WATER CHEMISTRY

There are three factors that affect your pool’s water quality:

• Physical Factors

• Chemical Factors

• Biological Factors

PHYSICAL FACTORS

Physical factors are comprised of the filtration, circulation and other factors such as oily wastes and the appearance of pools walls and equipment inside the pool. Filtration refers to the pools ability to physically remove debris / contaminants from the water. The different types of filtration systems are cartridge, sand and diatomaceous earth (DE).

Each system has its pros and cons but are all effective at filtering the pool water. More important is how you manage your filtration system since the goal of these pieces of equipment is to prevent a problem rather than reacting.

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• Circulation is the process of constantly moving water through the various sanitation and filtration systems in the pool.

• Turnover is how long it takes for the pool to pass through the filtration system and sanitation systems.

Other factors are composed oily wastes brought on by bather load and micro debris that are too small to be filtered by your filter. Oily wastes show up as an unattractive scum line along the waterline. Micro debris can cause a slight haze to the water. Both of these factors will require a chemical supplement to manage such as a clarifier, flocculation or an enzyme digestive product.

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CHEMICAL FACTORS

Proper chemical treatment prevents a wide range of issues such as staining, scale formation, cloudy water and corrosion of pool surfaces and equipment. It also ensures your sanitizer (such as chlorine) performs as it should.

The five chemical factors that affect water quality:

 

• PH: 7.2 – 7.8

• Total Alkalinity: 80 – 120 PPM

• Calcium Hardness: 100 – 400 PPM

• Stain Producing Minerals: AbsenT

• Total Dissolved Solids (TDS): 250 – 1500 PPM

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PH, total alkalinity and calcium hardness along with temperature will determine your overall water balance. Water balance refers to the water’s tendency to be either corrosive or scale forming. When those 3 factors are too high, it can cause scale to form on the pool walls as well as cause the water to be cloudy. When the water is corrosive, those above factors are typically too low and will cause destruction to your pool walls and equipment.

pH

pH (aka potential Hydrogen) refers to the degree of activity of an acid or base in the water. pH is measured on a scale of 0 to 14 with 0 to 7 being acidic and 7 to 14 being base (or alkaline). It is recommended the pH be kept between 7.2 and 7.8. This is ideal for swimmer comfort but also allows your chlorine to operate at optimal level without using too much. Although chlorine sanitizes better when the pH is lower, it becomes unstable and will result in larger consumption. A source of pH fluctuation can also be your sanitizer. Depending on the pH, your sanitizer can help you figure out the source of fluctuation. Di-chlor (granular chlorine) has a pretty neutral pH of 6-7 while sodium hypochlorite (liquid chlorine) has a ph of 13-14. Your typical tri-chlor chlorine tablet has a pH of 2-3.

Total Alkalinity

Total alkalinity refers to the ability of the pool to resist change in pH. TA acts as a buffer that allows the pH to resist change. It is recommended that the TA be maintained between 80 and 120 PPM. When the TA is low, the pH will be erratic and difficult to control. When the TA is too high, it can cause scaling and the pH will drift upward. A unique element of TA is that the same chemical that is used to lower TA is the same chemical that will lower pH so it is a balancing act when addressing high TA. When using acid, it is important you make small adjustments over a longer period of time. When needing to raise TA, you can add the entire dose needed to get to the desired range.

Calcium Hardness

Calcium hardness is the sum of all calcium dissolved in the water. A High calcium levels is called “hard” water while low calcium level is “soft” water. High levels of CH can result in cloudy pools and scaling. Low CA can cause the water to become destructive by looking at other sources within in your pool for the mineral. These candidates can be your pools plaster, the heat exchanger inside your heater or metal fittings located within in the pool. The ideal range for CA is between 100 - 400 PPM. To raise CA, you can add CA increaser. There is no chemical to lower CA. The only way is through dilution, so water would need to be removed and added back into the pool.

Stain Producing Minerals

Iron, copper, and manganese are the most common sources of stains in your pool. The source of these minerals is typically your fill water. A simple test can determine the type and amount of the mineral in your fill line. All of the problems associated with these metals can be prevented by using a sequestering agent.

Iron: When iron reacts with chlorine, it will turn a rusty red color. It can as little as .01 PPM to cause staining.

Copper: Stains ranging in color from green, to blue green, to black are typically caused by copper. Copper can be from your fill water but can also be sourced from your heat exchanger in your heater or copper based algaecides.

Manganese: When manganese is present, the water can turn pink to a deep purple depending on how much is in the water. This is typically sourced through your water supply.

Total Dissolved Solids (TDS)

TDS is the sum of all materials in the water. When the TDS is high, it can cause cloudy water, difficulty in maintaining water balance, reduction in sanitizer activity and foaming. The only way to lower TDS is by dilution through water replacement. TDS is not a typical problem found in colder climates since your water is drained during winterization thus diluting the TDS.

BIOLOGICAL FACTORS

Sanitization, shock treatment and algae control are the key elements in keeping the water clean. Water balance helps keep the water clear while the above helps the cleanliness of the water.

Sanitization

Sanitization is the process of controlling the bacteria in the water so it’s safe to swim in.  There are several different types of sanitization but we will focus on the most popular which is chlorine.

 

 

Chlorine Types

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As noted above, there are a variety of chlorine types. Once the chlorine enters the water, it goes through another metamorphosis and becomes free or combined chlorine. A simple water test kit can be used to find out your free and total chlorine readings.

Free Chlorine: This is the most desirable form and is the form responsible for the actual sanitization. Free chlorine is highly reactive and will attach to bacteria and other wastes.

Combined Chlorine: Once free chlorine reacts with bacteria or other wastes, it becomes combined chlorine. This form of chlorine has little to no sanitizing ability and is also responsible for the chlorine smell that many people associate with “too much chlorine”. Not only is the odor unpleasant, it can cause skin and eye irritation. Combined chlorine should be kept to a minimum. The combined chlorine reading should not exceed 0.2 PPM. To manage your combined chlorine, use a non-chlorine shock. This will change your combined chlorine back into free chlorine.

Total Chlorine: This is the sum of the free and combined chlorine. There is no test for combined chlorine so you would take the total chlorine minus the free chlorine and the remainder would be the combined chlorine.