In a spring night in 2001, 14-year-old Rashaad Barnett was attending a poolside birthday party at a motel in St. Louis. But when the children were called in for cake and presents, no one could find Rashaad.
Police joined the search two hours later. When investigators rechecked the pool, they discovered the teen’s lifeless body. He had been there the entire time, but neither his friends nor the adult supervisors could see him because the water was too cloudy.
Such tragic stories are more common than many aquatics professionals realize. Even if lifeguards are on duty, cloudy or turbid water makes it difficult or impossible to properly scan. And drownings or near-drownings that result from turbid water leave facilities even more vulnerable to liability litigation, experts warn.
Most states have set guidelines for turbidity in public pools. The standard is crystal clear, potable water, but many have predetermined ranges from which the pool can operate. The bottom line for bather codes is the ability to see the bottom clearly.
This can be tested in several ways. Sometimes a Secchi disc — a multicolored device approximately 6 inches in diameter — is used. One has to be able to clearly see the disc on the pool bottom and discern its separate colors for the water to be acceptable. Other times, the main drain grates or other delineated markers near the bottom are used. If the pool operators can’t see the designated objects, the vessel has to be closed until the water is cleared up.
Turbid water is caused by a variety of factors, but experts say it all boils down to trouble in three areas: water chemistry, the filtration system or hydraulics. Sometimes it’s a combination of the three.
Following are some guidelines for dealing with turbid water, and its various causes and remedies.
Cause 1: Chemistry
A problem with pool water chemistry is probably the leading cause of turbid water. “It’s almost always the loss of chlorine [that causes cloudy water],” says Paul Palubicki, owner of Paul’s Pool Service in Orinda, Calif.
While chlorine is the key, several factors can play a role in cloudy pool water. Keeping the water balanced is the focal point. But to do it right, you have to use the formula for the Langelier Saturation Index:
SI = pH + alkalinity factor
- calcium hardness factor
- temperature factor – TDS factor
All of these factors, except pH, are taken from the saturation index. For example, if the water temperature is 78, calcium level is 150, TDS less than 1,000 ppm and total alkalinity (TA) is 100, we have factors of .6, 1.8, 12.1 and 2.0 respectively. These are then plugged into the formula (using the pool’s actual pH reading; let’s say it’s 7.5):
7.5 + 2.0 + 1.8 + .6 – 12.1 = 0 (SI)
Note: There is a range of acceptability between +/- .3.
Here, the SI equals zero, which means the water is balanced and the chemical equilibrium is achieved. But when one or more of these variables is off, the water will be out of balance — and it can become cloudy if calcium hardness and pH are too high.
Total alkalinity and pH can play the biggest roles in water turbidity, according to Gloria Wilson of Hasa Inc., a chemical manufacturer in Saugus, Calif. “Keeping the pH and TA under control is critical,” says Wilson, who teaches water chemistry seminars at trade shows. “A perfect pH would be between 7.2 and 7.6. For anything higher, you could possibly get minerals precipitating out, which cause the water to look cloudy.”
High TA readings also can cause minerals to fall out of solution. “TA levels should depend on what other chemicals you use in the pool,” Wilson says. “If you are using gas or [trichlor] tabs, you need a higher TA, 100 to 120. If you are using a high pH product such as cal hypo, run a low alkalinity. The lower it is, the less likely you are to bring the minerals out of the water.”
To remedy the problem of high pH and TA, various acids are utilized. Typically, you would lower pH with muriatic acid, sulfuric acid or CO. To lower TA without impacting pH, sodium bisulfate (dry acid) is used. Refer to test kit manufacturers’ instructions for specifics.
This leads to another important water chemistry factor: the sanitizer, which is usually chlorine. It’s imperative to keep chlorine levels within acceptable ranges (1-3 ppm for the typical swimming pool; 3-5 ppm for spas), so that algae blooms, which start out by making the water look milky white, and other unwanted organics stay at bay.
It’s wise to check the pool’s source water because it helps determine the type of chlorine to use. “If you know what the source is like, you won’t have to make many adjustments,” says Alison Osinski, Ph.D., owner of Aquatic Consulting Services in San Diego. “For example, if the water is hard, your first choice [for chlorine] should not be calcium hypochlorite.”
Keep in mind that chlorine’s effectiveness can be impacted by too much stabilizer (cyanuric acid) in the pool. Such conditions prolong the time it takes to kill organisms, which can lead to haziness. To remedy overstabilization, drain some of the pool water to waste (or perform a large backwash) and top off with fresh water. Or you can superchlorinate with unstabilized chlorine such as cal hypo or sodium hypo (bleach), and raise free chlorine levels to 10 ppm.
Clarifiers can be added, but everything you put into the pool contributes to total dissolved solids levels. If they’re too high, they can cause cloudy water.
