Water Test and Discrepancies.

[BTERRY1]

Here is a little background about my pool testing procedures. I test my water once a week. usually on Saturdays as I almost always need to add acid. On a monthly basis I break out my Taylor kit, but for quick checks mos weekends, I just use the Aquacheck 7 strips. This weekend cleaning the pool, I noticed the mottling of my dark plaster was worse than normal. I have posted here before about it, and will follow up with questions in that thread. What I found seems to be a large discrepancy between the Taylor kit and the strips when it comes to (CH). I will post my total results below and an image of the strip.

Taylor
FC 3.5
PH 7.7
CYA 50ish
CH 230ish (it takes me between 45 and 50 drops to get it from pink to purple to finally blue again.

Aquacheck - most values above matched except CH. please see attached image. to me it seems to be over 500 in the image. I find it kinda hard to believe with the 18" of rain in 7 weeks, and the amount of draining i have been having to do. had to add 40lbs of salt this weekend too.

 

[Donldson]

Well, to put it quite bluntly: test strips are junk. Period. They shouldn't be used ever. Throw them away.

To be honest, it sounds like your reliance on test strips and infrequent reliable testing has caused some damage to your pool finish.

 

[ajw22]

And your question you would like us to help you understand is?

 

[Randrx2]

CH 230ish (it takes me between 45 and 50 drops to get it from pink to purple to finally blue again.

If your drops are between 45-50, then wouldn’t your CH would be 450-500? I am assuming you are using a 25ml test sample. From the Taylor instructions: “Multiply drops in Step 4 by 10.”

 

[jseyfert3]

CH 230ish (it takes me between 45 and 50 drops to get it from pink to purple to finally blue again.

I believe a purple color indicates a problem with the test. Hopefully someone with more experience can chime in, but purple is noted here, along with what to do about it. Calcium Hardness - Trouble Free Pool

My own test for CH goes purple too. I've tried the 5 drops before starting trick and it still goes purple. I haven't gotten around to doing the 50/50 distilled water check yet, as CH isn't that important for my standalone plastic spa, but it is for you.

CH 230ish (it takes me between 45 and 50 drops to get it from pink to purple to finally blue again.

Wait, what? That math doesn't work out. The test is either 10 ppm per drop when using a 25 mL sample or 25 ppm per drop when using a 10 mL sample. Assuming no metal interference (see above portion of my post), If you used a 25 mL sample that would be a CH of 450-500 ppm. If you used a 10 mL sample that's a CH of ~1200 ppm.

 

[BTERRY1]

If your drops are between 45-50, then wouldn’t your CH would be 450-500? I am assuming you are using a 25ml test sample. From the Taylor instructions: “Multiply drops in Step 4 by 10.”

oops my bad. yes i am actually at 450 to 500.

Well, to put it quite bluntly: test strips are junk. Period. They shouldn't be used ever. Throw them away.

To be honest, it sounds like your reliance on test strips and infrequent reliable testing has caused some damage to your pool finish.

i regards to my infrequent reliable testing causing the damage, please enlighten me on this? I am trying to understand what would have caused this, and can i prevent it from getting any worse in the future? What water parameters would cause this? looking at my readings, it appears things are not terribly out of whack. what am I missing?

 

[ajw22]

My own test for CH goes purple too. I've tried the 5 drops before starting trick and it still goes purple. I haven't gotten around to doing the 50/50 distilled water check yet, as CH isn't that important for my standalone plastic spa, but it is for you.

Water Testing Errors - Further Reading

www.troublefreepool.com

Calcium Hardness Test Interference - interference from copper and iron can cause a fading endpoint and some color changes before the final endpoint.

General Test Interferences

 

[ajw22]

I am trying to understand what would have caused this, and can i prevent it from getting any worse in the future? What water parameters would cause this? looking at my readings, it appears things are not terribly out of whack. what am I missing?

Post an accurate full set of test results from your Taylor test kit not some ish numbers.

