at 8.6, just shows 8.6 (OVR). I reduced the pH by mixing the 9.18 with the 6.89. Quickly remembered my great love for chemistry, switched to electrical engineering after two chemistry classes. Never the less, I switched to a different approach, used two different test strips to verify that the pH was 8.4 which matched the WaterSpin exactly (LaMotte test strips and Hach test strips). I'm assuming that since the water was rather pure (distilled water with the packets) that the test strips were accurate. That leads me to believe that the Taylor test kit is good but has some play in it, not unreasonable given the range of pH that is normally used (7.4 to 7.8). The WaterSpin seems to be very accurate and I wanted to be sure that when it tells me to add 6 cups of acid that I'm not going to create issues for myself with to much acid in the pool.

Do you see any flaws in my analysis?

Nope.

Now you just need to worry that you calculated the pool volume correctly. Knowing the pH to the second decimal point won't do you any good if the pool is 10% smaller than you think. Although you do have some wiggle room; it;s not a big deal if the pH drops to 7.2 instead of 7.4. It's still swimmable.

Have you seen Effects of Adding Chemicals in poolmath? It's a good way to doublecheck that you're getting the results you should be getting.

 

[scott.lopez]

I have seen the pool math calculator, great work by whoever created it. I've been verifying the suggestions of the WaterSpin against the pool math. Pretty close.

Good point on the pool volume, I did the calculations but it's probably a good idea to verify it again.

Thanks