Calcium Hardness Testing in Swimming Pool Care

Calcium hardness testing has an end point that changes from red to a detectable blue. In case you don't know it, calcium is a metal and the calcium ion is what we are determining through the titration testing process.

Procedures in testing calcium hardness levels

Having a pool water testing kit is absolutely essential in your swimming pool care.

A test kit has test strips that actually help you accurately determine the correct level of calcium hardness in your swimming pool or spa.

The test kit ensures that your pool water feels right and that it is not causing any damage to your swimming pool equipment.

There are three elements that are involved in a calcium hardness test. The first of these test elements involves the use of a buffer solution called sodium hydroxide. In your Taylor test kit this buffer solution is marked R-0010. You will add 20 drops of this solution to your pool water sample during your testing. This allows you to raise the pH of your water sample.

When you raise your pH level high enough, any magnesium present in the water will be eliminated as an interfering factor. Furthermore, a higher pH level will cause the color saturation to be more distinct; therefore, making it much more easier to be seen. The second test element is a calcium hardness test solution which is marked R-0011 in your test kit.

When using this test solution, you will add 5 drops to your pool water sample and swirl it around to create the mix. If the water of your swimming pool is cold, it may take a little extra swirling to get a good mix. The usual color change in this test procedure, is from a light red to a sky blue as the titrant is added.

The last of the test elements to be utilized in your calcium hardness testing, is a test reagent. This reagent is marked R-0012 in your test kit. This is the reagent that you will add by counting the number of drops until your water sample changes color. This is also known as titrating your pool water sample.

When doing your calcium hardness test, make sure that you have good lighting. This allows you to properly observe your test results with accuracy. The number of drops added are multiplied by 10 to determined the level of your calcium hardness.

Understanding the results after testing your calcium hardness

If you don't understand the results of your testing, you will not be able to adjust your calcium hardness properly. The table below will help you to understand the results of your reading.

When pitting occursBalance or desired rangeWhen scale is formed
0 to 200 ppm250 to 500 ppm550 to 700 ppm

As you can see from the table above, the desired range for your calcium hardness level is 250 to 500 ppm. This is the ideal level for your swimming pools and spas. Keeping your calcium hardness at this range, will minimize any scaling or pitting in your pool plaster.

Consequences of low calcium hardness!

Because of the importance of calcium hardness to your water balance, the frequencies of your calcium hardness testing is very important. If the calcium in your pool or spa is too low, the water will begin to leach calcium from your pool surfaces. This problem will cause the pitting that you don't want.

When your calcium hardness is too high

The results of high calcium levels is cloudiness or scaling in your pool.

If you maintain your total alkalinity and pH levels at a slightly lower level, you can minimize the effects of high calcium hardness in your swimming pool or spa.

Factors that can cause an increase in your calcium hardness level

Please remember to take into account when doing your calcium harness testing that your source water, evaporation, and the addition of certain pool chemicals will cause your calcium content to increase.

Factors that cause a decrease in your calcium hardness

These are factors like:

  • Heavy rainfall
  • Leaks in your mechanical systems (plumbing)
  • Source water that is low in calcium content

There are cases where the results of a low calcium hardness reading can indicate that you are loosing a lot of water in you swimming pool. In a typical pool or spa environment, the calcium hardness should stay fairly constant. However if it continues to drop on a regular basis, then it could be a clear indication that you have a leak in your pool.

False readings of a calcium hardness test

There are times when you do a calcium test and get a false reading. Factors like small amounts of iron or copper in your water sample, may cause the end point of your result to be difficult to read. This false reading or end point can appear in one of two ways.

First off, the initial color after you add the indicator may never change. Secondly the end point color may turn purple; thus giving you a false test result. Remember that a normal color change will take place at the beginning of the titration, but the transition will fall apart.

With that said, make sure that you get the correct results from all of your calcium hardness testing.

Calcium hardness testing helps in regulating your calcium hardness level.

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