Too High, Too Low – Easy Pool Chemical Balance

Pool chemical balance is essential to your successful operation. Below, we explore all of the common (and in some cases, less common) chemical values you’re tasked with quantifying.  Read further to find out just what happens when those values are too high or too low.

Chlorine and Bromine*

Acceptable Range: 1-5 ppm (2-10 Spas)

Ideal Range: 2-4 ppm (3-5 Spas)

The Basics: Chlorine and bromine are oxidizers and sanitizers needed to keep your water safe. At an appropriate level they reduce the likelihood that someone will get sick from your pool.

Too High: High levels of chlorine can cause irritation to bathers and can cause damage to hair, bathing suits and pool equipment. Chlorine is also an expensive chemical, and overuse will have a negative impact on your bottom line.

Too Low: When it’s doing its job, chlorine is responsible for eliminating algae, bacteria, viruses and protozoa in the pool. Not having enough chlorine puts your swimmers in an unnecessarily perilous position.

Note: For ideal and acceptable bromine ranges, simply double all of the above quantities.


Acceptable Range: 7.2-7.8

Ideal Range: 7.4-7.6

The Basics: pH is the measure of acids versus bases. Water that is close to a neutral pH creates a comfortable swimming experience while efficiently utilizing sanitizing chemicals.

Too High: High pH will lead to scale forming water that is more likely to clog filters, heaters and circulation equipment. The oxidation efficacy of chlorine diminishes as pH rises. Add to that decreased bather comfort and you’ll want to stick to ideal ranges.

Too Low: Water that is more acidic (lower pH) will also negatively impact bather comfort. When your pH is low, your water is more likely to be corrosive, damaging pool equipment, structures and surfaces.

Total Alkalinity

Acceptable Range: 60-120 ppm

Ideal Range: 80-100 ppm

The Basics: Alkalinity is the anchor that keeps pH in its place. Get your alkalinity right, and your pH is much easier to control.

Too High: When your alkalinity is too high your pH becomes difficult to adjust. This is commonly referred to as pH lock.

Too Low: If you’re alkalinity is too low pH changes can occur rapidly and frequently. This is commonly referred to as pH bounce.

Calcium Hardness

Acceptable Range: 150-1000 ppm (100-800 spas)

Ideal Range: 200-400 ppm (150-250 spas)

The Basics: Water seeks out calcium, and it can find it in and around your pool. Water can draw calcium from structures and surfaces like your concrete or plaster walls, pool paint, tile and grout or exposed heater elements. Feed your pool water the calcium it wants before it challenges the structural integrity of your pool.

Too High: Calcium can come out of solution depositing on your pool surfaces, clogging pipes and filters, and may cause cloudy water conditions.

Too Low: Water with low calcium hardness is corrosive and aggressively removes calcium from exposed pool surfaces.

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Combined Chlorine

Acceptable Range: 0-.4 ppm (0-.5 Spas)

Ideal Range: 0

The Basics: Used chlorine is best measured as combined chlorine. Combined chlorine is responsible for the gaseous byproduct chloramines – the nasty smell associated with poorly treated swimming pools.

Too High: High levels of combined chlorine lead to high levels of chloramines, and a bevy of bather discomfort and facility decay issues will follow. For more on chloramine reduction, click here.

Too Low: N/A

Total Dissolved Solids

Acceptable Range: 0-1500 ppm over start up

Ideal Range: N/A

The Basics: TDS is the measure of all matter added to the pool water. This can include typical chemicals, specialty chemicals, swimmer waste and debris.

Too High: High TDS generally correlates with high levels of organic contaminants and may also act an indicator of the age of your pool water. This added material may increase the consumption of your disinfectants by fueling the growth rates of algae and bacteria. Higher TDS also directly correlates with higher conductance of water which can lead to galvanic corrosion (rapid aging of submerged metal components). Elevated TDS levels can change the way light reflects and refracts off of water, causing it to look dull. When TDS levels are high, the best solution is partial replacement of the pool water.

Too Low: N/A

Cyanuric Acid

Acceptable: 20:1 Ratio to Free Chlorine (CMAHC)

Ideal Range: N/A

The Basics: Cyanuric Acid (stabilizer) protects free chlorine against the effects of ultraviolet rays from the sun. As an additive, or as part of a chlorine compound, CYA decreases the usage of chlorine at outdoor pools in environments with prominent sun exposure. New recommendations from the CDC’s Council for the Model Aquatic Health Code suggest that CYA should be used far more cautiously than previously advised. CYA decreases the effectiveness of chlorine and is now recommended to be used at a 20:1 ratio to chlorine or less. As an example, 1 ppm chlorine would allow for 20 ppm CYA. 2 ppm chlorine would allow for 40 ppm CYA.

Too High: Chlorine’s effectiveness may be significantly limited, allowing for an increased potential spread of recreational water illness. Stick to the CMAHC’s 20:1 ratio, or less if possible.

Too Low: N/A

Pool Chemistry can be a tricky subject, but it’s explained in depth at all of our Certified Pool and Spa Operator Courses.

Ready for more? Check out the full schedule here.