Testing for calcium hardness


Well-known member
Oct 30, 2018
Tucson, AZ
Does anyone have any recommendations for tools to measure calcium hardness? I'm currently measuring CH using my TF-100 kit's reagents, but run through them quickly due to the number of tests I conduct per week. I am curious whether there are any devices out there that utilize no reagent through electronic means or at least less reagent solution.


Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
How often do you test CH? You usually only need to test CH once a month. It does not change unless you lose water or have a plaster problem.


Aug 16, 2019
There are a few methods to test CH with a Taylor 2006 test kit.

From Tayor's manual:
Calcium Hardness Test
1. Rinse and fill large comparator tube to 25 mL mark with water to be tested.*
2. Add 20 drops R-0010. Swirl to mix.
3. Add 5 drops R-0011L. Swirl to mix. If calcium hardness is present, sample will turn red.
4. Add R-0012 dropwise. After each drop, count and swirl to mix until color changes from red to blue.
5. Multiply drops in Step 4 by 10. Record as parts per million (ppm) calcium hardness as calcium carbonate.
*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.

If you use the 10mL sample, you will use less reagent.


Well-known member
Oct 30, 2018
Tucson, AZ
The above mentioned test is how I've been testing the water for hardness, although I'm using a 10mL sample instead of 20.

I did a little research and have discovered that there are some electronic products, such as the Oakton WD-35613 which will make measurements via a calcium specific ISE probe (Ion Selective Electrode). Not the cheapest, though... $200 for the meter and then another few hundred dollars for the electrode.