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An ideal pH range for most swimming pools is between 7.2 - 7.6 S.U.
An ideal swimming pool range is 7.2 - 7.6 units (mildly basic). Before adjusting your pH, ensure your total alkalinity concentration is balanced.
To increase pH the recommended chemical is soda ash/washing soda (sodium carbonate). Baking soda (sodium bicarbonate) can also be used to raise pH, but use caution as this will also increase the total alkalinity concentration. It will also require using more chemical than soda ash, and the amount required can't easily be calculated.
When using baking soda to adjust pH, instructions generally advise on adding in 4-8 lbs. increments for pH levels less than 7.2, followed by re-testing in 24 hours
To decrease pH use muriatic acid (liquid) or sodium bisulfite (dry).
Muriatic acid or sodium bisulfite should be added slowly to the deep end of the pool away from pool walls and fittings, while the filter cycle is off - restart filter cycle after 10 minutes. Muriatic acid should not be added to the skimmer basket.
pH is a measure of acidity on a logarithmic scale of 0 to 14, with pH 7 being neutral.
Dangers of Low pH:
Dangers of High pH:
An ideal free chlorine range is from 1.0 - 3.0 mg/L (ppm).
A chlorine disinfected swimming pool should maintain a concentration of free chlorine (FC) between 1-3 mg/L (ppm).
Conversely, a low combined chlorine (CC) concentration is ideal (0-0.5 mg/L).
An elevated chlorine concentration poses an unsafe condition for swimmers. Pool should remain unoccupied until the concentration of
chlorine decreases with time. Elevated CYA concentrations (especially above 80-100ppm) can significantly impact the effectiveness of FC while still
yielding an unusually high FC concentration (i.e., 5+ mg/L).
Chlorine is added to swimming pools for biological disinfection. The oxidative properties of chlorine destroy the cellular walls of
microorganisms and bacteria rendering them harmless.
As chlorine is consumed or combined with other compounds (i.e., ammonia and nitrogen), its ability to disinfect is decreased. Free
chlorine is a measure of the chlorine 'still available' to disinfect organic matter.
Stabilized organic chlorine (i.e., trichlora-s-triazinetrione or trichlorisocyanuric acid) is suitable for weekly chlorination,
while inorganic chlorine (i.e., calcium hypochlorite or sodium hypochlorite) is used for daily chlorination and/or superchlorination ("shocking").
Take caution when using chlorine stabilized with cyanuric acid (CYA), as an imbalance of pool stabilizer (CYA greater than 100 mg/L) can
significantly decrease the effectiveness of chlorine, and can only be removed by draining/diluting the pool.
A total alkalinity in the range of 100 - 120 ppm is ideal.
Total alkalinity should be maintained at a minimum concentration of 80 mg/L. Concrete and gunite pools should be maintained between 100-120 mg/L, while vinyl and fiberglass pools should be maintained between 110-150 mg/L.
Baking soda (sodium bicarbonate) is the best option for increasing total alkalinity. Baking soda can be added by casting into the deep end pool with the filter cycle operating. If adding directly to skimmer basket, add in small quantities to prevent damaging your equipment.
To decrease alkalinity, decrease the pH by adding either muriatic acid or sodium bisulfite. Chemical should be added slowly to the deep end of the pool away from pool walls and fittings, while the filter cycle is off - restart filter cycle after 10 minutes. To prevent an unsafe condition, don't add more than
32 fl. oz. at one time - if more is required, add additional batches of 16 fl. oz. until reaching your target.
Total alkalinity is a measure of your pools total alkaline contributing ions (i.e., hydroxide, carbonate, bicarbonate). In other words, it's a measure of your pools acid buffering capacity. Alkaline ions in the water are consumed when acid is introduced, preventing a noticeable change in pH.
Dangers of Low Alkalinity:
Dangers of High Alkalinity:
The target calcium hardness concentration will vary for different applications.
An ideal concentration of calcium hardness is between 200-400 ppm or mg/L (expressed as a concentration of CaCO3).
Add calcium chloride or calcium chloride dihydrate to increase the calcium hardness - this will also raise the total hardness concentration an equal amount.
Calcium chloride should be added by casting the dry chemical into the deep end of the pool with the filter cycle operating. Do not premix or dilute with water, and
do not add to skimmer basket. Use caution as dissolving calcium chloride in water produces an exothermic reaction capable of generating a significant amount of heat.
The only way to decrease calcium hardness is by draining and adding fresh water to dilute the total concentration.
Calcium hardness is a measure of the concentration of dissolved calcium ions - this measure is typically expressed as an equivalent of calcium carbonate (CaCO3) in ppm or mg/L units. Dissolved calcium contributes a
significant portion of the total hardness concentration of your water. A low calcium hardness concentration can lead to damage and erosion in concrete and plaster pools as calcium ions in masonry are dissolved into the water.
Dangers of Low Calcium Hardness:
Dangers of High Calcium Hardness:
For chlorinated swimming pools, an ideal cyanuric acid range is between 30-50 mg/L (ppm).
Pool stabilizer can be added to increase the concentration of cyanuric acid. Add directly to skimmer basket during the filter cycle - add no more than 2 lbs. at a time.
Stabilizer should be added incrementally until achieving your target level. When using stabilized chlorine containing
CYA included within the formulation, consider that CYA levels will gradually drift upwards over time in proportion with chlorine usage. A CYA concentration of 30 ppm is sufficient for most applications; however, concentrations up to 50 ppm can help extend the lifespan of free chlorine especially if your pool receives a significant amount of direct sunlight.
The only way to decrease the cyanuric acid concentration is by draining and adding fresh water to dilute the total concentration.
Cyanuric Acid (CYA), otherwise known as pool stabilizer, is added to decrease the rate of degradation of
free chlorine as a result of ultraviolet light exposure. An effectively stabilized pool can increase the life
of free chlorine by up to 5x longer when compared to water without stabilizer.
In addition to being available as a stand-alone pool water additive, cyanuric acid is also included in
some stabilized chlorine products. Extended use of chlorine containing CYA as a stabilizer can cause CYA levels in your pool to drift upwards. When
using CYA stabilized chlorine, be sure to monitor your pool's CYA levels. Superchlorination (shocking) with dichlor-CYA granules can especially have an impact
on increasing your pools CYA's concentration.
Dangers of Low Cyanuric Acid:
Dangers of High Cyanuric Acid:
Enter the following to calculate LSI:
The saturation index of your pool water should ideally be between -0.3 and +0.3.
To increase the LSI, increase the alkalinity by adding baking soda (sodium bicarbonate).
To decrease the LSI, decrease the pH using muriatic acid or sodium bisulfite.
Dangers of LSI less than -0.3:
Dangers of High LSI greater than +0.3:
The Langelier Saturation Index (LSI) is an approximate measure of the degree of saturation of calcium carbonate in your water based on concentrations of alkalinity, calcium, total dissolved solids (TDS) and water temperature.
A target LSI of 0 is ideal, as it allows for fluctuations in pH and temperature.
A LSI less than -0.3 is considered corrosive. As the concentration of stabilizer in the water increases, the LSI decreases as the
higher acid concentration increases the water's corrosivity. Similarly, an increase in total dissolved solids will also lower the LSI.
A LSI greater than +0.3 is considered scale forming. An increase in LSI can be attributed to an increase in total alkalinity,
pH, calcium hardness, or temperature.