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KEEP THIS MANUAL
9.
GOOD THINGS TO KNOW ABOUT POOLS & WATER
Water Balance
In order to maximize your pool enjoyment and at the same time protect costly pool
equipment, ideal values for the various pool parameters have been established
by the American National Standards Institute (ANSI) and the National Pool & Spa
Institute (NPSI).
Suggested NSPI Standards – Pools and Spas
MIN
IDEAL
MAX
pH
7.2
7.4 – 7.6
7.8
Free Chlorine, ppm
1.0
1.0 – 3.0
3.0
TDS, ppm
300
1000 – 2000
3000
Total Alkalinity, ppm
60
80 – 100
180
Calcium Hardness, ppm
150
200 – 400
500-1K
Cyanuric Acid, ppm
10
30 – 50
150*
*Except where limited by the Health department requirements, often to 100 ppm. (ppm = parts per million)
Water & pH
pH is the single most important element in swimming pool water chemistry. It af-
fects every other chemical balance in pool water. pH is a measure of hydrogen ion
(H+) concentration in water. It indicates the relative acidity or basicity of pool water.
pH is measured on a scale of 0 (strong acid) to 14 (strong base) with 7 being the
neutral pH.
In pools, a slight alkaline pH of 7.4 to 7.6 is ideal because it is the most comfortable
to the human eye and provides for optimum use of free chlorine while maintaining
water that is noncorrosive or scale forming.
What happens when the pool is too acidic? (pH is low)
• If your pool surface is plaster, the water will begin to dissolve the surface, creat-
ing a roughness which is ideal for algae growth. A similar result occurs in the
grout of tiled pools.
• Metals corrode - this includes pool equipment, pipe/pump connections, etc.
• As the pool walls and metal parts corrode, sulfates form. These sulfates are
released from the water onto the walls and floor of the pool causing brown and
black stains.
• Chlorine, which is used as a disinfectant in the pool water, is activated and lost to
the atmosphere very quickly.
• When we swim, our eyes and nose burn; swimwear fades and perishes.
What happens when the pool is too alkaline? (pH is high)
• The calcium in the water combines with carbonates and forms scale. This calcifi-
cation is seen most at the waterline, where it traps dust and dirt, turning black.
• The water starts to become cloudy or murky and loses its sparkle.
