Cyanuric Acid (Stabilizer)


The sun’s ultraviolet (UV) rays will make the chlorine in an outdoor pool dissipate quickly. In fact, an ideal level of chlorine in an “unstabilized” pool or spa can be lost in less than two hours on a bright sunny day, due to the UV rays of the sun. Cyanuric acid acts as a “stabilizer” that helps chlorine hold up better when exposed to the UV rays. You can think of cyanuric acid as blocking the effect that the sunlight has on breaking down the chlorine—kind of like a sunscreen for your pool.

You should maintain an ideal level of cyanuric acid, 30 to 50 ppm (mg/L), to prevent rapid chlorine loss. If the cyanuric acid level is too low, you may need to add more to the water. However, be advised that cyanuric acid will make the pH of the water lower (more acidic), so you may have to adjust the pH upward as well.

On the other hand, too much cyanuric acid will reduce the beneficial effect of your chlorine, leading to stains or cloudy water. Some chlorine compounds already contain an amount of cyanuric acid. If you are using dichlor or trichlor as your primary chlorine sanitizer, you are already introducing cyanuric acid along with the chlorine. If the cyanuric acid level is your pool or spa is too high, you will need to partially drain and refill with fresh water.

When you first fill your pool or spa, test the cyanuric acid level until you have added enough to reach the ideal range. After that, test cyanuric acid a minimum of once a month throughout the pool season. If you are using dichlor or trichlor, you will have to test cyanuric acid more frequently to ensure that the level has not exceeded the upper limit.





Water hardness occurs as an indirect side effect of various chemical compounds. Calcium and magnesium are the two primary minerals that make up hardness in water. Like alkalinity and pH, hardness affects the tendency of the water to be corrosive or scale-forming. (Scale is a deposit that forms on pool walls and equipment when the mineral content of the water is too high.) By maintaining the ideal ranges for hardness and alkalinity, you can keep scale formation to a minimum.

Low hardness levels require immediate attention! They can be very dangerous to your system. Water that is not properly saturated with hardness—water in which the hardness level is too low—will be very corrosive, causing significant damage to metal pipes and fixtures as well as plaster. You must be sure to balance hardness before adding any sanitizer to the water. Otherwise, the water will become even more aggressive (corrosive); it can cause severe damage in a short period of time.

When the hardness level is low, increase the hardness immediately to limit the damage of corrosive water. You can increase the hardness level by adding a chemical like calcium chloride. When the hardness level is too high, excessive scale formation occurs, and the water may become cloudy or discolored. Elevated pH and warmer temperatures will increase scale build-up too. If the hardness level is too high, you can partially drain and refill with fresh water.

The ideal level of hardness for your pool or spa water is from 200 – 400 ppm (mg/L). You should test hardness when adding fresh water, and re-test until you have balanced the water hardness properly. After that, test hardness a minimum of once per month throughout the season. If you use calcium hypochlorite as a sanitizer, you need to test more frequently to ensure that the level has not exceeded the upper limit.



Free Chlorine


Every sanitizer has two key functions, to sanitize (kill bacteria and

all living organisms) and also oxidize (destroy contaminants and

waste). The most popular pool and spa sanitizer is chlorine.

Chlorine is also classified as a disinfectant, meaning that it is

capable of killing bacteria, algae and other organic material

instantly. All chlorine does the same thing when it is added to the

water, regardless of the type of chlorine added. It forms free

available chlorine. Free chlorine is the form of chlorine that kills

bacteria, algae and disease-causing organisms. It is the attack

dog that guards your pool against microbiotic intruders. (In

general, you wouldn’t want a dog in the pool, but this is an


You must maintain free chlorine at a sufficient level to disinfect

potential contaminants on contact. The more chlorine in the

water, the more it can sanitize and oxidize the water. (Remember

that sanitizing and oxidizing are the processes that chlorine uses

to keep the water clear and clean.) However, if the free chlorine

level gets too high, it can make the water uncomfortable for

swimmers. The trick is to keep the free chlorine level in the ideal

range. In a swimming pool, keep free chlorine at a minimum of 1

ppm (parts per million) and a maximum of 10 ppm, with an ideal

concentration of 1 to 3 ppm.

In spas the level needs to be maintained at a slightly higher level

due to the smaller volume and higher temperature. The minimum

level should be 2 ppm in a spa, again no higher than 10 ppm, and

ideally 3 to 5 ppm.




