Taylor calcium hardness test with spa vs pool strange results

[Maverick23]

I am having a strange issue when attempting to test CH in my spa.

When testing my vinyl pool which is currently about 75 degrees F I have no issues performing the CH test. Solid pink and blue color indications.

Now here is when it gets weird. I have added (too much calcium I believe) to the spa but when I go to run the test on the spa water I get little to no color change when adding the calcium indicator solution. I know there is a measurable amount of calcium is in the water based on what I added but the test does not indicate any calcium being present.

Other posts I saw said that the reagents might be bad but I know that is not true because I can run it on my pool water.

I am using Bromine in the spa and have the temp set to 101 F. Can temperature or bromine impact the effectiveness of this test? I don't know what else could cause it to respond differently.

PH 7.5
TA 50
CYA 0

I appreciate the input.

 

[Maverick23]

I tried to perform the test modified for interference with the same results. The sample is a very light pink with no color change even after 100 drops of reagent 12 added.

I notice that the pink color in the sample tube is actually in a precipitate form (small pink precipitates floating in the sample). This only happens with spa samples and not pool water.

 

[ALK753]

What's your sanitizer level (in your case bromine)?

 

[Maverick23]

What's your sanitizer level (in your case bromine)?

I am in the process of purging the tub and starting again. I ran some ahh-some cleaner through the tub and am going to start again. I will report my sanitizer level on the next round.

 

[HermanTX]

Now here is when it gets weird. I have added (too much calcium I believe) to the spa but when I go to run the test on the spa water I get little to no color change when adding the calcium indicator solution. I know there is a measurable amount of calcium is in the water based on what I added but the test does not indicate any calcium being present.

IS your spa a separate body of water from the vinyl pool? They do not connect or flow from 1 to the other?
What was the CH of the vinyl pool?
Have you tested your tap water? What is that Ch level? You can correlate it to your water district report of CH levels.

Good article from Taylor Technologies

Understanding Calcium Hardness

 

[Maverick23]

IS your spa a separate body of water from the vinyl pool? They do not connect or flow from 1 to the other?
What was the CH of the vinyl pool?
Have you tested your tap water? What is that Ch level? You can correlate it to your water district report of CH levels.

Good article from Taylor Technologies

Understanding Calcium Hardness

The spa is separate from the pool. I have the pool at 425PPM measured yesterday. Tap water is 75 PPM (3 drops with 10ml sample), county sample showed 64 PPM for calcium for August, no September report published yet.

The article is a good resource and I did read though that as well.

 

[HermanTX]

The spa is separate from the pool. I have the pool at 425PPM measured yesterday. Tap water is 75 PPM (3 drops with 10ml sample), county sample showed 64 PPM for calcium for August, no September report published yet.

The article is a good resource and I did read though that as well.

So your reagents appear good as matching to the county measurement (using a 10ml sample has 25ppm per drop - so higher than 50 and no more than 75)

If you put fresh water in hot tub then your test should measure about the 75ppm again.

Just curious, why is the pool so high in CH? Do you use cal-hypo for sanitation?

 

[mgtfp]

I'm wondering if that's an extreme case of a fading endpoint. Maybe try the distilled water dilution trick from the extended test directions:

Calcium Hardness

A drop-based test that measures the hardness in your water. Once measured, it is used … Read more…

www.troublefreepool.com

But seems that you are starting over again anyway and that will likely resolve the issue.

 

[JoyfulNoise]

Your hot tub water had too much calcium in it. You stated that was the case as you said you think you added too much. The test is telling you that is true because the water turned pink/red and never turned blue. The Taylor CH test is really only good up to about 800ppm CH. after that point, the indicator dye will have problems with high mineral levels. The short answer is - you simply added too much calcium to the water.

I suggest simply operating your tub with your current tap water and don’t bother increasing the CH. As long as you have about 50ppm or more of CH, you won’t get any foaming in the water. Adding additional calcium does nothing for the hot tub.

 

[Maverick23]

Your hot tub water had too much calcium in it. You stated that was the case as you said you think you added too much. The test is telling you that is true because the water turned pink/red and never turned blue. The Taylor CH test is really only good up to about 800ppm CH. after that point, the indicator dye will have problems with high mineral levels. The short answer is - you simply added too much calcium to the water.

I suggest simply operating your tub with your current tap water and don’t bother increasing the CH. As long as you have about 50ppm or more of CH, you won’t get any foaming in the water. Adding additional calcium does nothing for the hot tub.

I think this was exactly what happened. I have since refilled and now am able to accurately test. I was too generous on my application on Calcium carbonate. 9000 gallons is more forgiving than 350 gallons with application of chemicals.

The Taylor test kit appears to precipitate the indicator solution at very high PPM concentrations of calcium. This would track with your comment about the test having an upper range of 800 PPM.

Thanks all for your input.

 

[Maverick23]

So your reagents appear good as matching to the county measurement (using a 10ml sample has 25ppm per drop - so higher than 50 and no more than 75)

If you put fresh water in hot tub then your test should measure about the 75ppm again.

Just curious, why is the pool so high in CH? Do you use cal-hypo for sanitation?

I added additional calcium carbonate and added too much.

 

[JoyfulNoise]

The Taylor test kit appears to precipitate the indicator solution at very high PPM concentrations of calcium. This would track with your comment about the test having an upper range of 800 PPM.

The chemical is an azo-dye complexometric indicator (ie, an organic molecule that binds to divalent metals). It is common for these types of chemicals to precipitate out of aqueous solutions as they have low solubility and, when attached to a metal ion, their solubility decreases even more. So in a saline (salt rich) environment with high mineral hardness, these dyes can easily precipitate out which is why you see them as floating specs in the water sample. When dealing with high hardness levels, it is often best to dilute the test sample with a know ratio of mineral free (distilled and deionized) water. As long as you are reasonably good at measuring and diluting the water sample, the accuracy will not be terribly affected.