A. C. Swimming Pools: Swimming Pool Water Fundamentals

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Swimming Pool Water Fundamentals

1. pH
Definition: pH is a value expressing the relative acidity or basicity (degree of alkalinity) of water.
Low pH can result in corroded metals, etched and stained plaster, eye/skin irritation, rapid chlorine loss, total alkalinity destruction.
High pH can result in cloudy water, scale formation, eye/skin irritation, poor chlorine efficiency, chloramine formation.
Points to Consider:
Generally, if the pH reading is high, the alkalinity of water is also too high. To lower the pH, add sodium bisulfate ( dry acid) or muriatic acid. When the pH has been lowered to around 7.2 let the water stabilize. (This may take 2-3 days.) Then test the pH level.
Adding sodium carbonate to raise the pH of water has a secondary effect as well--it raises alkalinity.
It is best not to add too large a quantity of chemicals at one time when adjusting for high or low pH. (For example, do not add more than 2 lbs. of dry acid, 2 lbs. of soda ash or 2 pts. of muriatic acid per 10,000 gallons for each treatment.) After each addition, let the water circulate for at least 2-3 hrs., and then add more chemical if necessary. This helps prevent wide swings in pH.
If your chemical test results are erratic or the pH test turns purple, chances are your sanitizer level (chlorine or bromine) may be too high and have a bleaching effect on tests, including those using DPD reagents. Verify high chlorine or bromine levels with an OTO test. It is often best to wait to perform reagent test until the chlorine or bromine level is allowed to fall below 5 ppm in the spa or pool.
Before taking a water test, all containers used for collecting, transferring, and testing should be rinsed several times with the water to be tested. Then immediately begin the test.

2. Alkalinity
Definition: Total alkalinity is the ability of water to resist changes to pH and is a measure of the dissolved bicarbonates in wate
Low Total Alkalinity can result in staining and etching of plaster, metal corrosion, pH bounce.
High Total Alkalinity can result in almost continual acid demand to keep pH in desired range, cloudy water, scaling.
Points To Consider:
When balancing water, first adjust the total alkalinity.
As alkalinity increases, pH tends to raise. When alkalinity is adjusted to a range of 80 to 130 ppm alkalinity, it maximizes the chances that the pH will hold in a range of 7.2 to 7.8
Since a pH sample of less than 7.2 almost always indicates alkalinity of less than 70 ppm,there needs to be an increase in alkalinity of at least 60 ppm to bring alkalinity within the correct range.
To maintain a balanced pH with the use of stabilized chlorinated isocyanurates, an alkalinity range of 110 to 150 ppm is recommended. A lower level range of 60 to 110 ppm is desirable when using chlorinating agents.
If soda ash is used to correct pH without an attempt to increase total alkalinity first, total alkalinity will almost always stay at an unsatisfactory low level.
If you use an acidic sanitizer (gas chlorine, trichlor, bromine tablets), maintain a high total alkalinity range 120 to 150 ppm. Each time the sanitizer is added to the water, the total alkalinity is lowered.)
When using an alkaline sanitizer (sodium hypochlorite, calcium hypochlorite, lithium hypochlorite,) keep a low total alkalinity range (80 to 100 ppm) since each time the sanitizer is added to total alkalinity will also be raised.

3. Calcium Hardness
Definition: Calcium Hardness (water hardness) is the amount of dissolved calcium (and magnesium) in the water.
Low Levels Of Calcium Hardness can result in metal corrosion, etching of pool plaster.
High Levels Of Calcium Hardness can result in cloudy water, mineral deposits, scale formation, discolored plaster.
Points To Consider:
Many areas in U.S. have hard water (high levels of calcium hardness), although some areas, such as the Pacific Northwest, Atlantic Seaboard and Gulf Coast, have soft water (low levels of calcium hardness).
Many municipal water treatment plants reduce the hardness in their water supplies. As a result, the water coming from the tap has a different hardness than the ground or surface water.
To increase the calcium hardness, calcium chloride can be added to the water. However, add it slowly until the proper level is reached since decreasing the hardness level is more difficult.
Calcium hardness can be decreased in a variety of ways including adding fresh water with a low calcium hardness level; using a chelating or sequestering agent; compensating for the high level by lowering the pH and total alkalinity; or using a water softener to remove the calcium.
If the water does not have enough calcium, the water will draw from other minerals, including copper, aluminum and iron. (this will result in equipment corrosion.
Inorganic hypochlorites increase water hardness. Any additional alkalinity adjustment in conjunction with sanitizer additions is therefore unnecessary and should be avoided. (this is especially true when calcium hypochlorite is used).