We use pH as an index to express how acidic or basic a solution

is. (The scientific definition of pH is “the negative logarithm of the

hydrogen ion concentration”.) A pH greater than 7.0 is basic, and

a pH lower than 7.0 is acidic. In pools and spas, it is important to

maintain the water in the slightly basic range of 7.2 to 7.8. The

National Spa and Pool Institute (NSPI), the industry association in

the United States, has set a standard of 7.2 to 7.6 as the ideal



If pH Is Low:

The water can corrode surfaces, metal equipment or


Swimmers and bathers can experience discomfort from

burning eyes and itchy skin.

The chlorine may dissipate more quickly.

The water may cause pitting and etching of plaster



If pH Is High:

Calcium and metals tend to come out of solution (the

opposite of dissolving) at high pH levels, creating the

potential for staining and scale formation. The calcium

and metals will actually create deposits and discoloration

on pool walls and equipment.

Swimmers and bathers can experience discomfort from

burning eyes and itchy skin.

High pH can contribute to cloudy water.


For more detailed advice on the specific chemical treatment for

your pool or spa, contact Cheap Pool Products.



Total alkalinity is the measure of the amount of alkaline buffers

(primarily carbonates and bicarbonates) in your water. These

alkaline substances buffer the water against sudden changes in

pH. Total alkalinity is considered the key to water balance. It is

the first parameter you should balance when making routine

adjustments to your water.

If you neglect to check the total alkalinity in your pool or spa, you

may have trouble balancing the pH. You may also notice that pH

fluctuates suddenly despite your best efforts to keep it in the ideal

range. If the alkalinity is too low, anything introduced to the water

will have an immediate impact on pH. Abrupt shifts in pH can

cause scaling or corrosion of metal equipment and fixtures as well

as other problems. When the total alkalinity is high, the pH has a

tendency to drift upward, causing scale to form.

Maintaining an ideal level of alkalinity will protect your pool or spa

and its equipment from the harmful effects of sudden pH

fluctuations. Think of the alkalinity as training wheels: it keeps the

pH in balance without allowing it to tip too far to either side. Of

course the pH can still drift upward or downward, but that change

will happen gradually as long as the alkalinity falls within the ideal

range. The ideal range of total alkalinity for pools and spas is

between 80 and 120 ppm (mg/L).

When the total alkalinity is too low, add sodium bicarbonate. If the

total alkalinity is too high, you can lower it by using muriatic acid

or sodium bisulfate.


For more detailed advice on the specific chemical treatment for

your pool or spa, contact Cheap Pool Products.





Bromine is a popular pool and spa sanitizer often used instead of

chlorine. Bromine has some distinct differences from chlorine.

One advantage is that bromine works better for spas / hot tubs

(with hotter water and lower water volume) than chlorine does. On

the minus side, bromine is sensitive to sunlight, deteriorating

rapidly when exposed to the sun. It can also be more expensive

than chlorine. For these reasons, bromine is less popular than

chlorine for use in outdoor pools.

There are two forms of bromine, free and combined. Together

these two are called total bromine. Both forms of bromine are

sanitizers, meaning that they can kill bacteria, algae or other living

organisms in the water. Be sure to use a test kit that measures

total bromine, since that is the best indicator of the level of

sanitizer in your water. The ideal concentration of total bromine in

a swimming pool is 3 to 5 ppm. The ideal in a hot tub or spa is 4

to 6 ppm. (In spas the level should be slightly higher level due to

the smaller volume and the higher temperature of the water.)

You have to monitor the bromine level continually, almost daily,

as it will fluctuate constantly. Environmental conditions (leaves,

rain) and usage (how many folks are enjoying the pool or spa) will

add contaminants in the water. Those contaminants will decrease

the bromine existing in the water. Be sure to test the bromine

before entering the water. Even if the system is dormant or not in

use, you should test the bromine level at least weekly to prevent

any build-up of bacteria or algae.



Total Chlorine


Chlorine in pool and spa water may be present in two forms. It is free chlorine that does the hard work of killing bacteria and oxidizing contaminants. (When you add a chlorine compound like Cal-Hypo or trichlor to your pool, you are actually adding free chlorine.) When the free chlorine combines with these contaminants, such as oils, swimmer waste and other organic compounds, it becomes combined chlorine, or chloramines. In pool and spa water, this form of chlorine has very little sanitizing ability, and no oxidizing ability. You can think of combined chlorine as a spent bullet.

Total chlorine is just the sum of both combined chlorine and free chlorine. In other words,

(total chlorine) = (free chlorine) plus (combined chlorine)

Knowing your total chlorine and free chlorine levels allow you to calculate combined chlorine (combined chlorine = total chlorine minus free chlorine). If the total chlorine level is higher than free chlorine, it is obvious that combined chlorine is present. In that case you need to shock or superchlorinate your pool or spa. To shock the pool, you add a free chlorine compound in an extra large dose. The high dosage of free chlorine will actually oxidize (destroy, burn off) the combined chlorine.