Environmental Health

Pool and Spa FAQ's - Frequently Asked Questions: 

Why does my pool/spa need to be chlorinated?
Pools should be disinfected continuously by a chemical which imparts a residual effect. Chlorine is a type of "disinfectant", also called a "sanitizer". Disinfectants or sanitizers destroy living microorganisms and bacteria, preventing the transmission of disease. There are several types of disinfectants, such as chlorine, bromine, ozone and UV light. Public pools need a disinfectant with a measurable residual.

How much chlorine should I have in my pool and spa?
There are two kinds of chlorine found in pool/spa water: free (able to destroy microorganisms) and combined (unable to destroy microorganisms). Public pools and spas should have a free residual chlorine level of a minimum of 1.0 parts per million (ppm) if cyanuric acid is not used, and 1.5 ppm if a cyanuric acid is used. There should always be an operable automatic chlorinator when the pool and/or spa is open. The automatic chlorinator can be adjusted to maintain a safe level of chlorine. Chlorine should not exceed 5.0 ppm.

I know I have plenty of chlorine in the pool/spa because I can smell it and my patrons complain of burning eyes, but it doesn't show up on my test kit. Why?
Your test kit is correct - you do not have the right amount of chlorine in your water. If you smell chlorine in the water, or if you have irritated eyes from the water, you are more than likely experiencing chloramines (combined chlorine), and not free residual chlorine needed to disinfect your pool. Some test kits will allow you to test for total chlorine levels and free chlorine levels; the difference between the two being the combined levels. If trace amounts of combined chlorine is above .3 ppm, you may need to shock, or "superchlorinate" the pool to break the bond of chloramines.

What is cyanuric acid?
Also called "stabilizer" or "conditioner", cyanuric acid is added to swimming pools and spas to slow down the decomposition of chlorine from the sun's ultraviolet (UV) rays. With a correct dose, it can save up to 80% of normal chlorine consumption during peak sunny months. With an incorrect balance, it can substantially decrease the effectiveness of the chlorine. Cyanuric acid is found in most chlorine tablets, or can be added as a separate chemical.

In public pools, the cyanuric acid level should be checked and recorded at least once a month with a cyanuric acid test kit. The level should not exceed 100 parts per million (ppm). The ideal range is 30 - 50 ppm. Dilution is the only way to reduce cyanuric acid levels. If the cyanuric acid level exceeds 100 ppm, partially drain the pool while scrubbing the sides (cyanuric acid will stick to the sides), refill, and check again. For a spa exceeding 100 ppm, completely drain while scrubbing the sides, refill, and check.

What chemicals do I need to test for regularly?
Chlorine (or other approved disinfectant) and pH levels should be checked and recorded on a maintenance log at least once per day. Cyanuric acid levels should be checked and recorded at least once per month. Other chemical tests (such as alkalinity, calcium hardness, and total dissolved solids) could be checked as needed to help balance the chlorine and pH or help keep the water clear.  

My pool serviceman comes twice a week and checks the chemical levels. Do I still need to do that?
YES! The law requires all public pools and spas to have an on-site operable test kit, and a daily log of chlorine, pH levels, and other maintenance actions. You should have the basic knowledge of pool maintenance and water chemistry balance. The pool and spa areas can be dangerous if they are not operated in a safe manner, and they could be a health risk to your patrons.

When should the pool and/or spa be closed to the public?
Anytime an immediate and imminent health risk exists, the pool/spa should be closed. These could include the following: excessive water cloudiness (the main drain is not visible), no free residual level of disinfectant/sanitizer (e.g., chlorine), the filtration and/or automatic disinfection system is not operable, the covers over the main drain or the equalizer lines are broken or missing or there is a suction hazard, the underwater light fixture has water in it, chemicals are added to the water, or any time you feel there is a health risk to patrons. It is better safe than sorry.

Is there a class I could attend to better understand my pool?
Yes - there are several companies that offer a class and exam to become a National Swimming Pool Foundation Certified Pool Operator (CPO). Research the internet, consult your local pool store, or call the office for more information.

CDC: Healthy Swimming

Should you have any questions about the operation of your pool and/or spa, please call the office at 530-621-5300 in Placerville and 530-573-3450 in South Lake Tahoe.