The Importance of Water Clarity

The clarity of water in public aquatic facilities is vital for the safety of patrons. The main reason is that when pool water becomes cloudy to the point of inability to see swimmers beneath the surface, this becomes a drowning hazard. According to the Centers for Disease Control CDC, 10 people die every day due to drowning. That is over 3,000 deaths a year. Ten percent of the deaths from drowning are related to cloudy or murky water as a contributing factor. Tragically, many cloudy water drownings occur even with supervision or lifeguards present.

Here is just one tragic example: On a hot Sunday in June 2011, Marie Joseph hopped into a Toyota Corolla with a group of friends to go and cool off at the Veterans Vietnam Memorial Pool at Lafayette Park in Fall River, Massachusetts.  Two days after this, Marie’s body was found floating in the public pool at Lafayette Park.  During the outing, Joseph and a nine-year-old were playing on the slide. After sliding down together, the nine-year-old surfaced and noticed that Marie had appeared to sink to the bottom and had not surfaced! The nine-year-old notified a lifeguard that Marie Joseph was underwater and in trouble.  The responses of the lifeguards at the facility are questionable but one of the undisputed results of the investigation afterward showed that extremely cloudy pool water hid Marie Joseph from lifeguards, friends, and police investigators.

Conclusions from the investigation stated that “low visibility was the reason Marie Joseph’s body went unnoticed for two days after she drowned”. The Herald News July 1st, 2011.

A police investigation revealed that visibility in the pool was less than 4 feet below the surface.  Even though required by state law, the bottom of the pool was not visible at all!

There are numerous reports such as this that occur in public facilities and lead to drowning deaths. Even with lifeguards on duty, cloudy water can hide drowning victims. In this case, the supervision of lifeguards is useless. The main point here is that cloudy water drownings are absolutely preventable when the victim can be clearly seen.

Water clarity is important because, for public pools, there is a standard for the clarity of the water. Public pools and aquatic facilities must meet the NSF recommendation of 0.5 Nephelometric Turbidity Units NTUs. This is the same recommendation as drinking water. In other words, public pools need to be as clear as a glass of water. NTUs are measured by a device known as a nephelometer which measures the turbidity of the water in digital readouts. Health inspectors who don’t carry a device with them will use a visual means of evaluating clarity by standing on the deck and looking at the deepest part of the pool, where the main drain is usually located. The inability to see the main drain clearly is the cause for the immediate closure of the pool.

There are many causes of cloudy water. Everything from a lack of sufficient sanitizer to incorrect water balance. In particular, high Total Dissolved Solids TDS and high Calcium Hardness are two main culprits of water balance that can cause cloudy water. TDS levels should be managed so as not to exceed 1,500 ppm over the start-up water.  Excessive bather load and an influx of contaminant waste will cause pool water to become cloudy very quickly.

When cloudy water begins to become an issue, the first thing to check is the filtration and circulation system. If it is a sand filter system, check to ensure that there is a proper amount of sand in the filter tank. Also, check for mudballs in the sand media that could burrow through the sand bed and cause channeling. These are tunnels through the sand bed that will lead to unfiltered water going back to the pool.  Also, if the sand is new, it may not filter as well. In the case of brand-new sand or media, it is recommended to use a clarifier in order to make small particulate matter more filterable. Cartridge filters may need cleaning or replacement, and Diatomaceous Earth D.E. the media may need to be backwashed and replaced. Also, the grids should be checked for holes that would allow D.E. to pass through into the pool, causing haziness from the media in suspension of the water. Other things to check are the pump pots and skimmers for any accumulation of debris. Check the flow of the system to ensure there is not a clog somewhere. Also, check for suction leaks that allow air into the system.

While water clarity is important for safety it can also have an impact on the efficiency of Ultra-Violet UV systems as well. UV works by high-energy low low-intensity light waves that disrupt the DNA of microbes. Water with excessive amounts of particulate matter present will cause the light rays to deflect so they can not hit the microbes. An excess of body oils and particles can also lead to clogging of filters and interference with probes.

Regarding pool water clarity, it is better to be proactive than reactive. If the pool is already cloudy, it must be closed until the water is cleared. Proactively managing water clarity means first having the proper filtration and circulation system to ensure that the pool’s water is passing through in 6 hours. This is the standard turnover rate code. Also, ensure that the filter is sized properly to the pump’s flow. So, proper turnover, proper flow rate, and proper filter size. If you live in Nebraska, taking a CPO Certification course can walk you through how to determine all of these correct circulation and filter rates. You can find more information and sign up by clicking CPO Certification Nebraska. 

Chemical solutions include the use of a natural-based chitosan clarifier, especially for sand filters. Enzymes can break down oils that can combine with dirt and foul up filters and probes. Additional oxidation such as ozone, UV, or shocking with liquid chlorine helps to keep combined chlorine levels managed and oxidize non-living particulates. Clearwater is really the number one priority when it comes to a public aquatic facility. Proactively managing water clarity will bring increased safety to the patrons and additional peace of mind for the operator.