Calcium Hardness Problem

[Jdnbr]

Hello everyone! I'm a new pool owner who was having a disappearing chlorine problem. Bought the TF-100 test kit and slammed and I have now met the three criteria. The problem that I have is with the Calcium Hardness. Was using the pool store since the pool was finished 12/20. All CH readings were 510. When I test with the TF-100 I am getting 1500. I realize that the pool store may not be reliable but could they be that far off or am I doing something wrong. Pool Math says to drain 75% and refill. We have a small pool but it's still not cheap.
Thanks for sharing your knowledge.

 

[mknauss]

Welcome to the forum!
With the amount of rain you get it would be odd to get that high of a CH level. Have you been using calcium hypochlorite in the pool? Do you have scaling issues with your SWCG?
Do you use a Speedstir for your testing? I find that really necessary for doing the CH testing.
I suggest you read ABC's of Pool Water Chemistry.

 

[zea3]

Hi, welcome to TFP! Swirling is very important when you do the calcium test. If you don't use a speed stir, then you want to take your time swirling well between drops, instead of adding another drop after a couple of swishes.
Do you know the root of your calcium problem? Do you have very hard water? Former cal-hypo user?

 

[Jdnbr]

We have had very little rain in the past two months. I have not used any calcium hypochlorite. I removed and cleaned my SWCG when I started having the chlorine problem thinking it may be the problem but it had very little scaling. I do not have a speed stir. I do not know the source of the calcium problem. We had some paver work done outside the pool and with the cutting we did get some concrete dust on the solar cover. We took it off and washed it down but I am sure that some got in the water but the last 2 pool store tests were after that.
I will run the test again because I was adding after just a couple of swishes.

 

[mknauss]

I will run the test again because I was adding after just a couple of swishes.

Really take your time. Also, try using the metals interference process.
The sample may turn purple during the test, or go to blue for a moment and then turn back to red/pink. This is called a “fading endpoint” and is caused by interference from metal ions. If this happens, do the test again, but this time add five drops of R-0012 before adding any R-0010 or R-0011L. Remember to count the initial five drops in the total.
In extreme cases, a fading endpoint may occur even when adding five drops of R-0012 at the start. If that happens, mix pool water with an equal quantity of distilled water, test that, and then multiply the result by two.

Also be sure you are using a 10 ml water sample. Each drop of R0012 equals 25 ppm of CH level.

 

[Jdnbr]

We had a good long rain yesterday finally. I tested today using half pool water half distilled just to avoid so many drops. I took my time mixing each drop and came out with 18 drops x 2 = 36 drops = 900. Still very high but I don't seem to be having any scaling problems and our rainy season will be here soon. Is the half and half as accurate as full strength?

 

[mknauss]

Is the half and half as accurate as full strength?

There will be more error, but close enough.

If no scaling issues, just use rain water to refill after small drains when you can.

 

[Jdnbr]

Thanks for all of your help!