Water that is not balanced — that is too acidic or too basic — can cause bather discomfort, cloudy water and damage to the pool and spa surfaces and equipment.
Stable water quality is based on proper use of the saturation index and formula. Bringing the pH, total alkalinity, total hardness, temperature, and total dissolved solids together using the index gives you the complete answer to pool water quality and balance. Various factors are used to calculate saturation levels. The results provide you the information needed to balance the pool and correct its corrosive or scale forming condition.
SATURATION INDEX = pH + TF + CF + AF + 12.1
pH: measured from test kit
TF: temperature factor, measured at pool
CF: calcium hardness, measured from test kit
AF: alkalinity factor, measured at pool
BALANCE: Water with a calculated index between: -0.5 and 0.5 is balanced.
OVER: 0.5 is scale-forming (over-saturated).
BELOW: -0.5 is corrosive (under-saturated).
A swimming pool has a F.A.C. of 2.0 ppm, total available chlorine (T.A.C.) residual of 2.5 ppm, with a pH of 7.0. The total alkalinity is 50 ppm and calcium hardness is 200 ppm; water temperature is 84 F. Is the pool water scale-forming?
SATURATION INDEX = (pH) 7.0 + (TF) 0.7 + (CF) 1.9 + (AF) 1.7 + 12.1 = -0.8
In this equation we are given the pH of 7.0.
Table 1 shows that when:
■ Water temperature is 84 F, the temperature factor (TF) is 0.7.
■ Calcium hardness is 200 ppm the CF is 1.9.
■ Alkalinity is 50 ppm, the AF is 1.7.
The equation solution equals -0.8. From the saturation index information above, this indicates a corrosive water condition.
Use our handy online LSI Calculator.
Our LSI Calculator lets you punch in the numbers from your pool water test kit, then receive an instant readout of your water’s LSI value. If the result is in the sweet spot between –0.3 and +0.3, your water is being as kind as possible to your equipment. Fortunately, if it’s not, there are simple ways to fix it.
Easy ways to recover your balance.
•Raise your LSI by adding sodium bicarbonate or baking soda.
•Lower your LSI by adding muriatic acid.
Red Square Pools serving S. Nevada, Las Vegas, Henderson & Summerlin. Services include weekly cleaning, repair, equipment sales, acid wash and tile cleaning.