Glossary Of Terms
ACID DEMAND - The amount of acid required by your pool water to achieve the proper pH level.
ACID - A chemical that lowers pH and total alkalinity when dissolved in water by providing hydrogen ions. Hydrochloric Acid and Sodium Bisulfate are two commonly used acids.
ALGAE - A microscopic one-celled plant organism. These organisms are continually introduced into the pool by winds, dust storms, rain showers, and the like.
ALGAECIDE - A chemical used to kill algae.
ALGAE SPORES - Dormant algae residing in atmospheric conditions which are introduced into the pool water by rain showers, winds, dust storms, etc.
ALKALINE - A condition when water is above 7.0 on the pH scale.
BACTERIA - An unseen, but dangerous organism that occurs in all water. Bacteria is controlled by the use of disinfectants such as chlorine or bromine.
BALANCED WATER - Pool water which is maintained with a pH level between 7.2 and 7.6 and contains the proper total alkalinity, calcium hardness, and temperature to yield a Langelier Saturation index of plus or minus 0.5 is said to be chemically balanced.
BASE DEMAND - The required amount of soda ash to increase the pH level of pool water to the ideal range of 7.2-7.6.
BROMINE - A sanitizer and disinfectant that kills bacteria and prevents algae.
CALCIUM - Metal ion contained in water which can form salts such as calcium carbonate thus causing cloudiness or scaling. It usually exists due to improper balance of ph.
CARTRIDGE FILTER - A filter which utilizes a replaceable element and does not require backwashing.
CHLORAMINES - The chlorine in the water that has been weakened by the presence of contaminants such as urine, perspiration, etc. Eye irritation occurs when chloramines build up.
CHLORINE - A strong oxidizing agent available for use as a sanitizer and disinfectant to kill bacteria and prevent algae. May be obtained in granular or liquid form.
CHLORINE, AVAILABLE - Residual chlorine or chlorine that is available to destroy bacteria on contact.
CHLORINE DEMAND - The amount of chlorine required to destroy bacteria or algae.
CONDITIONER - A sun-screening chemical that reduces the loss of chlorine due to evaporation by the sun.
CORROSION - A chemical reaction caused by unbalanced water which causes metals or minerals to dissolve.
CORROSION RESISTANT - The ability of maintaining original surface characteristics under prolonged use.
CYANURIC ACID - A sun-screening chemical that reduces the loss of chlorine due to evaporation by the sun.
D.E. - “Diatomaceous Earth” is formed from the skeletons of microscopic water plants called diatoms. Each skeleton is an extremely porous framework of almost pure silica.
DPD - Technical name “Diethyl-P-Phenylene Diamine is an indicator reagent for chlorine testing. D.P.D. #1 tests for free available chlorine, D.P.D. #3 tests for total chlorine.
DRY ACID - A granular material used to lower the total alkalinity and Ph. Technical name Sodium Bisulfate.
EFFECTIVE FILTRATION AREA - The total surface area through which the design flow rate will be maintained during filtration.
ELECTROLYSIS - An electrochemical reaction that can result in a black stain near any metal used in the pool, such as ladders and pool lights.
EPA - Abbreviation for the Environmental Protection Agency.
FILTER AID - A type of finely divided media usually diatomaceous earth, processed perlite, or similar material used to coat a septum of diatomite type filter.
FREE CHLORINE RESIDUAL - The active chlorine level in pool water after the chlorine demand is satisfied.
G.P.M. - Gallons per minute.
HARDNESS - The amount of calcium, magnesium, iron, carbonates, sulfates, chlorides, nitrates, phosphates and silicates dissolved in the water. Scale deposits are formed when there are high levels of hardness present in pool water.
HYPOCHLORIOUS ACID - The free state of chlorine which actually destroys the bacteria and other organic wastes.
IMPURITIES - Any substance dissolved or suspended in water which alters the chemical and/or physical properties of the pure substance.
IODINE - A disinfectant and sanitizer that kills bacteria and prevents algae growth.
LANGELIER SATURATION INDEX - A formula developed by Dr. W.F. Langelier to determine the scale forming or corrosive tendencies of water.
LITHIUM HYPOCHLORITE - Quick dissolving, leaves no residue, 35% available chlorine.
MAGNESIUM - A dissolved mineral in swimming pool water. Contributes to water hardness and turbidity.
MURIATIC ACID - Hydrochloric acid in liquid form used for lowering total alkalinity of pH.
N.S.F. - National Sanitation Foundation.
OTO - An indicator reagent used with a test kit to determine the amount of chlorine in the water.
PARTS PER MILLION (PPM) - A measurement used to calculate the “Parts per million” or “pounds per million pounds” of the chlorine, hardness, and alkalinity of your pool water.
PH - The total of the acisic or alkaline particles in the water. The recommended idea range is pH 7.2 to 7.6.
PHENOL RED - An indicator reagent used with your test kit to determine the pH of pool water.
SAND FILTER - Type of filter using silica sand media for filtration, requires backwashing.
SCALE - A crusty substance usually gray, white, or brown that attaches itself to tile or plaster. Normally caused by a calcium carbonate (hard water) buildup.
SHOCK TREATMENT - Super-chlorination accomplished by adding 5-10 times the normal chlorine dose every seven to ten days to help free up the regular chlorine.
SKIMMER - An inlet at water level to catch large debris thus preventing damage to the filter.
SODA ASH - A chemical, Sodium Carbonate, that raises pH.
SODIUM BICARBONATE - A chemical, Baking Soda, that raises total alkalinity and has little effect on pH.
SOLIDS - Dissolved and suspended matter in water. Dissolved solids are those which are in solution and not removed by filtration; suspended solids are removed by filtration.
STABILIZER - A chemical when used properly is a very effective control of chlorine. Inhibits the ultra violet rays of the sun from destroying the chlorine. Cyanuric acid is normally used as a stabilizer in swimming pool water.
T.D.S. - Total dissolved solids. High levels of T.D.S. which build up in pools due to evaporation interfere with chlorination.
TEST REAGENTS - Various chemicals that make a test kit work. In either liquid or dry form they change colors or indicate readings on the test kit’s scale.
TOTAL ALKALINITY - The number of carbonates, bicarbonates, and hydroxides, measured in ppm that are present in pool water.
TURBIDITY - Cloudiness caused by fine visible and/or colloidal material in suspension which interferes with the normal passage of light through liquid.
TURNOVER - The period of time required to circulate a volume of water equal to the water volume of the pool.
VELOCITY - The rate of movement of water measured in feet per second or gallons per minute.
WORKING PRESSURE - The maximum operating pressure recommended by the manufacture.

A.C. Swimming Pools
3621 Messanie * St. Joe. Mo. 64507
816-232-9198 Fax: 816-232-7979

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