Free chlorine refers to the amount of chlorine that has yet to combine with chlorinated water to effectively sanitize contaminants, which means that this chlorine is free to get rid of harmful microorganisms in the water of your swimming pool.
Raising pool chlorine can be much easier than trying to lower chlorine levels. Simply adding chlorine in the form of chlorine tablets, granular chlorine, liquid shock or powder shock will increase the total amount of chlorine within the pool.
Total chlorine is the total amount of chlorine in the water. When chlorine binds up with contaminants it forms a compound called “chloramines” that are still part of the total but no longer effective. The chlorine that is still active to remove contaminants is known as free.
Risks of Over-Chlorination. While slightly higher-than-normal levels of chlorine in your pool are harmless, exposure to an over-chlorinated pool can have adverse effects on your health and well-being. Excess chlorine can alter the pH level of the water in the pool, making it more acidic.
The sum of combined chlorine and free chlorine is total chlorine (combined chlorine + free chlorine = total chlorine). Inexpensive chlorine tests typically show total chlorine only. Since clean chlorinated water contains no combined chlorine, total chlorine in a sanitized pool is the same as free chlorine.
"Shocking” refers to the process of adding chlorine or non-chlorine pool chemicals to the water in order to raise the "free chlorine” level. The goal is to raise this level to a point where contaminants such as algae, chloramines and bacteria are destroyed.
Think of it this way: when a chlorine compound is added to swimming pool or spa water, it reacts with water to form the compounds known as hypochlorous acid and hypochlorite ion. ... If the readings are the same, then no Combined Chlorine is present. The Total Chlorine level cannot be less than the Free Chlorine level.
Exposure to high levels of chlorine can cause lung irritation, skin and eye damage, and provoke asthma. Not only is it bad for your health, but it can be bad for your pool due to the increase in chlorine. High chlorine levels decrease the pH of your pool's water, making it more acidic.
Reasons it could be high:
Your pool has been over dosed with too much liquid or powder chlorine. Your Chlorinator is turned up too high. Your TOTAL chlorine level is high (and your FREE chlorine is low) but ineffective due to a “chlorine lock”, which happens when too much Cyanuric Acid is added to the pool.
When free chlorine is over 5.0 ppm, swimmers may experience itchy skin, irritated eyes, and/or dry hair. Pools will naturally gas-off chlorine from the surface, and very high levels can irritate airways and lungs. This is especially true for indoor pools. At chlorine levels over 10 ppm, swimsuits can begin to fade.
As mentioned above, you could probably swim in a pool without chlorine without any major health issues. However, long-term use of a pool lacking chlorinated H2O could make you sick or, at the very least, contribute to rashes and other types of skin irritation.
We're probably all familiar with at least one of the common side-effects of swimming: sore eyes, skin irritations, fading swimming costumes, and that lovely smell that lingers until you've had a good shower. But chlorine itself, when used at the recommended low levels, is perfectly safe.
No matter what type of chlorine system you choose to use for your pool, remember that the chlorine level should remain between 1.0 and 3.0 parts per million (ppm) to ensure a safe and healthy pool. If the levels are any higher, you may be at risk of swimmer's itch and red eyes.
What happens if too much shock is added? You cannot overshock a swimming pool or add too much. Adding too much shock or overshocking your pool will kill off algae. The negative of adding too much shock is it will upset the chemical balance of your pool.
Heavy shocking with granular chlorine will generally require 24-48 hours before the chlorine level has dropped to safe swimming levels (below 5 ppm). Lithium and Non-Chlorine shock labels typically allow immediate swimming, but check the package label, to be sure.
After NON-CHLORINE shock wait 10-15 minutes before entering. After chlorine shock it can take up to 24 hours to clear. Therefore it is recommended to use non-chlorine shock.
A non-chlorine shock does not disinfect the water which is why its main use is as a weekly treatment to oxidise the water and help remove contaminants and clear cloudy water. The non-chlorine shock will help your chlorine work better by creating 'Free chlorine' which is the type of chlorine needed to kill bacteria.
For many of the reasons outlined in point 2, Non Chlorine Shock can help improve water clarity fast. If you have milky or cloudy hot tub water but your chlorine levels, PH and alkalinity are ok then Non Chlorine Shock will oxidise the products causing this and help restore your water to crystal clear.
Excessive levels of pool chemicals can cause your water to become cloudy. High pH, high alkalinity, high chlorine or other sanitisers, and high calcium hardness are all common culprits.
Most people know that chlorine is an important chemical in keeping pool water safe for swimming. But adding too much chlorine can lower your pool's pH as well as its total alkalinity. When alkalinity falls, it is more difficult to maintain a stable pH.
Using liquid chlorine raises the pH of the water.
Liquid chlorine does not raise pH. When added to water, liquid chlorine (which has a pH of 13) makes HOCl (hypochlorous acid – the killing form of chlorine) and NaOH (sodium hydroxide), which raises pH.
A pH level of 7 means that water is neutral; above 7 means the water is alkaline, while below 7 indicates acidity. Aim for a pH level of between 7 and 7.6. If the water pH is higher than 8, anyone who swims in the pool is at risk of skin rashes, while a pH of lower than 7 can sting swimmers' eyes.
Ordinary household vinegar could in theory be used to lower the pH of your pool. The pH of vinegar is about 2.5, which is quite acidic when compared to your pool water. Household vinegar is very weak though (when compared to a strong acid like muriatic acid), so you would need quite a bit to lower pH.
Low pH is bad for swimmers, your pool and your wallet. Acidic water is corrosive. The most immediate effect is felt by swimmers as the water will sting their eyes, nasal passages and will dry out skin and hair, causing itching.