“It’s a big problem in areas where there’s a lot of water evaporation,” Wilson says. “The only thing that evaporates in the pool is the water, and the only thing that stays behind is the calcium, iron, zinc, water clarifiers, stain removers and every byproduct from every chemical and person. That’s TDS.”
She points out that when TDS levels get too high, it slows down the process of other chemicals in the pool, particularly chlorine. Here again, as with overstabilization, the only solution is to drain some of the water and replace it.
Shocking won’t help. “If you shock, you’re just putting more calcium or sodium into the pool, and that just adds to the TDS,” Wilson says. “The solution is dilution.”
Cause 2: Filtration
Another culprit in the battle against turbid water frequently turns out to be the pool’s filtration system. If you suspect a problem, make sure all the valves are in the proper position to check that water can flow freely through the filter. If water is moving through the system but the filter is still not working correctly, the problem is likely on the inside. Check the internal components and see that they are in good working order.
The problem will depend on whether it’s a DE, cartridge or sand filter. “What can go wrong depends on the media,” says Bob Fowler, owner of Fowler’s Pool Service and Supply in San Diego, and a filtration class instructor at local trade shows. “You can have torn grids in a DE filter, a tear or a broken bleed tube in a cartridge filter, or a lateral break in a sand filter.”
In these instances, the water bypasses the media and is unfiltered, or filtered to a lesser degree, and returns to the pool. When this happens, cloudy water is not far behind.
Inspect the inside of the filter. Look for channeling and other media migration. You may need to poke around with a trowel or some other tool, experts say, but be careful not to damage the tank or filter components.
A test is available to check the viability of filter media, according to Osinski. After backwashing the filter, take a glass jar and fill it with 2 cups of water. Add 1 cup of media from the filter, and 1 teaspoon of dishwater detergent or water softener. Put the lid on, shake the mixture and allow it to settle overnight. It should turn into a layer of sand with water on top. However, if it settles into three layers (sand on the bottom, silt on the second layer and an organic layer on top), it is time to replace the filter media.
In addition, if you’ve noticed filter media deposits on the pool bottom near the returns, it could indicate broken laterals inside the filter. You’ll have to remove the media and inspect them. If you’re already replacing the media, this works out for the best. Replace any damaged laterals during this time.
Remember, if the filter is not being backwashed properly, small particulates can find their way into the filter bed and be carried back to the pool. Booster pumps should bring the pressure up to 50 psi on systems with automatic backwash valves.
In pools where water never seems to clear despite all of your chemical and mechanical efforts, the filter probably wasn’t sized properly in the first place. This can lead to a variety of problems.
Osinski notes that if water passes through the filter media at a faster rate than approved by NSF International and the manufacturer, debris can slip by. Use industry formulas to determine the proper filter size and see if it matches the one that has been installed. For formulas, check with the filter manufacturer. You can find the square footage of the filter tank affixed to the plate on the front of the filter. If the filter is undersized, you may need to replace it.
Finally, keep in mind that a filter actually works better if it isn’t totally clean. “A slightly dirty filter will pick up more debris, so you don’t want to overclean them,” Fowler says. “With DE and cartridge, you want to let them come up to the ‘take apart and clean’ point. Be careful with DE because you can [fill up the space between] the filter grids if you over-backwash.”
Cause 3: Circulation
Everything on a pool must be sized correctly based on its gallonage. Turnover rate will determine the flow rate, which ties into the size of the filter, pump and plumbing.
In a world where a “bigger is better” mentality seems to reign, components of the circulation system often are oversized.
“The hydraulic issues, when it comes to cloudy water, relate to turnover time and filtration issues,” Osinski says. “If you are moving the water with too much velocity, you can strip off metals and force debris through the filter media.”
Poorly sized systems are difficult to spot because they don’t always cause the same problems. “At times, [the turbidity] will be worse than others. The patrons might not see it until July, [when bather loads increase].”
A pool with a wrongly sized circulation system is not something an operator can remedy, certainly not in the short term. The limiting factor, obviously, is the pipes because they’re under the deck. However, Osinski notes several steps that can help cope with a poorly designed circulation system:
- Use covers to keep dirt and debris out, and help chlorine residues last longer.
- Construct windbreaks near the pool to help keep debris litter out.
- Add flocculants or clarifiers for a short-term solution. Overuse can add to the TDS levels, though, so be careful. If too high, they can also cause cloudy water.
- Limit the bather loads or close the pool entirely. This will allow the system to “catch up,” so the chemicals can do their work.
- If the flow rate is too high, throttle back on the pressure-side valve and let less water through.
Like anything else, an ounce of prevention is worth a pound of cure. It’s a good idea to anticipate problems before they happen. “I am a stickler for water chemistry and it bothers me when it gets cloudy,” Palubicki says. “You can have perfect water chemistry and good filtration, but Mother Nature can still mess you up. After storms, clean out the skimmers, vacuum the pool and check the chemicals. “If you stay on top of those things, you should be OK,” he adds.