Measure Your Options
Determine the water care method that fits your lifestyle and maintenance needs.
By Debra Maurer
What’s the most important component of your swimming pool? The engineering maintains the structure, the design makes it beautiful, and the equipment keeps it operating properly—but what about the water? Clear, healthy water means your pool will be the ideal place for family fun and entertainment, as well as an attractive asset to your backyard.
Selecting a water care system starts with deciding which primary sanitizer you’d like to use. Chlorine, bromine, and biguanide are primary sanitizers because they maintain a residual in the water. Saltwater chlorinators are unique systems that use salt to generate their own chlorine, avoiding the need to add it by hand. You may also consider mineral, ozone, and UV light systems; these are supplemental sanitizers because they require small amounts of a compatible primary sanitizer to remain effective.
Chlorine is the most popular and least costly sanitizer. It is highly effective and available in stabilized forms (known as dichlor or trichlor) that contain cyanuric acid to prevent dissipation in sunlight. Unstabilized chlorine is more suitable for indoor pools where sunlight has little effect on chemicals in the water; if used in outdoor pools, you’ll need to add cyanuric acid separately. Chlorine also functions as an oxidizer or shock, meaning it will rid the water of organic elements such as sweat, sunscreen, and cosmetics. In saltwater pools with a chlorine generator, chlorine is produced from salt, which makes the water feel smooth and prevents the formation of strong-smelling chloramines.
Bromine is a chlorine alternative that is gentle on your skin and eyes, though it burns off easily in sunlight. Bromine is the most common primary sanitizer for hot tubs because they are covered when not in use, so the water receives little sun exposure. In addition, bromine holds up well in high temperatures and is effective at higher pH levels.
Biguanide is more expensive than chlorine and bromine, but it gives water a silky, smooth feel and does not irritate the eyes or have a strong smell. It also causes little or no fading to swimsuits. Another advantage is that biguanide is stable in sunlight and high temperatures, but pool owners must remember that it cannot be combined with chlorine, bromine, or mineral sanitizers. Biguanide pools must be oxidized with hydrogen peroxide; they are not compatible with monopersulfate or chlorine shock, which are used in chlorine and bromine pools.
Mineral sanitizers are available in two different systems: mineral cartridges and ionizers. Mineral cartridges fit into your filter and slowly release minerals into the water; they’re replaced about every four months. Ionizers are more expensive; these systems release silver, copper, or zinc ions that kill bacteria and algae. Both require certain levels of chlorine or bromine to keep water sanitized; however, some mineral cartridges are incompatible with bromine so be sure to read all labels.
Ozone is a short-acting oxidizer released into the water through an ozonator. Though technically not a sanitizer, ozone is often considered supplemental because it reduces the amount of primary sanitizer your water will require. Ozone must be used in conjunction with chlorine, bromine, or biguanide because it does not retain a residual. Ozonators are common in hot tubs, where owners also typically add bromine.
Ultraviolet light is a sanitizing option making its way into residential pools. Ultraviolet systems use UV light to destroy algae and chloramines. Like ozone, UV light maintains no residual and requires small amounts of a primary sanitizer.
Level Testing
Ideal Levels for Pools & Hot Tubs
Parameter Pools Hot Tubs
Free available chlorine (FAC) 1 – 4 ppm 3 – 5 ppm
Bromine 4 – 6 ppm 4 – 6 ppm
Biguanide 30 – 50 ppm 30 – 50 ppm
pH 7.4 – 7.6 7.4 – 7.6
Total alkalinity 80 – 100 ppm* 80 – 120 ppm
100 – 120 ppm**
Calcium hardness 200 – 400 ppm 150 – 250 ppm
Cyanuric acid (CYA) 25 – 50 ppm none
Total dissolved solids (TDS) should never exceed should never exceed
1,500 ppm 1,500 ppm
*When using unstabilized chlorine, such as calcium-hypochlorite
**When using stabilized chlorine, chlorine gas, or bromine as your sanitizer
Water Care Glossary
Key Terms to Understanding Water Care
Acidic: property of water with low pH; water is corrosive and can etch plaster, metals, and pool equipment
Alkaline: property of water with high pH; can cause scale
Biguanide (PHMB): sanitizer that gives water a silky feel; cannot be combined with bromine or chlorine
Bromine: sanitizer used primarily in spas and indoorpools; effective at higher temperatures and pH levels; unstable in sunlight
Calcium hardness: amount of calcium in the water; high levels can cause scale; low levels can cause corrosion
Chlorine: most common and highly effective sanitizer and oxidizer
Chloramine: byproduct formed when free chlorine combines with contaminants in the water; gives off a strong “chlorine smell”
Combined chlorine: made up of chloramines; does not sanitize the water
Cyanuric acid (CYA): stabilizer added to chlorine to prevent it from breaking down in sunlight; found in stabilized chlorine or added separately to water containing unstabilized chlorine; high levels can reduce chlorine’s ability to sanitize; not recommended for spas
Free available chlorine (FAC): amount of chlorine available to sanitize the water
Hydrogen peroxide: oxidizer used with biguanide
Oxidizer: burns up and removes oils, lotions, sweat, dirt, and other unwanted elements from the water
Ozone: oxidizer added to water via an ozonator; does not retain a residual; reduces the amount of primary sanitizer required for effective sanitization
pH: measure of water’s acidity or alkalinity
Potassium monopersulfate: non-chlorine shock that can be used with chlorine or bromine sanitizers
Sanitizer: kills and inhibits bacteria and algae growth
Scale: white film or deposits that form on water’s surface when pH and/or calcium hardness are too low; can plug up filters and circulation piping
Shock: oxidizer in concentrated form; added periodically to burn up sweat, oils, and other contaminants, especially after heavy use or a rainstorm
Total alkalinity: amount of alkaline elements in the pool; measure of water’s ability to resist changes in pH
Total dissolved solids (TDS): amount of bather waste and other solids that have accumulated in the water
Photo courtesy of Essig Pools, Inc.