Pool Water Balance

In the old days, before we had computer-assisted water testing and test strips, we had to actually titrate tests, count drops and look for color changes,  This is the way the route techs still do water testing.  I still believe it is the best method for testing and it teaches everyone what water balance is and how to actually balance a pool.

The purpose of water testing is to be able to change the water chemistry so the water is “balanced”.  This means that the water is neither scaling or corrosive, but in perfect balance.  If water is not balanced, it will either scale or corrode surfaces that it is in contact with.  Unbalanced water will hurt the pool finish and will, in most cases, lead to staining. 

Water balance is a combination of four test parameters.  These are pH, total alkalinity, calcium hardness and water temperature.  These four conditions must be compared to each other, and the results will determine whether or not the water is in balance.  This comparison is called the Langlier Index.  It is shown best on the Taylor Watergram which is inside every Taylor test kit.  On the Watergram, you line up the various test results and it will tell you if the water is in or out of balance.  It may be necessary to make changes to the water in order to put it into balance.  Obviously, you cannot change the water temperature, and we must keep the pH in a specific range of 7.2 to 7.6.  Therefore, we need to make adjustments elsewhere to balance the water. 

Each of you needs to get the wheel from one of the Taylor test kits and do some experimenting.  Our computers use this same principle to balance the water, but you need to know how it actually works. 

Suppose we have a calcium of 100, an alkalinity of 100, and water temp of 70.  The Watergram shows that we would need a ph of 7.8 to 7.9.  That pH is too high, so we need to make adjustments.  If we do nothing else but raise the calcium to 220, now the balance shows a pH of 7.5, which is perfect.  In this example, if the water temperature is 90, we only need to raise the calcium to 160-180 to achieve water balance. 

Remember, you can’t change the temperature and you can’t lower the calcium, so you need to affect the balance by changing the pH, alkalinity or raising the calcium.  The place to start is always with alkalinity.  It needs to be in the 90 to 120 range.