FC
CC
pH
TA
CH
CYA
Water Temp
CSI

For CYA is the dot disappears between 50 and 40 we round up and call it 50. We don't know if 50ish is 40, 50 or 60.

How do you get pH of 7.7?

 

[jseyfert3]

Water Testing Errors - Further Reading

www.troublefreepool.com

Calcium Hardness Test Interference - interference from copper and iron can cause a fading endpoint and some color changes before the final endpoint.

General Test Interferences

Yeah, it doesn't seem to actual fade at all. It just goes purple for a really long time. I'll have to watch Taylor's video, see if it has more information. I've read through Taylor's manual and the extended test kit directions here. My test results aren't orders of magnitude off from the city water quality report, but they do seem a little high, so I do think I have interference. Which is what I said. I plan to do the distilled water dilution test outlined in the extended test kit directions here and see if that helps once I refill my spa in a few days (down due to a broken pump drain plug hose adapter).

Anyhow, enough hijacking the OP's thread. I just mentioned it in case that was a testing issue the OP may be having.

 

[BTERRY1]

Post an accurate full set of test results from your Taylor test kit not some ish numbers.

FC
CC
pH
TA
CH
CYA
Water Temp
CSI

For CYA is the dot disappears between 50 and 40 we round up and call it 50. We don't know if 50ish is 40, 50 or 60.

How do you get pH of 7.7?

sorry for the delay. conference calls for work. here is what i get being as accurate a i can.

FC 4.5
CC 1 (this one barely turned pink after the 5 drops of R-003 and then only took 1 drop of R-0871 to get clear again
PH 7.6
TA 70
CH 450
CYA 55
Temp 66
CSI ?? - how do i get this?

thanks for everyones help.

 

[ajw22]

CSI ?? - how do i get this?

PoolMath or PoolMath

On the PoolMath app you need to turn on Tracking CSI in Options. Then log all your tests results and it will calculate CSI.

Calcium Saturation Index (CSI)

How is CSI calculated? Very simple – use our PoolMath tool. To ensure long plaster life and save money, click here to learn more.

www.troublefreepool.com

 

[jseyfert3]

CC 1 (this one barely turned pink after the 5 drops of R-003 and then only took 1 drop of R-0871 to get clear again

The FC test (including CC test) is either 0.2 or 0.5 ppm per drop, depending on sample size. So wouldn't that be a CC of 0.5 assuming you used a 10 mL sample size?

 

[BTERRY1]

PoolMath or PoolMath

On the PoolMath app you need to turn on Tracking CSI in Options. Then log all your tests results and it will calculate CSI.

Calcium Saturation Index (CSI)

How is CSI calculated? Very simple – use our PoolMath tool. To ensure long plaster life and save money, click here to learn more.

www.troublefreepool.com

-.027 is what pool math came up with. the only thing it is asking me to do is raise my CYA from 55 - 70

 

[aeh0603]

We always round CYA up to the nearest 10, so call your CYA 60. The scale is not linear, it's logarithmic so you can't guess between the lines.

 

[aeh0603]

Here is the update to your numbers:

FC 4.5
CC 0.5 (you use the same multiplier as the FC test, so for a 10ml sample, 1 drop is 0.5)
PH 7.6
TA 70
CH 450
CYA 60 (we round up)
Temp 66
CSI -0.28 (assuming 3500 salt, I got this by plugging your numbers into pool math. There is a link at the bottom of the page, or you can download the app)

Honestly, your numbers look pretty good to me. You will want to add a little more CYA as we get closer to summer, but there is not a huge rush this early in the season.
Test strips have a bad rap on this site since they are not known for accuracy. I would not do any chemical additions based on test strip results. If I were you, I would probably test with your taylor kit at least once a week or whenever you need to make chemical additions. If you want to use test strips as a quick check through through the week that's your decision, but doing a quick check of just FC and PH with your taysor kit is better. Test strips are known for being unreliable, so they are not recommended. The biggest risk you have with the test strip is that it tells you everything is in the acceptable range when it's actually not. If that happens you could have your water in a range that is damaging your pool or equipment, or not properly sanitized without you knowing.