The
Saturation Index - The
key to water balance
The Saturation
Index sometime called the Langlier Index or Water Balance Index,
is the driving force for determining if a pool is balanced. An un-balanced
pool is either acidic(corrosive) or basic(scaling) . The index determines
whether the water is balance or not. Water can be balanced, even though
it may not meet "traditional" values for being balance. Local
water supplies have an influence on the water chemistry.
Saturation Index Equation: SI = pH + TF + CF + AF -TDS
|
TF
CF
AF
TDS
|
=
Temperature Factor in degrees Fahreheit
= Calcium Hardness Factor in ppm Calcium Carbonate
= Alkalinity Factor
= 12.07 for Total Dissolved Solids(TDS) factor for TDS 500ppm
= 12.10 for Total Dissolved Solids(TDS) factor for TDS 1000 ppm
= 12.2 for Total Dissolved Solids(TDS) factor for TDS 1000-2000ppm
= 12.2 for Total Dissolved Solids(TDS) factor for TDS >2000
ppm |
| To
Calculate the Saturation Index, test for pH, temperature, calcium
hardness and total alkalinity. Find the cooresponding values in the
chart below and enter those into the equation. Accepatable values
are -0.3 to +0.5, ideally 0.0 to +0.5. |
|
Temperature
|
Calcium
Hardness
|
Total
Alkalinity
|
|
Temp
|
TF
|
ppm
|
CF
|
ppm
|
AF
|
|
32
|
0.0
|
5
|
0.3
|
5
|
0.7
|
|
37
|
0.1
|
25
|
1.0
|
25
|
1.4
|
|
46
|
0.2
|
50
|
1.3
|
50
|
1.7
|
|
53
|
0.3
|
75
|
1.5
|
75
|
1.9
|
|
60
|
0.4
|
100
|
1.6
|
100
|
2.0
|
|
66
|
0.5
|
150
|
1.7
|
150
|
2.2
|
|
76
|
0.6
|
200
|
1.9
|
200
|
2.3
|
|
80
|
0.7
|
300
|
2.1
|
250
|
2.4
|
|
94
|
0.8
|
400
|
2.2
|
300
|
2.5
|
|
105
|
0.9
|
800
|
2.5
|
600
|
2.8
|
|
|
Sample Resuts:
pH 7.4
Temperature= 83'F
Calcium Hardness = 300ppm
Alkalinity = 100 ppm
TDS = 800 ppm
The Calculation:
SI = 7.4 + 0.7 + 2.1 + 2.0 - 12.1 = 0.1
The SI falls within an acceptable range and
the water is balanced.
|
|
