Code
AQUATIC VENUE water shall be chemically balanced.
Annex
Water balance is an important part of proper AQUATIC VENUE operation and maintenance. As such, the Langelier Saturation index (LSI) is a useful tool for MONITORING the corrosive or scale-forming tendencies of AQUATIC VENUE water. Although there is little scientific literature on the LSI and AQUATIC VENUE water, it is common industry practice to use this index.
The LSI formula is: LSI = pH + TF + CF + AF – TDSF
* pH Obtained by testing the POOL or SPA water.
* TF Temperature Factor - using MAHC Annex Table 5.7.4.6 (below), look up the actual AQUATIC VENUE water temperature at the time of sampling, in order to obtain the appropriate TF value.
* CF Calcium Hardness Factor - determine the PPM (MG/L) of calcium hardness (CH) in the water sample. Using the MAHC Annex Table 5.7.4.6 (below), use the appropriate calcium hardness (CH) reading, in order to obtain the appropriate CF value.
* AF Total Alkalinity Factor - determine the PPM (MG/L) of total alkalinity (TA) in the water sample. Using the MAHC Annex Table 5.7.4.6 (below), use the appropriate total alkalinity (TA) reading, in order to obtain the appropriate AF value.
* TDSF Total Dissolved Solids Factor – If the TDS of the water is less than 1,000 PPM (MG/L), use the factor of 12.1. If the TDS of the water is greater than 1,000 PPM (MG/L), use the factor of 12.2.
Note: Use the TF, CF, and AF factors closest to your actual reading.
Total Dissolved Solids
A generally accepted level for TDS in AQUATIC VENUES is 1,500 PPM (MG/L) above the TDS level in the fill water. For AQUATIC VENUE using CHLORINE GENERATORS, startup TDS level should be measured on the initial fill after adding the salt for the CHLORINE generator. Additional research needs to be done to determine TDS in salt water AQUATIC VENUE, and its impact on water quality.
Total dissolved solids (TDS) are a measure of the overall quantity of matter in the AQUATIC VENUE that is not water. This matter includes such things as minerals (calcium, magnesium, etc.), chemicals, body oils, sunscreen, etc. that are not removed by filtration.
There is only one state that has a maximum required TDS level (2,500 PPM (MG/L)). However, there is no known scientific data that substantiates any value as a maximum level. The 1,500 PPM (MG/L) level is utilized based on the fact that as the concentration of these materials increases in the AQUATIC VENUE they can result in staining, cloudy water, decreased effectiveness of disinfectants (by up to 50%), and an enhanced environment for the growth of algae. Excessively high TDS levels (greater than 5000 PPM (MG/L)) may require more drastic measures such as a complete AQUATIC VENUE drain and refill, or additional water filtering, as a complete water drain may damage some AQUATIC VENUE.
It is also important to note that the salt required by saltwater chlorination systems will substantially increase the TDS level. Therefore, in saltwater AQUATIC VENUE, it is best to consider the TDS level after the required amount of salt has been added to a freshly filled AQUATIC VENUE as the baseline level.
Table 5.7.4.6 Langelier Index Conversion Chart
TF
CF
AF
Temp °F/°C
TF
CH PPM (mg/L)
CF
TA PPM (mg/L)
AF
32°F / 0°C
0.0
5
0.3
5
0.7
37°F / 3°C
0.1
25
1.0
25
1.4
46°F / 8°C
0.2
50
1.3
50
1.7
53°F / 12°C
0.3
75
1.5
75
1.9
60°F / 16°C
0.4
100
1.6
100
2.0
66°F / 19°C
0.5
150
1.8
150
2.2
76°F / 24°C
0.6
200
1.9
200
2.3
84°F / 29°C
0.7
300
2.1
300
2.5
94°F / 34°C
0.8
400
2.2
400
2.6
105°F / 41°C
0.9
800
2.5
800
2.9
128°F / 53°C
1.0
1000
2.6
1000
3.0
Water balance should fall within the range of –0.3 to +0.3, as determined by the Langelier Saturation index.
A Low Langelier Index (a value less than –0.3) can result in corrosion, BATHER irritation, and discomfort. AQUATIC VENUE water may cause etching, pitting, dissolving, and staining of walls, grouting, and plumbing.
LSI Decreases as:
* Stabilizer Increases, and
* Total Dissolved Solids Increase.
A High Langelier Index (a value greater than +0.3) can lead to scale formation, cloudy water, filtration problems, heater problems, loss of CHLORINE efficiency, and BATHER discomfort. AQUATIC VENUE water may deposit excess minerals on the POOL and equipment. Scale generally appears as white or lightly colored rough blotches on the AQUATIC VENUE walls. It also adheres to other objects in the pool, piping and filter system. Scale can restrict water flow, shortening filter runs and reducing filtration efficiency.
LSI Increases as:
* Temperature Increases,
* Total Alkalinity Increases,
* pH Increases, and
* Calcium Hardness Increases.
A small positive value is preferred over a negative value because a slight scale layer provides some protection, and is less harmful than corrosion, which causes permanent damage to mechanical and structural components.
Langelier Indexes can be adjusted to the -0.3 to +0.3 range by:
* Adjusting the pH to 7.2 to 7.6, and
* Adjusting the total alkalinity to 60 to 180 PPM (MG/L), and
* Adjusting the calcium hardness to
o 200 to 400 PPM (MG/L) for a masonry POOL or SPA, or
o 80 to 200 PPM (MG/L) for a vinyl or fiberglass unit.
While it is always possible to lower the pH, it is not as simple with the total alkalinity or calcium hardness. Lowering the total alkalinity will usually lower the pH as well. Lowering the calcium hardness is not always possible, given the variation in hardness of the fill water. In situations where the calcium level is high, attention should be paid to lowering the pH and / or total alkalinity in order to improve the LSI.
It is not always possible to get the pH and total alkalinity within the proper range, due to the nature of the dissolved minerals. pH is the more important parameter, and should be maintained within the proper range.
If the AQUATIC VENUE is outdoors, and uses stabilized CHLORINE, in order to get a more accurate reading of the LSI, it is recommended that 30% of the cyanuric acid reading be deducted from the total alkalinity test result.