Balanced Water Testing

Posted by on Monday, December 19, 2011 Under: Pool Water Chemistry
Balanced water testing is something that you should be doing weekly in order to determined whether you pool water is 'balanced'. This refers to whether the water is corrosive or scale-forming.

Corrosive water will eat away at grout, pump seals, pipework etc. (basically, anything it comes into contact with). Scale-forming water does the opposite of corrosive and instead of eating away at things it will form a scale on it (you're likely to see the effect of this on the heating element of your kettle). This scale-forming can be a problem if it is allowed to build up on the pool circulation pipework etc.

The aim of good water quality management is to have water that is neither corrosive, or scale-forming (ie, balanced).

The test works like this:

Step 1. Carry out tests and note results for:
  • Calcium hardness
  • Total alkalinity
  • Pool water temperature  
  • Total dissolved solids
Step 2. Convert the results from the above tests to factors as indicated in the chart below (figures in red provide a worked example).

Step 3. Add the factors for temperature, calcium, alkalinity to the pH.

Step 4. Minus the factor for TDS from the figure obtained in step 3.

The ideal result is somewhere between 0.1 - 0.4. The pH level is the thing that has the most impact on water balance test results. A high pH would contribute to scale-forming water, a low pH would contribute to corrosive water. However,it is not advisable to start adjusting pH levels just to try and get good water balance results, as pH is a critical factor in the efficiency of your disinfection and coagulation, both of which are more important than water balance results. 

 A better way to a adjust water balance might be:

  • To increase: consider increasing the levels of calcium hardness, or total alkalinity, by adding calcium chloride or sodium bicarbonate respectively, depending on the results of those tests. Another option might be to reduce the TDS levels (if they are particularly high) by diluting with fresh water.
  • To decrease: Take a look at your pH result. If it's high, you need to decrease it anyway as your chlorine is not going to be as effective at higher pH levels.   

In : Pool Water Chemistry 

Tags: "calcium hardness" "calcium chloride" "total alkalinity" "sodium bicarbonate" "ph" "temperature" "water balance"